A Cross-Sectional Analysis of 2017-2022 National Immunization Survey: Sociodemographic Disparities Associated With Human Papillomavirus Vaccine Initiation and Completion Series Among US Adolescents

Abstract

Objective

The introduction of the Human Papillomavirus (HPV) vaccine has led to future decline in prevalence of HPV-causing cancers; however, disparities in early HPV vaccine uptake and coverage may contribute to persistent inequalities in HPV-related cancers in the United States. We assess the current trend of sociodemographic factors significantly associated with the initiation and Up To Date (UTD) HPV vaccine series among adolescents in the U.S.

Methods

The retrospective National Immunization Survey-Teen data were analyzed for a cohort of adolescents aged 13-17 years who initiated HPV vaccine and completed the series from 2017 to 2022. A multivariable logistic regression estimated the correlation of sociodemographic variables to determine the odds of HPV vaccine initiation and completion as the outcomes.

Results

There were 3.2% and 5% surge in HPV vaccine initiation and UTD, respectively, with teens’ mean age of 14.98 over the years. The unvaccinated dropped by 5.6%, and those not UTD declined by 4.6% in the HPV vaccine series during this period. The proportion of teens who initiated and completed the vaccine series were mostly older female teens, non-Hispanics, regularly insured with private coverage, raised by educated older mothers, above poverty status, and living in the South. The adjusted multivariable logistic regression shows the odds of initiating and completing increases over the years, and older teens are more likely to initiate the HPV vaccine and complete the vaccine series. However, boys with non-Medicaid coverage/uninsured in the South have lower odds to initiate and complete the vaccine.

Conclusion

Improved HPV vaccine uptake and UTD were found in older females, insured with Medicaid, and from highly educated mothers in the Northeast. Findings underscore the importance of effective strategies to address current HPV vaccination disparities among identified teens with lower uptake and UTD that may reduce future burden of HPV-related cancers in the U.S.

Keywords

human Papillomavirus vaccination teen initiation completion national immunization survey-TEEN cancer prevention socio-demographic disparities

Introduction

Despite the strong evidence supporting HPV vaccine’s effectiveness in preventing HPV-related cancers,¹ a significant proportion of adolescents in the United States (US) are yet to initiate or complete the vaccine series² to prevent future incidence of HPV-related cancer. Approximately 36 000 cases of high-risk HPV associated cancers are reported annually, accounting for about 2% of all cancer types in adult males and 3% in females in the United States.^1,3 A growing public health disparity is the elevated risk of subsequent malignant neoplasms, particularly 71% of HPV causing oropharyngeal cell carcinoma with 1% yearly increase,^4,5 among adolescents and young adult survivors.⁶ In 2022, the initiated (at least 1 dose) HPV vaccination coverage among US adolescents aged 13 to 17 was 76% compared to 62.6% of Up To Date (UTD) with HPV vaccination and 89.9% who received at least 1 Tdap dose and MenACWY dose.⁷ The lower HPV vaccination coverage in adolescents increases the risk for cervical cancer diagnoses in women between ages 35-44,⁸ although the average age of diagnosis is 50.⁴ Public health advances in HPV vaccination to eradicate HPV causing cervical cancer are difficult^9–11 without increasing the access and uptake of HPV vaccine among adolescents and young adults. The access and uptake of HPV vaccine is a preventive measure recommendation to reduce future cancer occurrence and disparities.^9-12

According to the Center for Disease Control in 2023, HPV vaccines are recommended for all adolescents, with evidence demonstrating greater effectiveness when administered prior to being sexually active.^13,14 The updated HPV vaccine recommendation for adolescents according to the Advisory Committee on Immunization Practices (ACIP) includes a 2-dose schedule for immunocompetent adolescents initiating the vaccine series before their 15th birthday.¹⁴ Furthermore, it is recommended that individuals who begin the vaccination series between the ages of 15 and 26, as well as those who are immunocompromised, receive 3 doses.¹⁴ ACIP recommendations highlight the essential role of HPV vaccination initiatives in increasing HPV vaccine uptake and coverage, decreasing HPV-causing cancers, and improving health outcomes nationally, aligning with the objectives of Healthy People 2030.^13,15,16

While several studies have investigated factors influencing HPV vaccination initiation and completion,^7,9,10 comprehensive examination of recent variation in sociodemographic patterns remains limited among US adolescents.^7,11 This article explores the problem of sociodemographic discrepancies in the uptake and series completion of the HPV vaccine among U.S. adolescents leading to limited HPV vaccination coverage and potentially inadequate HPV protection. The research study aims to investigate current trends in the initiation and completion of the HPV vaccine series among U.S. adolescents, with a focus on analyzing the influence of sociodemographic factors with these trends. By examining disparities in HPV vaccine uptake, particularly between adolescents who have initiated but not completed the series and those who are fully up to date (completed the series), the research seeks to provide insights into current HPV vaccination coverage. The study also aims to evaluate progress in HPV vaccination and identify any persistent or emerging sociodemographic gaps in HPV vaccine uptake and coverage.

Methods

Study Design, Participants and Setting

The National Immunization Survey-TEEN (NISTEEN) is a representative national survey launched in 2006, of non-institutionalized young adolescents between 13-17 years of age, residing in the United States and territories at the time of interview.¹² The retrospective publicly available and deidentified HPV vaccination data for this study was obtained from the NISTEEN, survey years 2017-2022. The participants in this cross-sectional study represent adolescents between ages 13-17 years with provider-verified vaccination data and survey weights for all 50 US states, excluding teens sampled in US territories. The selected year survey (except 2017) utilized a single-frame design, ie, cellphone only, with estimates like dual-frame design nationally. All analyses in this study accounted for the complex survey sampling by utilizing the provider-phase sampling weight variable (PROVWT_C) for adolescents, which exclude US territories. This weighting will ensure adequate representation of the US population of adolescents aged 13-17 years. Overall, the survey employed techniques to reduce bias such as random digit dialing, sampling from both landline and cell-phone users in 2017, verification of immunization status by healthcare providers, and calculation of survey weights to represent the adolescent population aged 13-17 years accurately.

Eligibility Criteria and Sample Size

The NISTEEN survey includes adolescents aged 13-17 residing in the United States (excluding US territories) who have completed household interviews, with subsequent health providers’ verification. Participants are recruited through a random digit dialing (RDD) telephone survey; this method identifies eligible households with teens aged 13-17 years and adult respondents with the needed knowledge of the HPV vaccination history. The information from the household respondents were verified with healthcare providers’ record, for corresponding HPV vaccination histories through mail.

Table 1 represents the estimated sample size of HPV vaccination status of adolescents aged 13-17 years in the United States. It was derived from the total unweighted and weighted sample sizes collected from 2017 to 2022. The cumulative unweighted sample size for assessing the outcome of HPV vaccine initiation and completion among U.S. adolescents was 259,582. When survey weights were applied, the aggregate weighted sample size for the period was 126,159,575. These sample sizes are sufficient for the estimation of HPV vaccination coverage rates and trends among adolescents.

Table 1.

Total Unweighted and Weighted Sample for Each Year of HPV Vaccination Status of US Adolescents.

Sampling Year	Unweighted Sample (%)	Weighted Sample (%)
2017	43,591 (16.80%)	20,833181 (16.50%)
2018	38,706 (14.90%)	20,795755 (16.50%)
2019	43,503 (16.80%)	20,800342 (16.50%)
2020	45,008 (17.30%)	20,908256 (16.60%)
2021	45,036 (17.30%)	20,990713 (16.60%)
2022	43,738 (16.80%)	21,831327 (17.30%)
Total sample size	25,9582	126,159575

Study Variables

Dependent Variables

Information on number of HPV vaccine shots verified from the provider data were used to estimate initiation of HPV vaccine series. Initiation was defined as the receipt of at least 1 dose HPV vaccine (1+dose) while no dose (zero shot) as non-initiation / zero initiators. Adolescents were categorized as being UTD or completed the vaccine series had they received 3 doses if the series was started after the age of 15 years; or 2 doses if the series was started before age 15 years and there were at least 5 months minus 4 days interval between the first and second dose as specified by the US Advisory Committee on Immunization Practices (ACIP) guideline.

Independent Variables

The selection of sociodemographic characteristics as independent variables was based on social determinants of health influencing HPV vaccine initiation (with at least 1 dose) and UTD completion of HPV vaccination. The adolescent characteristics were age in years (in categories of 13, 14, 15, 16 and 17 years), with 13 being the reference category; sex of the adolescent was identified by the respondent and classified as female (reference), and male; race and ethnicity were categorized as Hispanics, non-Hispanic White (reference), non-Hispanic Black, Hispanic/Latino, or non-Hispanic/Latino other; the geographic census region based on true state of residence were categorized as Northeast, Midwest, South and West; the teen’s provider’s facility type included public, hospital, private, student/school/teen clinic or others and mixed facilities. The health insurance of the adolescent was analyzed based on insurance status (categorized as private only, Medicaid, other insurance and uninsured) and continuity of insurance coverage (currently insured but uninsured at some point and/or never uninsured since age 11, currently uninsured but insured at some point and/or never insured since age 11).

The family/parent or guardian characteristics as the decision makers were also examined, which include the age group of mothers in years (34 years or younger, between 35 to 44 years, 45 years or older), mother’s marital status (married and not currently married), and education level of mothers (less than 12 years, 12 years including a high-school diploma or general equivalency diploma, more than 12 years but without college graduate and college graduate). The socio-economic factors were assessed based on 2 variables, the family income level (spanning from $0 to ≥$75,000) and poverty status categorized as above and below federal poverty level using the 2017-2022 Census poverty threshold status.¹⁷

Statistical Analysis

Before conducting the analysis, we implemented the survey design and weighting provided by the NISTEEN for our sample. The weighted descriptive statistics were calculated to represent the U.S. population and account for non-response. These statistics included proportion estimates and percentages within the population of adolescents for both initiation (receiving at least 1 dose) and UTD HPV vaccination status. The analysis was conducted across 2017-2022 survey years and sociodemographic characteristics, which were the bases for the data classification to measure initiation and completion of HPV vaccine as the outcome. Multivariable logistic regression was employed to calculate both crude/unadjusted (cOR) and adjusted odds ratios (aOR) with 95% confidence intervals, to assess the association between HPV vaccine initiation and series completion and sociodemographic characteristics of the teens including maternal characteristics. Furthermore, the study assessed the consistency of association between initiation and UTD of HPV vaccination across various sociodemographic factors. The odds ratios were calculated based on the survey year and sociodemographic characteristics. A multivariable logistic regression model was utilized to estimate these associations, while accounting for potential confounding variables and other sociodemographic factors for the overall year of surveyed adolescents. Chi-square tests were performed to determine significant differences in proportion of sociodemographic characteristics across the group of outcomes.

Additionally, the interpretation of our findings focused on odds ratios with a significance level of P < .05 based on the sample size, which roughly corresponds to a small effect size upon converting the odds ratio to the r statistic.¹⁸ Meanwhile, to quantify the strength of the relationship between the dependent variables (vaccine initiation and completion) and the predictors (sociodemographic and health characteristics), the effect size equivalent for the correlation coefficient, r, was computed.¹⁸ The statistical analyses were conducted using Statistical Package for the Social Sciences, SPSS version 29 and R version 4.0.3, at a significance level (α) of 0.05.

The reporting of this study adheres to the STROBE guidelines.¹⁹

Ethical Approval

The data that support the findings of this study are available on the CDC website (https://www.cdc.gov/vaccines/imz-managers/nis/datasets-teen.html) and from the corresponding author upon request. Our study was approved by the Institutional Review Board (IRB) of Youngstown State University, with approval number 2025-37 on the 27^th of September 2024. The study did not require informed consent from participants because we utilized de-identified data from the NISTEEN, which is publicly available and does not contain any personal or identifiable information.

Result

In summary, Table 2 presents the weighted sociodemographic characteristics of adolescents aged 13-17 who initiated the HPV vaccine with at least 1 dose, and Table 3 represents those who completed the series. From 2017 to 2022, there was a rise of 3.2% in HPV vaccine initiation and a 5% increase in completion, and the average age of these adolescents was 14.98 years (SD = 1.402). Overall, approximately half the proportion of adolescents who initiated and completed the HPV vaccine were females. Nearly three-quarters of the fully vaccinated (initiated and completed) population were non-Hispanics. Dominant characteristics among the vaccinated (initiated and completed) also included White adolescents, teens who are privately insured, and teens who had current coverage. More than 90% of fully vaccinated (initiated and completed) teens were never uninsured since age 11. Additionally, the majority of the population who have initiated and completed the vaccination (nearly 40%) reside in the South region of the US, and almost half accessed healthcare providers in private facilities. Adolescents who initiated and completed HPV vaccination shared maternal characteristics such as being at least 45 years and older (approximately 50%), with college degrees, and married (approximately 61%), above federal poverty level and with family incomes over $75,000 (Tables 2 and 3). The overall proportion of adolescents who initiated with at least 1 dose of HPV vaccine and the unvaccinated (the zero initiators) in Table 2 were statistically significantly different across all demographic and socioeconomic variables. Likewise in Table 3, the proportion of adolescents who completed the vaccine series were significantly different from those who did not complete the vaccine series. (Chi-squared tests, P < .0001 at a significance level of α = 0.05).

Table 2.

Descriptive Analysis of Socio-Demographics of HPV Vaccine Initiation (Receipt of at Least One Dose) Among US Adolescents Based on Data From NISTEEN.

Weighted total	Zero Initiators N (%)	1+ Dose Initiators N (%)	Total (%)	Chi-Square Test
Weighted total	N = 35,040530 %	N = 91,119044 %	N = 126,159574 %	d.f	Value (P-value)
Variables
Year
2017	20.50	15	16.50	5	1123628.210 (<.001)
2018	18.90	15.50	16.50
2019	16.90	16.30	16.50
2020	14.90	17.20	16.60
2021	13.80	17.70	16.60
2022	14.90	18.20	17.30
Age (In years)
13	23.90	18.60	20.10	4	535784.126 (<.001)
14	20.60	19.80	20.00
15	19.40	21.10	20.70
16	18.70	20.80	20.30
17	17.30	19.60	19.00
Sex
Female	45.40	50.30	48.90	1	236959.864 (<.001)
Male	54.60	49.70	51.10	1	236959.864 (<.001)
Hispanic/Latino
Non-hispanic /Latino	79.80	73.50	75.20	1	542816.364 (<.001)
Hispanic/Latino	20.20	26.50	24.80	1	542816.364 (<.001)
Race/Ethnicity
Hispanic	20.20	26.50	24.80	3	986807.350 (<.001)
Non-hispanic black only	12.00	14.10	13.50
Non-hispanic other + multiple race	10.30	11.50	11.10
Non-hispanic white only	57.50	47.90	50.70
Census Region
Midwest	20.70	21.30	21.10	3	471523.481 (<.001)
Northeast	14.20	16.60	15.90
South	43.40	37.10	38.90
West	21.70	25	24

Weighted total	Zero Initiators N (%)	1+ Dose Initiators N (%)	Total (%)	Chi-Square Test
Weighted total	N = 35,040530 %	N = 91,119044 %	N = 126,159574 %	d.f	Value (P-value)
Variables
Facility Types for Provider
All hospital facilities	8.80	9.80	9.50	5	483637.669 (<.001)
All private facilities	44.00	45.2%	44.90
All public facilities	13.00	11.90	12.20
All other facilities	4.10	2.10	2.70
Mixed	14.80	16.60	16.10
Unknown	15.40	14.30	14.60
Insurance Coverage
Any medicaid	30.90	38.20	36.20	3	864800.138 (<.001)
Other insurance	8.20	6.70	7.10
Private insurance only	55.30	51.80	52.80
Uninsured	5.60	3.30	3.90
Continuity of Insurance
Currently insured and never uninsured since age 11	88.10	91.0	90.20	3	395002.655 (<.001)
Currently insured but uninsured at some point since age 11	6.30	5.80	5.90
Currently uninsured and never insured since age 11	1.80	1.10	1.30
Currently uninsured but insured at some point since age 11	3.90	2.20	2.70

Weighted total	Zero Initiators N (%)	1+ Dose Initiators N (%)	Total (%)	Chi-Square Test
Weighted total	N = 35,040530 %	N = 91,119044 %	N = 126,159574 %	d.f	Value (P-value)
Variables
Maternal Characteristics Mother’s AGE (years)
<= 34	7.30	7.60	7.50	2	31550.545 (<.001)
35 TO 44	44.90	43.20	43.70
>= 45	47.80	49.20	48.80
Education Level of Mothers
College graduate	42.10	43	42.80	3	494215.759 (<.001)
>12 years, non-college graduate	26.50	22.50	23.60
12 years	22	21.30	21.50
<12 years	9.40	13.20	12.20
Marital Status
Never married	33.60	39.10	37.60	1	331711.152 (<.001)
Married	66.40	60.90	62.40	1	331711.152 (<.001)
Poverty Status
Above poverty <= $75k	32.50	29.50	30.30	3	503279.011 (<.001)
Above poverty > $75k	47.40	45.0	45.70
Below poverty	14.20	19.60	18.10
Unknown	5.90	5.90	5.90
Family Income Category
$0 - $7500	1.80	2.80	2.50	11	604241.489 (<.001)
$7501 - $10000	2.30	2.90	2.70
$10001 - $17500	3.3	4.90	4.40
$17501 - $20000	3.40	4.60	4.30
$20001 - $25000	3.50	4.60	4.30
$25001 - $30000	4.50	4.90	4.80
$30001 - $35000	3.20	3.50	3.40
$35001 - $40000	4.10	4.20	4.20
$40001 - $50000	7.00	6.30	6.50
$50001 - $60000	6.50	5.70	5.90
$60001 - $75000	9.10	7.10	7.60
$75001+	51.20	48.70	49.40

N, Weighted proportion, d.f. degrees of freedom. %, percentage. Other Insurance include Chip, Ihs, Military, Or Other, Alone or In Combination with Private Insurance. Other facilities include All Std/School/Teen Clinics/ Never Married variable also include individuals who are separated, divorced, and widowed.

Table 3.

Descriptive Socio-Demographics of Up-To-Date (UTD)HPV Vaccination Among US Adolescents Based on Data From NISTEEN.

Weighted total	NOT UTD %	UTD (%)	Total (%)	CHI-SQUARE TEST
Weighted total	N = 55,241339 (%)	N = 70,918235 (%)	N = 126,159574 (%)	d.f	Value (P-value)
Variables
Year
2017	19.40	14.30	16.50	5	1404508.781 (<.001)
2018	18.40	15	16.50
2019	17.20	15.90	16.50
2020	15.70	17.30	16.60
2021	14.50	18.30	16.60
2022	14.80	19.30	17.30
AGE (in years)
13	25.20	16.00	20.10	4	1950719.545 (<.001)
14	20.80	19.40	20.00
15	19.10	21.90	20.70
16	18.10	21.90	20.30
17	16.70	20.70	19.00
Sex
Female	45.90	51.30	48.90	1	366392.850 (<.001)
Male	54.10	48.70	51.10	1	366392.850 (<.001)
Hispanic /Latino
Non-hispanic /Latino	77.50	73.50	75.20	1	270918.056 (<.001)
Hispanic/Latino	22.50	26.50	24.80	1	270918.056 (<.001)
Race/Ethnicity
Hispanic	22.50	26.50	24.80	3	524292.045 (<.001)
Non-hispanic black only	12.90	14.00	13.50
Non-hispanic other + multiple race	10.40	11.70	11.10
Non-hispanic white only	54.10	47.80	50.60
Census Region
Midwest	20.70	21.50	21.10	3	687053.994 (<.001)
Northeast	13.70	17.70	15.90
South	42.50	36.00	38.90
West	23.10	24.90	24.00

Weighted Total	Not UTD %	UTD (%)	Total (%)	Chi-Square Test
Weighted Total	N = 55,241339 (%)	N = 70,918235 (%)	N = 126,159574 (%)	d.f	Value (P-value)
Variables
Facility Types for Provider
All hospital facilities	8.80	10.00	9.50	5	726718.868 (<.001)
All private facilities	43.30	46.10	44.90
All public facilities	14.00	10.80	12.20
All other facilities	3.60	1.90	2.70
Mixed	15.4	16.70	16.10
Unknown	14.90	14.40	14.60
Insurance Coverage
Any medicaid	33.40	38.30	36.20	3	982672.250 (<.001)
Other insurance	7.90	6.50	7.10
Private insurance only	53.00	52.60	52.80
Uninsured	5.60	2.60	3.90
Continuity of Insurance
Currently insured and never uninsured since age 11	87.70	92.10	90.20	3	876733.736 (<.001)
Currently insured but uninsured at some point since age 11	6.70	5.30	5.90
Currently uninsured and never insured since age 11	1.80	0.80	1.30
Currently uninsured but insured at some point since age 11	3.80	1.80	2.70

Weighted Total	Not UTD %	UTD (%)	Total (%)	CHI-SQUARE Test
Weighted Total	N = 55,241339 (%)	N = 70,918235 (%)	N = 126,159574 (%)	d.f	Value (P-value)
Variables
Maternal Characteristics
Mother’s Age (years)
<= 34	8.10	7.10	7.50	2	286715.037 (<.001)
35 TO 44	45.80	42.00	43.70
>= 45	46.10	50.90	48.80
Education Level of Mothers
College graduate	40.80	44.30	42.80	3	465437.799 (<.001)
>12 years, non-college graduate	25.70	21.90	23.60
12 years	22.60	20.60	21.50
<12 years	10.90	13.20	12.20
Marital Status
Never married	36.50	38.40	37.60	1	43667.987 (<.001)
Married	63.50	61.60	62.40	1	43667.987 (<.001)
Poverty Status
Above poverty <= $75k	32.20	28.80	30.30	3	262758.641 (<.001)
Above poverty > $75k	45.40	45.90	45.70
Below poverty	16.50	19.40	18.10
Unknown	5.90	5.90	5.90
Family Income
$0 - $7500	2.40	2.50	2.50	11	347831.589 (<.001)
$7501 - $10000	2.70	2.70	2.70
$10001 - $17500	3.80	5.00	4.40
$17501 - $20000	4.00	4.60	4.30
$20001 - $25000	3.90	4.60	4.30
$25001 - $30000	4.60	4.90	4.80
$30001 - $35000	3.30	3.50	3.40
$35001 - $40000	4.40	4.00	4.20
$40001 - $50000	6.80	6.20	6.50
$50001 - $60000	6.40	5.50	5.90
$60001 - $75000	8.70	6.80	7.60
$75001+	49.10	49.60	49.40

The predominant demographics of unvaccinated adolescents (zero initiators) and those who did not complete HPV vaccine series (not UTD), from Table 2 and Table 3, are males, non-Hispanic/Latinos, in the US South region. The highest proportion of vaccinated adolescents utilized private facilities and had coverage from private insurance. Additionally, adolescents with mothers aged 45 and above, from married families, with income above $75,001 also revealed a significant proportion of both unvaccinated and incomplete series of HPV vaccination. Conversely, the proportion of unvaccinated individuals decreased by 5.6%, and those not UTD declined by 4.6% with the HPV vaccine series from 2017 to 2022.

The multivariable logistics regression analysis, from the adjusted model subsequently shown in Table 4 indicates that the odds of initiating the HPV vaccine series increased by approximately 77.2% over the years analyzed in this study. Additionally, Table 5 indicates that the odds of completing (or UTD) the HPV vaccine series increased by 81.8% over the years.

Table 4.

Adjusted Multivariable Logistics Regression of Socio-Demographic Characteristics Associated With Initiation of HPV Vaccine Series Among US Adolescents.

Adolescent Characteristics	OR	(95% C.I.)	r-Effect size
Year
2017	REF
2018	1.149	(1.148-1.151)	0.04
2019	1.347	(1.345-1.349)	0.08
2020	1.688	(1.685-1.69)	0.14
2021	1.867	(1.865-1.87)	0.17
2022	1.772	(1.769-1.774)	0.16
Ages (In years)
13	REF
14	1.286	(1.284-1.288)	0.07
15	1.488	(1.487-1.49)	0.11
16	1.526	(1.524-1.528)	0.12
17	1.518	(1.516-1.52)	0.11
Sex
Male	0.81	(0.809-0.811)	0.06
Race/Ethnicity of Teens
Hispanic	1.385	(1.383-1.386)	0.09
Non-hispanic white only	REF
Non-hispanic black only	1.356	(1.355-1.358)	0.08
Non-hispanic other + Multiple race	1.176	(1.175-1.178)	0.04
Census Region
Midwest	REF
Northeast	1.087	(1.086-1.089)	0.02
South	0.778	(0.778-0.779)	0.07
West	1.065	(1.064-1.067)	0.02

Adolescent Characteristics	OR	(95% C.I.)	r-Effect size
Facility Types for provider
All hospital facilities	REF
All private facilities	1.008	(1.006-1.009)	0
All public facilities	0.797	(0.796-0.799)	0.06
All Std/School/Teen clinics or other facilities	0.477	(0.475-0.478)	0.2
Mixed	1.103	(1.101-1.105)	0.03
Unknown	0.799	(0.798-0.8)	0.06
Insurance Status
Private insurance only	REF
Any medicaid	1.166	(1.165-1.168)	0.04
Other insurance	0.965	(0.964-0.967)	0.01
Uninsured	0.617	(0.615-0.618)	0.13
Insurance Continuity
Currently insured and never uninsured since age 11	REF
Currently insured but uninsured at some point since age 11	0.868	(0.867-0.87)	0.4
Currently uninsured and never insured since age 11	1.027	(1.023-1.032)	0
Currently uninsured but insured at some point since age 11	XX	XX
Maternal Age (Years)
<= 34	REF
35 TO 44	0.922	(0.921-0.924)	0.02
>= 45	0.995	(0.994-0.997)	0
Maternal Education Level
12 Years	REF
College graduate	1.244	(1.242-1.245)	0.06
<12 years	1.333	(1.331-1.336)	0.08
>12 years, non-college graduate	0.974	(0.973-0.975)	0.01
Marital Status
Married	0.869	(0.868-0.87)	0.04
Poverty STATUS
Above poverty status	XX
Below poverty status	1.045	(1.043-1.048)	0.01
Unknown
Family Income
$0 - $7500	REF
$7501 - $10000	0.754	(0.751-0.757)	0.08
$10001 - $17500	0.893	(0.89-0.897)	0.03
$17501 - $20000	0.801	(0.798-0.804)	0.06
$20001 - $25000	0.804	(0.801-0.694)	0.06
$25001 - $30000	0.692	(0.689-0.694)	0.1
$30001 - $35000	0.726	(0.723-0.729)	0.09
$35001 - $40000	0.695	(0.692-0.698)	0.1
$40001 - $50000	0.612	(0.609-0.614)	0.13
$50001 - $60000	0.611	(0.608-0.613)	0.13
$60001 - $75000	0.548	(0.546-0.55)	0.16
75001+	0.659	(0.656-0.661)	0.11

N, Weighted proportion, d.f. degrees of freedom. %, percentage. Other Insurance include Chip, Ihs, Military, Or Other, Alone or In Combination with Private Insurance. Other facilities include All Std/School/Teen Clinics/. Never Married variable also include individuals who are separated, divorced, and widowed. OR, Odds Ratio, C.I. Confidence Interval. * is P-value <0.05, Not Significant = NS, REF = Reference, X = Not Available.

Table 5.

Adjusted Multivariable Logistics Regression of Socio-Demographic Characteristics Associated With Completion of HPV Vaccine Series Among US Adolescents.

Adolescent Characteristics	OR	(95% C.I.)	r-Effect size
Year
2017	REF
2018	1.128	(1.126-1.129)	0.03
2019	1.294	(1.292-1.295)	0.07
2020	1.564	(1.562-1.566)	0.12
2021	1.778	(1.775-1.78)	0.16
2022	1.818	(1.815-1.82)	0.16
Ages (In years)
13	REF
14	1.541	(1.539-1.543)	0.12
15	1.921	(1.919-1.924)	0.18
16	2.03	(2.027-2.032)	0.2
17	2.049	(2.047-2.052)	0.19
Sex
Male	0.793	(0.793-0.794)	0.06
Race/Ethnicity of Teens
Hispanic	1.319	(1.318-1.32)	0.08
Non-hispanic white only	REF
Non-hispanic black only	1.237	(1.235-1.238)	0.06
Non-hispanic other + Multiple race	1.172	(1.17-1.173)	0.04
Census Region Recode
Midwest	REF
Northeast	1.183	(1.181-1.184)	0.05
South	0.786	(0.785-0.787)	0.07
West	0.999*	(0.997-1)	0
Facility Types for Provider
All hospital facilities	REF
All private facilities	1^NS	(0.998-1.001)	0
All public facilities	0.702	(0.701-0.704)	0.1
Other facilities	0.493	(0.492-0.495)	0.19
Mixed	1.045	(1.044-1.047)	0.01
Unknown	0.827	(0.825-0.828)	0.05

Adolescent Characteristics	OR	(95% C.I.)	r-Effect Size
Insurance Status
Private insurance only	REF
Any medicaid	1.211	(1.21-1.213)	0.05
Other insurance	0.966	(0.964-0.967)	0.01
Uninsured	0.534	(0.533-0.535)	0.17
Insurance Continuity
Currently insured and never uninsured since age 11	REF
Currently insured but uninsured at some point since age 11	0.751	(0.75-0.751)	0.08
Currently uninsured and never insured since age 11	1.011	(1.007-1.011)	0
Currently uninsured but insured at some point since age 11	xxx	xxx

Maternal Characteristics	OR	(95% C.I)	r-Effect Size
Maternal AGE (years)
<= 34	REF
35 TO 44	1.086	(1.084-1.088)	0.02
>= 45	0.962	(0.96-0.963)	0.01
Maternal Education Level
12 years	REF
College graduate	1.292	(1.29-1.293	0.07
<12 years	1.291	(1.289-1.293)	0.07
>12 years, non-college graduate	1.011	(1.01-1.012)	0
Marital Status
Married	0.953	(0.952-0.953)	0.01
Poverty Status
Above poverty status	X	X
Below poverty status	1.079	(1.076-1.081)	0.02
Unknown	X	X
Family Income
$0 - $7500	REF
$7501 - $10000	0.912	(0.909-0.915)	0.03
$10001 - $17500	1.203	(1.199-1.206)	0.05
$17501 - $20000	1.023	(1.02-1.026)	0.01
$20001 - $25000	1.097	(1.094-1.101)	0.03
$25001 - $30000	0.991	(0.988-0.994)	0
$30001 - $35000	1.068	(1.064-1.072)	0.02
$35001 - $40000	0.914	(0.91-0.917)	0.02
$40001 - $50000	0.922	(0.919-0.925)	0.02
$50001 - $60000	0.876	(0.872-0.879)	0.04
$60001 - $75000	0.793	(0.79-0.796)	0.06
75001+	0.953	(0.95-0.956)	0.01

N, Weighted proportion, d.f. degrees of freedom. %, percentage. Other Insurance include Chip, Ihs, Military, Or Other, Alone or In Combination with Private Insurance. Other facilities include All Std/School/Teen Clinics/. Never Married variable also include individuals who are separated, divorced, and widowed. OR, Odds Ratio, C.I. Confidence Interval. * is P-value <0.05, Not Significant = NS, REF = Reference, X = Not Available.

Older adolescents were 1.5 times more likely to initiate and twice likely to complete the HPV vaccine series. Furthermore, teens identifying as Hispanics, non-Hispanic Black teenagers, and teens with multiracial identity, living in the northeast region of US, with Medicaid coverage, raised by mothers who are college graduates, or mothers with less than 12 years of education, and from families below federal poverty level are positively associated with initiation and completion of HPV vaccine series with negligible effect size.

Adolescents accessing provider’s facilities (like public, student/school and unknown facility) and those uninsured (38% or approximately) or with other insurance coverage, including those currently insured but uninsured at some point, and adolescents in the south region (22% and 21%) also had lower odds of both initiating and completing the vaccine series. Additionally, teens with mothers who were married, mothers aged 45 and above, or family incomes up to $75,000 had negative association with both initiating and completing the HPV vaccine series. Overall, the level of association of these factors with initiation and completion of HPV vaccination are statistically significant at P < 0.01.

Interestingly, Table 4 and Table 5 show adolescents from families with incomes ranging from $10,001 to $35,000, and those with mothers aged 35 to 44 years, were less likely to initiate but more likely to complete the vaccine series if initiated. Similarly, those whose mothers had non-college degrees, but more than 12 years of education, exhibited a comparable trend. In both the adjusted and unadjusted model (check Appendices), the majority of these associations were statistically significant at P < 0.05; however, the effect sizes determined by Pearson’s correlation coefficient demonstrated relatively low strength and magnitude of association, particularly, ranging from 0 to 0.18.

Discussion

Sociodemographic Disparities in the Initiation of HPV Vaccination

Over the 6 years in this study, the odds of initiating HPV vaccination have noticeably increased, with 2021 marking the highest. The adolescent’s age appears to play a role in this trend, as older adolescents between ages 14 and 17 are more likely to initiate vaccination. We also found the impact of ethnicity and race, with Hispanic adolescents being more likely to initiate vaccination compared to non-Hispanic Whites. Non-Hispanic Black adolescents and those of multiple races also demonstrate higher tendencies of HPV vaccine initiation. A similar upward trend was reported in a study that investigated a10-year trend in initiation at ages 9 to 12 years and completion of HPV vaccination before age 13, especially among non-Hispanic Black and Hispanics in the US.²⁰ Our findings reinforce the progress of Healthy Peoples, 2030 towards achieving 80% target proportion of adolescents aged 13 through 15 years who received doses of HPV vaccine in line with ACIP recommendation.^13,15

Adolescents in the Northeast region of the US appear to have positive correlation with initiation, as those in the West regions although at a weak level of correlation, despite exhibiting higher proportion of the vaccine initiation. This relationship partly confirms findings from previous studies. HPV vaccination among the adolescents and older adults increased between 2007 and 2014, with the greatest increase occurring in the Northeast,²¹ and Western region in 2016 according to an investigation of geographical disparities in HPV herd protection in the U.S.²

Results from this current study suggest that adolescents under Medicaid coverage and those from families below poverty status are positively associated with HPV vaccine initiation, which deviates from research reported in 2023, yearly surveillance on HPV vaccine initiation and completion.⁷ According to the report, there was a 3.3% decline in HPV vaccination initiation among adolescents insured by Medicaid in 2022 compared to 2021.⁷ Furthermore, contrary to our findings, the 2023 yearly surveillance report also identified variation in HPV vaccination coverage to be lower among adolescents below the poverty line.⁷ However, a 2021 systematic review indicates that public insurance, like Medicaid, can help facilitate vaccine initiation and completion.²² Additionally, while some studies suggest that adolescents living below the poverty lines are more likely to start the HPV vaccination but less likely to complete the series, others report higher completion rates among those residing in high-poverty areas.²²

Lastly, maternal education seems to play a role, with adolescents whose mothers hold a college degree or less than 12 years of education being more inclined to initiate vaccination compared to those whose mothers hold a high school level of education. Although our study demonstrated a very low meaningful effect of the association, the results of our findings agree with previous literature regarding association of maternal characteristics such as age, educational level, and marital status with HPV vaccine initiation in adolescents. The study indicates mothers with college degrees, and those with less than 12 years educational level, have higher odds to have their teens initiate HPV vaccination.²³

Sociodemographic Disparities in the Completion of HPV Vaccination Series

According to our analysis, there is a noticeable time trend indicating that in 2022, teenagers are almost twice as likely to be UTD with the HPV vaccine compared to 2017. Moreover, older teens, between the ages of 15 to 17, are twice as likely to complete the vaccine series than 13 year olds, regardless of the conditions. We also found that Hispanic teens, and teens of Other or Multiple races are more likely to be UTD compared to White teens. Adolescents from families below the poverty line show a slightly higher odds of being UTD, as do families earning between $10,001 and $17,500. In terms of health insurance coverage and continuity, adolescents with Medicaid were 21.1% greater odds of being UTD than those with private insurance. Furthermore, we found that adolescents whose mothers are aged 45 years or older and those whose mothers have a college education, or less than 12 years of education, are more likely to be UTD with the HPV vaccine. Finally, adolescents accessing different (designated as mixed facilities) facilities achieve higher completion rate than those using the hospital and public facilities.

While our findings confirm the results of most previous studies, other previous studies have a differing outcome from their investigations based on the factors impacting initiation and completion of the HPV vaccine series. This would be further explored in our successive discussion pertaining variables negatively influencing both completion and initiation of HPV vaccine uptake and coverage.

Sociodemographic Disparities Negatively Associated with Initiating and Completing HPV Vaccine Series

This current study also explores factors associated with non-initiation and non-completion of HPV vaccine among the U.S. teens. After controlling for all variables, factors such as being male, residing in the South region, belonging to either low- or high-income families, receiving vaccines from any providers’ facilities (except mixed facilities), any health insurance (except Medicaid), and being raised by married, non-college graduate mothers (particularly age above 44 years) consistently show a negative correlation with HPV vaccine series initiation and completion. Furthermore, the negative correlation between age and married status of the mothers of these teens with HPV vaccine initiation and completion may be attributed to lack of intent and change in perception. Findings from a nationwide cross-sectional analysis of a previous study identified a mother caregiver and reasons, such as safety concerns, not recommended by healthcare provider, not needed/not necessary due to lack of sexual activity and ‘already vaccinated,’ influencing lack of parental intent to initiate and complete HPV vaccine series among the adolescents.²⁴ While this previous study demonstrated mother as caregiver having negative association with parental intent to vaccinate even with provider recommendation, the study failed to give account of the mother’s age and marital status. However, another cross-sectional study in 2020 proposed generational gap in the perception of vaccine benefits as an explanation for advanced maternal age being a strong determinant of HPV vaccination and being married having no significant association.²³

According to a global estimate in 2019, a higher percentage of girls than boys completed the full course of HPV vaccine worldwide.²⁵ This current research corroborates our findings when compared to females, males (regardless of their socioeconomic status or healthcare coverage) had a very low odds of initiation and completion with HPV vaccinations. Another study that investigated the reason for low series completion among adolescent males suggested the influence of facilitating discussion on HPV prevention by healthcare providers and enhancing HPV vaccination among boys.^26,27

Geographic disparities in HPV vaccination uptake and coverage have been observed. Studies have shown that adolescents in the Southern states, particularly in the South and Midwest regions, have had lower HPV vaccination rates compared to Northeastern and Western regions of the U.S.^2,21,22 The result from our analysis also supports these previous studies; additionally, adolescents from the South who receive vaccinations from all facility types (except mixed facilities) for providers show lower odds of initiation and completion with HPV vaccination series. While the West shows a slightly greater chance (crude odds ratio of 1.044) than the Midwest, there is no notable difference in the adjusted model. However, a study that examined HPV vaccination among younger and older teens found out that initiating adolescents who were uninsured or received vaccinations from public facilities had lower completion rates compared to those who were privately insured or received vaccinations from private facilities.¹⁰ Minihan and cohorts concluded that the differences are not statistically significant,¹⁰ with the result of our findings suggesting negligible effect size associated with the 2 outcomes.

Meanwhile, from our analysis, adolescents covered by other insurance different from private coverage, and the uninsured ones have lower odds of initiating and completing vaccine series. This finding confirms the result of a study where HPV vaccine series completion and timely series completion were less likely among adolescents without private insurance.²⁷ However, there is deviation in health insurance coverage among adolescents from ethnic minority group showing negative association with HPV vaccine series completion which is different from the result of our findings earlier in this chapter.²⁷ Mansfield et al. (2021) explained the variation may be due to generalizability of the study as identified in the research.²⁷ Further in our analysis, we found any interruption in continuity of insurance coverage since age 11 led to a reduction in chances of HPV vaccine initiation and being UTD. The result identified adolescents who are currently insured but were uninsured at a point since birth or age 11, and those who interrupted the continuity of health insurance coverage are associated with non-completion of their HPV vaccine series.

Considering parental/household factors associated with non-initiation and non-completion of HPV vaccine shows that adolescents from high income families with maternal characteristics such as married, and non-college graduate with more than 12 years of education are less likely to initiate and keep up with their HPV vaccine series. However, according to a study, there was no significant difference in HPV vaccination uptake between mothers who were married and those who were never married.²³ Additionally, we found socioeconomic status to adversely affect vaccine uptake and coverage, with teens from all family income categories negatively influencing initiation while those from only high income negatively influence HPV vaccine completion. There is a little deviation from findings of a systematic review conducted in 2021, which shows adolescents living in high income households were less likely to initiate HPV vaccination compared to those in low-income households.²² While the significance levels fell below 0.05, the effect sizes remained small overall. The sole exception was adolescents from the West, who exhibited no effect size and were not statistically significant.

It is important to acknowledge limitations such as low response rate in the questionnaires (missing values designated by ‘NA’) in the survey, relying on self-reported or provider records for HPV vaccination status. This limitation is crucial in examining HPV vaccination coverage among adolescents aged 13-17 years in a nationally representative data. The approach may introduce inaccuracies or reporting bias into the data, which could lead to overestimation or underestimation of actual vaccination uptake and coverage, thus, impacting the generalizability of the data. It is critical to address these limitations to ensure that public health policies and interventions aimed at improving vaccination coverage among adolescents are informed by accurate data. This improvement may involve implementing targeted outreach programs, enhancing data collection methods, and addressing barriers to vaccination access and acceptance within underserved communities.

Conclusion

Overall, the current study provides valuable insights into the factors that may contribute to HPV vaccine initiation and completion. The findings underscored disparities in HPV vaccine uptake and coverage based on demographic and socio-economic characteristics of teens aged 13-17 in the U.S. Furthermore, these results emphasize the significance of targeted interventions to address disparities in HPV vaccination coverage among teen boys, teens living in the South and Midwest, non-Hispanic Whites, teens from high-income families, teens above federal poverty level, teens who are privately insured, and the uninsured ones. Public health efforts might consider the intersectionality of socioeconomic and demographic factors in designing strategies to improve HPV vaccine uptake. By addressing barriers related to access to healthcare facilities, gender, insurance coverage and continuity, race/ethnicity, and geographic location, healthcare providers and policymakers may work towards achieving higher HPV vaccination coverage among US adolescents, ultimately reducing the burden of HPV-related diseases in this population.

Supplemental Material

Supplemental Material - A Cross-Sectional Analysis of 2017-2022 National Immunization Survey: Sociodemographic Disparities Associated With Human Papillomavirus Vaccine Initiation and Completion Series Among US Adolescents

Supplemental Material for A Cross-Sectional Analysis of 2017-2022 National Immunization Survey: Sociodemographic Disparities Associated With Human Papillomavirus Vaccine Initiation and Completion Series Among US Adolescents by Atinuke Ibrahim-Ojoawo, Nicolette Powe, Richard Rogers, Ken Learman, and Heather Hefner in Cancer Control

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical Statement

ORCID iD

Atinuke Ibrahim-Ojoawo

Data Availability Statement

The data that support the findings of our study are publicly available through the Centers for Disease Control and Prevention (CDC) website at , accessible under the National Immunization Survey-TEEN (NISTEE) datasets. There are no restrictions on the availability of these data.

Supplemental Material

Supplemental material for this article is available online.

Appendix

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