Susceptibility of Rubella Among Pregnant Women Attending the Antenatal Clinic in a Tertiary Care Hospital,Jabalpur,Central India

Abstract

The purpose of this study was to evaluate rubella susceptibility of pregnant women from central India as rubella infection can be devastating for the newborn if it occurs in the mother in the first trimester of pregnancy, which may lead to congenital rubella syndrome (CRS). There are very few studies about seroprevalence of rubella from India and none from central India. The study was conducted among women attending the obstetric department of a tertiary care hospital, in which 369 antenatal cases were tested for the presence of immunoglobulin G antibody for rubella and its titer. Data were analyzed using statistical tests. A total of 141 (38.2%) women were found susceptible to rubella. There was no significant difference in rubella susceptibility among different socioeconomic classes, ages, and gravidity. A large proportion of pregnant women were found to be rubella susceptible, posing immense threat of CRS to their newborns. A robust program for rubella immunization targeting young adult women is needed to avoid CRS.

Introduction

Rubella is a viral exanthema of childhood that is generally subclinical and inconsequential, but it may have devastating teratogenic effects known as congenital rubella syndrome (CRS) when it occurs in the first trimester of pregnancy, making rubella a virus of public health importance (18). Rubella infection during pregnancy may also lead to miscarriage and fetal death (8,18). Vynnycky et al. estimated 105,000 CRS cases globally in 2010 with the highest number of cases predicted in Africa (39,000) and Southeast Asia (49,000) (17). The incidence rate of CRS in developing countries ranged from 0.4 to 4.3 per 1,000 live births (9).

The syndrome of congenital abnormalities following maternal rubella infection has been recognized more than 50 years from now; although rubella is a vaccine-preventable disease, its immunization rates are quite suboptimal and infections during pregnancy are reported very frequently (4). There has been steady increase in the control of rubella and CRS. During 2000–2014, reported rubella cases declined 95%, from 670,894 cases reported in 2000 in 102 countries to 33,068 cases reported in 2014 in 162 countries (10). A total of 140 (72%) of the 194 World Health Organization (WHO) countries have introduced rubella-containing vaccine (RCV) and among these 140 countries, the first RCV dose was provided with the first routine dose of measles-containing vaccine in 137 (98%) countries (10). WHO member countries in the Southeast Asia region adopted a resolution to eliminate measles and control rubella by 2020, and 6 of 11 countries have introduced RCV in their National Immunization Program (2). Rubella vaccine is available in the private sector in the country and is commonly administered as measles, mumps, and rubella vaccine, which is not a part of the National Immunization Schedule in India (16).

There is no systematic review available addressing the prevalence of rubella in India, and the reported figures vary from 53% to 94% (6,9,11,14). This prevalence is relatively high in comparison with some other countries of the Asia–Pacific region (1,5 –7). Therefore, efforts are needed to reduce rubella susceptibility among pregnant women.

Rubella immunoglobulin G (IgG) test is employed to ascertain the immunity of a woman to rubella due to immunization or childhood infection (18). Although, the endemicity of rubella is well established, rubella infection and CRS are not reportable diseases in India, thus the national prevalence of both is unknown. Protective immunity to rubella in pregnant women can indirectly hint at the risk of acquiring CRS. Although a steady rise in rubella immunity, up to 87.9%, over the years is reported from India (5,8), it is also observed that 1–15% of all infants suspected to have intrauterine infection were found to have laboratory evidence of CRS (8). In a study from north India, a significant correlation was found between in utero infection of rubella and CRS in newborns (9). Therefore, an effective national-level rubella vaccination program is awaited in India, which will be helpful to control CRS.

Serosurveys are used to assess the epidemiological pattern of rubella in a community, very few such surveys have been reported from India (14). The studies conducted in the past in other parts of the country report vast differences in rubella seropositivity, making area-specific study an important aspect to undertake to estimate rubella immune status. Moreover, no such information is available from central India. This study was planned with the aim to determine the susceptibility for rubella infection among pregnant women attending the obstetrics department of a tertiary care hospital in Jabalpur, central India.

Materials and Methods

Study design and participant inclusion criteria

This cross-sectional study was carried out at Virus Research and Diagnostic Laboratory (VRDL) of National Institute for Research in Tribal Health, Jabalpur, in the state of Madhya Pradesh, India. Pregnant women aged 18–40 years attending the obstetrics department of Netaji Subhash Chandra Bose Medical College and Hospital, a tertiary care hospital of Jabalpur, were recruited for this study after their written consent. Two-milliliter venous blood samples were taken from pregnant women who consented to the study. Samples were collected till we achieved the desired sample size as explained below from February 2013 to March 2014.

Exclusion criteria

Pregnant women who were having some known clinical complications and those not willing for consent were excluded from the study.

Sample size

The sample size was calculated using standard statistical tools, considering the prevalence of rubella susceptibility among pregnant women, which ranges from 5% to 40% in studies earlier, reported from other parts of India (5,13). Thus, assuming 30% seronegativity, 10% absolute error, 5% level of significance, and design effect of 3, the minimum required sample size of 311 serum samples was calculated.

Data collection

The demographic and clinical information was collected in predesigned formats. The history of rubella vaccination was self-reported as there was no documentation of vaccination available for verification.

Laboratory investigation

All the samples were transported to VRDL in cold chain (4–8°C); serum was separated by centrifugation at 3,000 rpm at 4°C and stored at −20°C until tested. Serum was subjected to rubella antibody IgG detection by means of enzyme-linked immunosorbent assay (ELISA) using commercially available kit, Enzygnost Rubella IgG, manufactured by Siemens, Germany, following the manufacturer's instructions. The determined IgG level of samples was used as the threshold for rubella susceptibility. As per kit instructions, samples having antibody titers less than 15 IU/mL were considered susceptible to rubella infection.

Statistical analysis

Data collected were entered in Microsoft Excel 2007 for primary analysis. The statistical analysis was done using the software, statistical package for the social sciences (IBM SPSS Statistics for Windows, Version 20.0; IBM Corp., Armonk, NY). To study the association of different possible explanatory variables with unprotection against rubella in the study population, we used univariate and multivariate logistic regression techniques. Odds ratios (ORs) were computed with 95% confidence interval (95% CI) and p < 0.05 was considered as statistically significant.

Results

A total of 369 samples were collected and tested. The age of participants ranged from 18 to 40 years. Most of the antenatal cases (249 of 369) enrolled were primigravidae (first pregnancy). Fifty-one percent cases (190) were in second trimester, and 33% (123) and 11% (39) were in third and first trimester, respectively. Two hundred one (54%) cases were from urban areas and 168 (46%) were from rural setting. Most of the cases (265) were in the age group of <24 years. The average age of primigravida was 22.3 (±3.2) years, whereas in case of multigravida, it was 25.3 (±3.8) years. About 60% cases (186/312) were having monthly income less than INR 3,000.00 and were considered as the lower socioeconomic group (Table 1). None of the participants could recall and inform about their history of rubella vaccination or infection.

Table 1.

Immune Status of Pregnant Women Based on Different Parameters Such as Age, Parity, and Trimester

Variable	n	Unprotected	Percentage (95% CI)	Univariate OR (95% CI)	Multivariate OR (95% CI)
Age (years)
≤24	265	99	37.4 (31.7–43.3)	0.88 (0.55–1.40)	0.91 (0.53–1.57)
>24	104	42	40.4 (31.5–49.9)	1.00	1.00
Parity (pregnancy)
First	249	94	37.8 (31.9–43.9)	1.00	1.00
Higher	120	47	39.2 (30.9–48.1)	1.06 (0.68–1.66)	1.06 (0.63–1.78)
Trimester
First	39	13	33.3 (20.6–49.0)	0.81 (0.38–1.73)	0.70 (0.30–1.62)
Second	190	74	38.9 (32.2–46.0)	1.03 (0.65–1.64)	1.10 (0.66–1.84)
Third	123	47	38.2 (30.1–47.0)	1.00	1.00
Unknown	17	7	41.2 (21.6–63.9)	NC	NC
Place of residence
Urban	201	79	39.3 (32.5–46.2)	1.11 (0.73–1.69)	0.98 (0.61–1.56)
Rural	168	62	36.9 (29.9–44.4)	1.00	1.00
Monthly income
≤3,000	186	71	38.1 (31.5–45.3)	1.15 (0.72–1.84)	1.18 (0.73–1.92)
>3,000	126	44	34.9 (27.1–43.6)	1.00	1.00
Unknown	57	26	45.6 (33.3–58.4)	NC	NC
Total	369	141	38.2 (33.4–43.3)

95% CI, 95% confidence interval; NC, not computed; OR, odds ratio.

The ELISA results demonstrated that 228/369 (61.8%) pregnant women were immune protected against rubella and remaining 141 (38.2% [95% CI 33.4–43.3]) were rubella susceptible either having no antibody or suboptimal level (≤15 IU/mL) of IgG antibody (Table 1). Rubella IgG antibody titers ranged between 0.0 and 256 IU/mL with the mean of 52.6 IU/mL.

Rubella susceptibility was higher, 42.3%, in the higher age group (>24 years) when compared with the younger age group (≤24 years) where it was 37.3% (OR, 95% CI = 0.91, 0.53–1.57). Rubella susceptibility was found to be higher in second and third trimester cases (∼38%) when compared with first trimester cases (33.3%) (OR, 95% CI = 0.7, 0.3–1.62). It was also higher in lower socioeconomic group (38.17%) when compared with higher socioeconomic group (34.92%; OR, 95% CI = 1.18, 0.73–1.92). Rubella susceptibility was almost equal in primigravida (37.75%) and multigravida (39.16%; OR, 95% CI = 1.06, 0.63–1.78). It was slightly lower in rural cases (36.9%) when compared with urban cases (39.3%; OR, 95% CI = 0.98, 0.61–1.56; Table 1). However, all these differences were found to be statistically insignificant (p > 0.05).

Discussion

This study, for the first time, demonstrates immunoprotection to rubella in pregnant women from central India. In this study, 228/369 (61.8%) pregnant women who had no history of vaccination were immune protected for rubella. This high positivity in the absence of a vaccination program shows ongoing transmission of rubella in this part of India. A study from Jammu, north India, reported that 32.7% school-going adolescent girls were seronegative for rubella IgG (13). Various other studies from India have reported rubella seropositivity ranging from 53% to 94% (6,9,11), our result corroborates the range. Natural infection during unrecognized transmission due to mild presentation and asymptomatic infections owing to continuous circulation of rubella virus could account for such high seropositivity as none of the study participants had history of vaccination.

It is worth noting that although the participants were naturally exposed to rubella, 38.2% had antibody titers less than 15 IU/mL and thus had no protection against rubella. Factors such as individual's immune response, age of infection, and amount of virus load at the time of natural infection and presence of cross-reacting antibodies due to other infection at the time of testing could be attributed to this uneven response. To avoid risk of CRS and uncertainties, routine vaccination or second dose for girls in early teens to prevent rubella infection during pregnancy is followed in developed countries such as Canada, Singapore, and United States (3,7,12). It will be interesting to explore the reasons for varied response that will help in designing an appropriate vaccine strategy for India, especially when the country is aiming for universal vaccination.

In the studied population, 61.8% were found immune to rubella and 38.2% were rubella susceptible, this finding is in agreement with previous findings (6,14). Some other studies have also reported higher seropositivity for rubella (11). Our findings reveal that more than one-third women who became pregnant were susceptible to rubella infection. Considering 21.8 births per 1,000 population as the current crude birth rate of India, an estimated 12.1 million rubella-susceptible women get pregnant every year, putting their children at a high risk of CRS; similar figure for Madhya Pradesh (central India) comes to around 0.9 million.

In contrast to the findings of the earlier study (15), we observed a slight decrease in immune-protection with the increasing age. Furthermore, it was observed that multigravidae were having marginal extraprotection when compared with primigravidae, both these observations indicate that a sizeable number of women were infected by rubella during their child-bearing age or during pregnancy.

Although few studies have reported differences in susceptibility in rural verses urban and lower verses higher socioeconomic classes (14,15), we did not observe statistically significant differences in either of the parameters, probably because our cohort was belonging to the lower socioeconomic group (i.e., max income INR 10,000 per month) and most of our study participants in the urban group were from areas where living conditions are comparable with rural settings.

According to WHO, CRS rates are highest in the WHO African and Southeast Asian regions where vaccine coverage is lowest (18). Recently, CRS and rubella cases were detected in Canada even after 97% vaccine coverage; however, the reported cases were determined to be nonendemic (12). There are very few reports describing outcome of pregnancy in rubella-susceptible cases from India. A longitudinal study of children of mothers, who are seroconverted during pregnancy, would aid in gauging the exact CRS burden in this highly seronegative area.

Conducting the study in the constricted socioeconomic group and not following all cases to determine pregnancy outcome are few of the limitations of the study. Nonetheless, this study gives enough rationale to initiate a robust vaccination drive against rubella especially in young adult women.

Determination of population-level immunity by serosurveillance programs and population susceptibility profiles is essential, and the authors understand the challenges ahead. In the absence of rubella surveillance data, understanding regional epidemiology of rubella virus is difficult and it is difficult to device a national strategy to reduce the morbidity mortality because of rubella infections (8). Mechanisms are needed to identify and vaccinate nonimmune women in developing countries where a national immunization program is not yet implemented. It is crucial to evaluate the susceptibility to rubella virus in women of reproductive age group in direction to established policies for the prevention of rubella and CRS.

The analyses revealed that none of the explanatory variables had a significant association with unprotection against rubella in the study population. This illustrates that unprotection against rubella is almost uniformly prevalent in the study population, irrespective of their age, parity, trimester, and other socioeconomic background. Even though the Government of India has announced inclusion of rubella vaccination in its universal immunization programme for children <5 years, it is going to take time to reduce CRS morbidity. Hence, immunization is recommended indifferently especially for young adult women of all classes, areas, and ages who are planning to become pregnant, which can be accomplished with a well-planned, large-scale publicity campaign for persuasion of vaccination.

Conclusion

A large proportion of pregnant women were found to be rubella susceptible, posing immense threat of CRS to their newborns. A robust program for rubella immunization targeting young adult women is needed to avoid CRS.

Ethical Statement

This study was undertaken as part of the virology research and diagnostic laboratory (VRDL) network project. This project has approval of institutional ethics committee. All patients included in this study gave informed written consent.

Footnotes

Acknowledgments

Authors thank the Secretary to Government of India, Department of Health Research, Ministry of Health and Family Welfare, and the Director General, Indian Council of Medical Research (ICMR), for financial support under the ICMR Virology Diagnostic Laboratory network project (Grant No. VIR/43/2011-ECD-1). Authors thank the Director, National Institute for Research in Tribal Health, Jabalpur, for her support and encouragement. The authors also thank study participants. The assistance provided by staff of virology laboratory in conducting enzyme-linked immunosorbent assay is acknowledged.

Author Disclosure Statement

No competing financial interests exist.

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