Neonatal tetanus in the babies of Nigerian mothers immunised against Tetanus

Abstract

The objective of this study was to describe the clinical characteristics of babies with neonatal tetanus (NNT) whose mothers were immunised against tetanus and determine the outcome of their hospitalisation. The hospital records of babies affected by NNT whose mothers received at least two doses of anti-tetanus vaccine during pregnancy were identified and compared with similarly affected babies whose mothers were not immunised against tetanus during pregnancy in a Nigerian hospital. Out of 175 cases of NNT, the mothers of 24 (13.7%) babies were immunised against tetanus during pregnancy while the mothers of 151 (86.3%) were not. The proportions of babies of immunised mothers and unimmunised mothers who presented within the first three days of life, within a day of the onset of symptoms and with spasms were similar. Nevertheless, the survival rate was higher (62.5% vs. 26.5%; P = 0.0004) among babies of immunised mothers. Despite similarities in clinical presentation of babies of mothers with and without anti-tetanus vaccination, the survival rate was higher for the former.

Introduction

Although tetanus is a vaccine-preventable disease,¹ neonatal tetanus (NNT) remains an important cause of death in many countries.² Women vaccinated during pregnancy are capable of producing tetanus antibodies that are transported to the fetus.³ However, pregnant mothers with non-protective levels of tetanus antitoxin pose great risks of neonatal tetanus to their newborns.

The focus of the most recent drives to eliminate maternal and neonatal tetanus is improved anti-tetanus immunisation specifically directed at the high-risk populations and ensuring clean deliveries.⁴ Although great efforts have been made in the developing world to improve tetanus toxoid (TT) coverage, the burden of NNT has not significantly improved.⁵ Therefore, it may be necessary to study the immunisation status of the mothers whose babies are affected by NNT. It is also essential to study the clinical features of the affected babies. These may give a clue as to the persistence of this disease.

Methods

This is a retrospective study of babies admitted to the Neonatal Unit of the Olabisi Onabanjo University Teaching Hospital, Sagamu, Nigeria between January 1991 and December 2005, with the diagnosis of NNT. Ethical clearance was obtained from the Ethics Committee of the hospital. The data obtained from each mother-baby pair included the age and parity of the mother, place of antenatal care and delivery, details of anti-tetanus immunisation history, symptoms, details of cord care and the outcome of hospitalisation.

In this study, mothers who received at least two doses of TT vaccine during pregnancy at least two weeks before delivery or one dose of TT in addition to a previous history of TT immunisation, were regarded as immunised against tetanus while those who received no dose of TT vaccine or just one dose of the vaccine were regarded as not immunised against tetanus.

The data obtained was analysed using SPSS 15.0 software. Comparison of proportions was done with the Chi-Square test. Statistical significance was established when P values were less than 0.05.

Results

One hundred and seventy-five babies with neonatal tetanus and their mothers were studied. The mothers of 24 (13.7%) babies received at least two doses of TT vaccine in the index pregnancy. A total of 151 mothers were not immunised: 24 (13.7%) had one dose and 127 (72.6%) had no TT vaccine during pregnancy (Table 1).

Table 1

Comparison of mothers who received tetanus toxoid and those who did not

	Immunised		Unimmunised
Parameters	N = 24	%	N = 151	%	P value
Age 18–34 years	22	91.7	136	89.4	0.8
Primiparity	16	66.7	87	57.6	0.4
Grandmultiparity	3	12.5	14	9.3	0.6
Socio-economic class V	11	45.8	84	55.6	0.3
Antenatal care	16	66.7	21	13.9	0.000

Most of the mothers in both groups were primiparous (16 [66.7%] vs. 87 [57.6%]; P = 0.4).

A significantly higher proportion of the immunised mothers received antenatal care compared with mothers who were unimmunised (P = 0.000).

In Table 2, the proportions of babies of both groups of mothers who were delivered outside health facilities were similar (P = 0.7). Fifteen (62.5%) of the babies of mothers who were immunised presented within three days of age compared with 77 (51.0%) of mothers who were unimmunised (P = 0.2). There was no significant difference in the proportions of babies in both groups who presented with spasms and who presented within a day of the onset of symptoms (P = 0.5 and 0.7, respectively). There was similarity in the proportion of babies in both groups who weighed less than 2.5 kg at presentation (P = 0.4). The proportions of babies of mothers who were immunised, but had poor quality cord care, was significantly lower than that of the comparison group (P = 0.001).

Table 2

Comparison of babies of mothers who received tetanus toxoid and those who did not

	Immunised		Unimmunised
Parameters	N = 24	%	N = 151	%	P value
Age <3 days	1	4.2	3	1.9	0.5
Age >7 days	15	62.5	77	51.0	0.3
Delivery outside health facilities	20	83.3	129	85.4	0.8
Presence of co-morbidities*	14	58.3	56	37.1	0.048
Spasms at presentation	17	70.8	116	76.8	0.5
Onset^†	3	12.5	22	14.6	0.8
Poor quality cord care	5	20.8	88	58.3	0.001
Weight <2.5 kg	9	37.5	45	29.8	0.4
Survivors	15	62.5	40	26.5	0.0004
Died within 24 hours of admission	1	4.2	32	21.2	0.000
Duration of admission >1 week	17	70.3	45	29.8	0.000

*Presence of other conditions like severe anaemia, sepsis, hypoglycaemia and asphyxia

^†Presentation within one day of onset of symptoms

The survival rate among babies of mothers who were immunised was significantly higher than that of babies of mothers in the comparison group (P = 0.0004). Indeed, a significantly higher proportion of babies of mothers who were not immunised died within 24 hours of admission compared with the babies of the comparison group of mothers (P = 0.048). Similarly, a significantly higher proportion of babies of mothers who were immunised stayed on admission longer than a week compared with babies of the comparison group of mothers (P = 0.000).

Discussion

This study highlights the occurrence of tetanus disease in the babies of mothers who were adequately immunised against tetanus in pregnancy. It is expected that adequate immunisation of mothers with TT in pregnancy should confer protection against NNT.⁶ Besides logistic problems like breakage in the cold chain resulting in loss of vaccine potency, other plausible scientific explanations may include poor immune response among the immunised mothers.⁷ In addition, the amount of tetanus toxins released into the babies' circulation might have overwhelmed the passively-acquired circulating antibodies in the babies, resulting in clinical symptoms of tetanus.⁷ There may be other conditions competing for the immune competence of these mothers, thus militating against adequacy of anti-tetanus immunisation. Malaria and HIV infections, which are highly prevalent in the tropical parts of the developing world, are now associated with inadequate placental transfer of tetanus antibodies to the foetus.^8,9 Therefore, a large scale study of the immune response of mothers vaccinated against tetanus is desired. Specifically, the rate and magnitude of transplacental transfer of tetanus antibodies need to be studied. Nevertheless, the improved survival of babies of mothers who were immunised may be because maternal immunity mitigated the severity of the disease, which improved the outcome in those babies. Longer admission period of babies of unimmunised mothers may have been due to the early demise in the comparison group, as indeed more babies of unimmunised mothers died within 24 hours of admission.

Most of the immunised mothers received antenatal care, which highlights the crucial role of antenatal care in improving childhood survival. Improving access to quality antenatal care services would therefore contribute to reducing the incidence of neonatal tetanus.¹⁰

The proportion of babies of immunised mothers who had poor quality cord care was significantly lower than that of the unimmunised mothers. This may imply that mothers who were immunised had better cord care practices and this would relatively reduce the bacterial and toxin load in their babies and ultimately reduce the severity of the disease with improved survival.¹⁰

Clinical presentations of NNT were similar in babies of immunised and unimmunised mothers but improved outcome was observed in babies of immunised mothers.

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