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, 138 (6), 407-14

Oral Polio Vaccination During Pregnancy: No Increase in the Occurrence of Congenital Malformations

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Oral Polio Vaccination During Pregnancy: No Increase in the Occurrence of Congenital Malformations

T Harjulehto-Mervaala et al. Am J Epidemiol.

Abstract

To examine the possible association between maternal vaccination with oral polio-virus and congenital malformations of the child, use was made of a nationwide mass vaccination in Finland. During a restricted period in 1985, a vaccination with trivalent oral poliovirus was implemented with coverage of 94% of the population. The study population was chosen from three major hospitals in the Greater Helsinki Region in Finland which deliver over 95% of the children of their catchment area. One study and two reference cohorts were delineated; the former consisted of pregnancies that were in their first trimester during the vaccination period. The two reference cohorts included mothers from the same hospitals whose pregnancies were likewise in the first trimester during the corresponding time period in 1984 and 1986, i.e., 12 months before and after the study period. Each cohort consisted of approximately 3,000 mothers/children whose delivery and hospital records were manually perused by trained nurses. All the structural malformations reflecting an impaired organogenesis during the sensitive first trimester were monitored. A total of 209 (2.3%) such malformations were recorded and characterized. There were no differences between the study and reference cohorts (risk ratio = 0.7, 95% confidence interval 0.5-1.0). According to the authors' power estimate, an additional prevalence greater than 0.5% would have been detected. The authors conclude that administration of oral poliovirus vaccine during early pregnancy was not associated with an elevated risk of congenital malformations.

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