Abstract
BackgroundInfants are at greatest risk for pertussis morbidity and mortality. Maternal vaccination during pregnancy has been shown to prevent pertussis in young infants in high- and middle-income countries. However, data on the levels of maternal pertussis antibodies and the efficiency of transplacental transfer in low-income South Asian settings are limited.ObjectiveTo estimate the prevalence of maternal pertussis antibodies and the efficiency of transplacental transfer in rural southern Nepal.Design/methodsPaired maternal-infant blood samples were collected from a subsample of participants in a randomized, controlled trial of maternal influenza immunization (n = 291 pairs). Sera were tested by enzyme-linked immunosorbent assays for pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae. Maternal and infant pertussis antibody levels and transplacental transfer efficiency were determined and potential factors associated with both were assessed.ResultsElevated maternal antibodies to pertussis toxin, suggesting recent pertussis infection, were rarely detected (4%, tested n = 305). However, paired maternal-cord sera were highly correlated across all antibodies; transplacental antibody transfer ratios for pertussis toxin were 1.14 (n = 291, 95% CI 1.07–1.20); filamentous hemagglutinin 1.10 (n = 120, 95% CI: 1.01–1.20); fimbriae 2/3 1.05 (n = 120, 95% CI: 0.96–1.15) and pertactin 0.96 (n = 289, 95% CI: 0.91–1.00). Older gestational age was associated with increased pertussis toxin and decreased fimbriae 2/3 antibody transport.ConclusionsA low prevalence of maternal antibody to all four pertussis antigens was noted in Nepal, but transplacental antibody transfer was efficient. No consistent demographic factors were associated with elevated maternal antibody levels or efficiency of transplacental transfer. If an increase in infant pertussis disease burden was detected in this population, maternal immunization could be an effective intervention to prevent disease in early infancy.
Highlights
Epidemic levels of pertussis have been reported recently, mainly in high-income countries where acellular vaccines are exclusively used [1,2,3]
Transplacental antibody transfer to four pertussis antigens was efficient with the highest ratio of infant to maternal titers of 1.14
Recent studies of pertussis antibodies in unvaccinated mothers in various locations, including the US, Asia, and Europe, found efficient antibody transfer between mothers and infants with the following percentages of antibody seen in the infants when compared with the mothers: pertussis toxin (PT), 107–290%; filamentous hemagglutinin (FHA), 135– 183%; PRN, 120–173%; and fimbriae 2/3 (FIM), 112–157% [15,16,17,18,20,21,27,37,38]
Summary
Epidemic levels of pertussis have been reported recently, mainly in high-income countries where acellular vaccines are exclusively used [1,2,3]. The most promising strategy that has recently been implemented in several high- and middle-income countries has been the vaccination of women during pregnancy [9,10,11]. Maternal vaccination during pregnancy has been shown to prevent pertussis in young infants in high- and middle-income countries. Maternal and infant pertussis antibody levels and transplacental transfer efficiency were determined and potential factors associated with both were assessed. If an increase in infant pertussis disease burden was detected in this population, maternal immunization could be an effective intervention to prevent disease in early infancy
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