The Half-Life of Maternal Transplacental Antibodies in infants from mothers vaccinated with diphtheria, tetanus and pertussis: An individual participant data meta-analysis

Aim: There are no reliable estimates of the half-lives of maternal antibodies to the antigens found in the primary series vaccines. We aimed to calculate the half-lives of passively acquired antibodies in infants born to mothers participating in studies of tetanus, diphtheria and acellular pertussis (Tdap) vaccination during pregnancy. We aimed to determine whether decay rates varied according to maternal age, birthweight, sex, socioeconomic status, country, or vaccine received.

Methods: De-identified individual participant data from infants born to women taking part in 9 studies of maternal immunization, in 8 countries (UK, Belgium, Thailand, Vietnam, Canada, Pakistan, USA and the Netherlands) were combined. Blood samples were taken at two timepoints before any Tdap containing vaccines were received by the infant: at birth and at 2-months of age. Decay rates for each antigen were log2-transformed and meta-analysis performed. Half-lives were calculated by taking the reciprocal of the absolute value of the mean decay rates.

Results: A total of 4,091 samples were included in the analysis and there was significant variation between studies. There was significant variation in the half-lives of the 6 antigens of interest (p<0.001), with estimates ranging from 28.1 days for diphtheria to 35.6 days for filamentous haemagglutinin. The decay of maternal antibodies did not significantly differ by country-level socioeconomic status, maternal age, sex, birthweight or maternal vaccination.

Conclusion: Maternal antibodies decay at different rates for the different antigens, however the magnitude of the differences are small. Differences in laboratory techniques may account for some of the variability between studies.