Dynamics of Respiratory Syncytial Virus Illness and Serology During Pregnancy and Infancy in the United States and South Africa.
Vaccination during pregnancy to protect infants against respiratory syncytial virus (RSV) disease relies on transplacental transfer of RSV neutralizing antibodies. Observational natural history studies on correlations between RSV-specific antibody levels and infant protection have, however, had variable results.
This observational natural history study characterized RSV-specific neutralizing antibody levels and described infant RSV disease dynamics in South African and United States (US) maternal-infant pairs. Naturally acquired RSV serum neutralizing titers were determined from 726 pregnant individuals and their infants at birth and assessed in relationship to serum neutralizing titers conferred by serum palivizumab protective levels.
In the absence of vaccination, we found no correlation between RSV neutralizing titers and infant protection against RSV-associated lower respiratory tract illness. South Africa versus US comparison revealed similar, broad distributions of maternal serum RSV neutralizing titers but lower transplacental transfer rates in South Africa (0.6 [95% confidence interval {CI}, .6-.7]) than the US (1.3 [95% CI, 1.1-1.4]) and high rates of community spread of infant asymptomatic RSV infection in South Africa versus the US.
These findings suggest that the effectiveness of maternal immunization against infant RSV relies on immunization shifting natural distribution of maternal RSV neutralizing titers into the protective range for infants, which is supported by efficacy demonstrated with RSV maternal immunization.
This observational natural history study characterized RSV-specific neutralizing antibody levels and described infant RSV disease dynamics in South African and United States (US) maternal-infant pairs. Naturally acquired RSV serum neutralizing titers were determined from 726 pregnant individuals and their infants at birth and assessed in relationship to serum neutralizing titers conferred by serum palivizumab protective levels.
In the absence of vaccination, we found no correlation between RSV neutralizing titers and infant protection against RSV-associated lower respiratory tract illness. South Africa versus US comparison revealed similar, broad distributions of maternal serum RSV neutralizing titers but lower transplacental transfer rates in South Africa (0.6 [95% confidence interval {CI}, .6-.7]) than the US (1.3 [95% CI, 1.1-1.4]) and high rates of community spread of infant asymptomatic RSV infection in South Africa versus the US.
These findings suggest that the effectiveness of maternal immunization against infant RSV relies on immunization shifting natural distribution of maternal RSV neutralizing titers into the protective range for infants, which is supported by efficacy demonstrated with RSV maternal immunization.
Authors
Madhi Madhi, Simões Simões, Klein Klein, Zareba Zareba, Dormitzer Dormitzer, Scott Scott, Gurtman Gurtman, Gruber Gruber, Jansen Jansen, Cooper Cooper, Cai Cai, Schmoele-Thoma Schmoele-Thoma, Swanson Swanson
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