Breaking News: Covid-19 vaccination during pregnancy associated with lower infant hospitalization.
Infants under 6 months old of mothers who vaccinated during pregnancy benefitted.
A new paper in the Center for Disease Control and Prevention’s Morbidity and Mortality Weekly Report found that infants up to 6 months of age who were hospitalized for Covid-19 were far less likely to have mothers who received Covid-19 vaccination during pregnancy than those in a comparison group.
Researchers compared the characteristics of mothers whose infants were hospitalized primarily for Covid-19 to infants simultaneously hospitalized for other reasons. The apparent vaccine effectiveness of maternal vaccination during pregnancy was 61% for protecting their infants against subsequent hospitalization primarily for Covid-19.
In addition, among Covid-19 cases occurring in infants of mothers who were vaccinated during pregnancy, the resulting hospitalizations were milder than those in infants of unvaccinated mothers. Intensive care admission was 44% more common among infants of unvaccinated mothers. Mechanical ventilation (i.e. intubation) was 92% more common among infants of unvaccinated mothers. One infant in the study required lung bypass (“ECMO”) and another died. Both of these tragic cases occurred in infants born to unvaccinated mothers.
Racial disparities were noted, with White women more highly represented in the comparison group than in the group with infants who were hospitalized for Covid-19. The opposite finding was reported for Black and Hispanic women. This matches known Covid-19 vaccination disparities.
The researchers also looked at whether the timing of vaccination made a difference in outcomes and found a difference. Infants of mothers who completed the 2-dose Covid-19 vaccine series early in pregnancy (before 21 weeks) did not confer statistically robust protection against infant hospitalization in the months after birth. (The vaccine effectiveness against subsequent infant Covid-19 hospitalization was 32% among infants whose mothers were vaccinated before 21 weeks, but the “confidence intervals” were so wide, that it’s possible that the real rate of protection is negligible.) Meanwhile, infants born to mothers who completed their Covid-19 vaccination series after 21 weeks enjoyed an apparent 80% vaccine effectiveness against Covid-19 hospitalization.
The design of this study has some inherent weaknesses, which should be acknowledged. Because it was not randomized (it tracked outcomes of infants by the reported vaccination status of the mothers), it’s possible that some other unrelated characteristics of the unvaccinated cohort of mothers influenced outcomes. Other studies will be needed to confirm these findings.
That said, these data are actionable and urgently so. Maternal vaccination rates were woefully low in this dataset (16% of mothers to infants hospitalized for Covid-19 were vaccinated, compared to 32% among the comparison group).
Pregnancy and unvaccinated Covid-19 are a very dangerous combination. Maternal morbidity and mortality and rates of stillbirth are far higher among unvaccinated than normal. This means that women who are pregnant, or who might soon become pregnant, urgently need vaccination without delay. To be clear, the new CDC study does not imply that women should wait until pregnancy to get vaccinated. It does, however, imply that vaccinating during pregnancy among the previously unvaccinated has important benefits. That said, this study does indeed have implications on when the optimal time for pregnant women to boost might be. I’ll write on that soon, as promised.
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