Maternal vaccination and protection to infants under vaccination age.

Here is a recent NEJM study on the protection of maternal vaccination and risk of coronavirus hospitalization for infants (<6 months of age). This age group can't be vaccinated against coronavirus, but we have a body of evidence now that they get protection if their mother was vaccinated before they were born. This further stresses the importance of pregnant women getting vaccinated as it not only protects the mother and reduces the risk of pregnancy complications, but also provides protection to the newborn.

Vaccination during pregnancy provided a vaccine effectiveness against hospitalization to newborns of 80% (95% CI of 60-90) during Delta and 38% (95% CI of 8-58) during Omicron. Protection against ICU admission was 70% (95% CI of 42-85). Point estimates were higher if the second dose occurred after 20 weeks of pregnancy.

Healthy mother bias can't be completely excluded, but results are consistent with vaccination providing protection as vaccination effectiveness was higher during Delta and higher against ICU admission. While not significant, point estimates were higher if the second dose occurred after 20 weeks, which is consistent with other vaccine data suggesting stronger vaccine protection if it occurs during the second and third trimesters.

We also have past research that indicates newborns receive antibodies through the cord blood, and that these antibody levels are higher among infants born to vaccinated mothers than mothers with previous coronavirus infection. And for other vaccines like the pertussis vaccine, we see that maternal vaccination provides benefit to newborns.

Unfortunately the vaccination rates of pregnant mothers are quite low, especially among Black and Hispanic women. Pregnancy increases the risk of severe COVID, and coronavirus infection can lead to birth complications and premature birth. And vaccination provides better protection than previous coronavirus infection for both the mother and newborn. The vaccines are safe during pregnancy.

And they couldn't evaluate prior coronavirus infection, which may have reduced the observed vaccination effectiveness from the true vaccination effectiveness.
Nor did they evaluate J&J or booster doses.