Vaccination against Covid in pregnancy protects babies against infection and hospital admission
The findings suggest that vaccination during pregnancy may have benefits for both mother and baby.
Two doses of the mRNA Covid-19 vaccine during pregnancy are highly effective against Delta infection and moderately effective against Omicron infection, and are linked to a lower risk of hospital admission in infants younger than six months, according to a published Canadian study. today by The BMJ.
Protection against Omicron infection was greatest when the mother received a second dose of vaccine in late pregnancy and was also greatest for infants in their first eight weeks of life. Receiving a third (booster) dose during pregnancy also strengthened protection against Omicron.
Although most cases of Covid-19 in infants are mild, rates of hospitalization and severe illness have been higher in infants compared to older children, especially during the first month of life or when the infection is complicated by other conditions. .
Covid vaccines are not yet licensed for babies under six months, but emerging evidence suggests that vaccination during pregnancy may reduce the risk of infection and hospitalization in babies, as antibodies are transferred across the placenta and breast milk (a process known as passive immunity).
To shed more light on this, researchers in Canada set out to estimate the effectiveness of maternal Covid-19 mRNA vaccination during pregnancy against Delta and Omicron infection and hospitalization in infants.
The study involved infants under the age of six months who were born in Ontario between May 7, 2021 and March 31, 2022 and who underwent a PCR test for Covid-19 infection between May 7, 2021 and September 5, 2022.
This information was then linked to data on maternal Covid-19 mRNA vaccination during pregnancy (one, two or three doses) or unvaccinated (no doses), and recorded hospital admissions related to Delta and Omicron in babies.
A variety of potentially influential factors were taken into account, including the mother’s age at delivery, the number of previous pregnancies, pre-pregnancy conditions such as diabetes, heart disease and asthma, and the baby’s sex.
In total, they included 8809 babies in the main analysis (99 positive Delta cases compared to 4365 negative controls and 1501 Omicron cases compared to 4847 controls).
Results show that two doses of vaccine during pregnancy were 95% effective against Delta infection in infants and 97% effective against infant Delta hospitalization.
The efficacy of two doses against Omicron infection in infants (45%) and hospital admission (53%) was moderate, but was improved by a third dose during pregnancy (73% and 80%, respectively).
