Jab during pregnancy cuts baby's Covid-19 risk, study says.

When expectant mothers are vaccinated for Covid-19 during pregnancy, their babies get protection from the virus after birth, new data has revealed.

Babies whose mothers received two shots of either the Pfizer or Moderna vaccine during pregnancy had a 61 per cent lower risk of being hospitalised with Covid-19 in their first six months of life, the study shows.

The study, published by the US Centers for Disease Control and Prevention (CDC), also showed that the protection appeared to be higher among infants whose mothers were vaccinated later in pregnancy.

"Most concerning, they found that among babies with Covid-19, who were admitted to the ICU, the sickest babies, 88 per cent, were born to mothers who were not vaccinated before or during pregnancy, and the one baby who died in the study was born to a mother who was not vaccinated," said Dr Dana Meaney-Delman, chief of the CDC's infant outcomes monitoring research and prevention branch.

"For other diseases like flu and whooping cough, vaccination during pregnancy provides protection for infants during the first six months of their lives, a period when infants are at high risk for severe illness, but when they are not yet old enough to get vaccinated."

The CDC recommends Covid-19 vaccination for pregnant women as they are at high risk for complications if they are infected during pregnancy.

The researchers examined data on 379 infants hospitalised for various reasons, including Covid-19, across 17 states from July 1, 2021 to January 17, 2022.

According to the findings, Covid-19 antibodies could be transferred across the placenta from a mother to the baby during pregnancy and "might provide protection to infants".

"When people receive an mRNA Covid-19 vaccine during pregnancy, their bodies build antibodies to protect against Covid-19 and these antibodies have been found in umbilical cord blood, indicating that the antibodies had transferred from the pregnant person to the developing infant," Dr Meaney-Delman added.

In November, the American College of Obstetricians and Gynaecologists also recommended boosters for all eligible pregnant people.

The new study did not include data on the vaccine effectiveness of booster shots or on mothers who were vaccinated before pregnancy.

Study co-author Dr Manish Patel said the researchers aim to look at the effect of boosters in the future.

"I think it's fair to say from all of the evidence on boosters increasing protection and antibody levels that we should see higher protection, definitely not lower protection with boosters."