The findings shed light on whether the benefits of vaccination during pregnancy extend to infants who would be too young to receive COVID vaccines.
Vaccinating pregnant women against COVID-19 may help prevent hospitalisations from the virus in infants after they are born, especially if the expectant mothers got the shots later in their pregnancy, new research released on Tuesday suggests.
The findings shed light on whether the benefits of vaccination during pregnancy extend to infants who would be too young to receive vaccines.
Researchers from several American pediatric hospitals and the US Centers for Disease Control and Prevention (CDC) looked at children under six months old between July 2021 and January 2022.
The study analysed data from 379 hospitalised infants; 176 with COVID-19 and 203 who were admitted for other issues.
It found that COVID-19 vaccines were 61 per cent effective overall at preventing hospitalisations in children whose mothers were vaccinated during pregnancy.
That protection rose to 80 per cent when the mothers were vaccinated 21 weeks through 14 days before delivery.
Vaccination effectiveness fell to 32 per cent for the babies whose mothers were inoculated earlier during pregnancy.
COVID complications during pregnancy
The study authors warned that the estimates for effectiveness earlier in pregnancy should be interpreted with caution due to the small sample size.
"Right now we want to ensure that we are protecting both the mom and the infant," CDC's Dana Meaney-Delman said.
"So as soon as a pregnant woman is willing to be vaccinated, she should so ahead and do so".
Pregnant women are at increased risk for severe illness from COVID-19, and being infected by the virus during pregnancy can increase the risk of preterm birth, stillbirth and possibly other pregnancy complications, according to the CDC.
The CDC recommends that women who are pregnant, are breastfeeding, are trying to get pregnant now, or might become pregnant in the future get vaccinated and stay up to date with COVID-19 shots.
In January, the European Medicines Agency (EMA) also encouraged pregnant women to get vaccinated, pointing out the mounting evidence that suggests mRNA vaccines like those produced to combat the virus do not cause complications during pregnancy, including premature delivery and underweight babies.