Pfizer And Moderna Vaccines Not Linked To Birth Defects, Study Finds

 

The study adds to data supporting the safety and effectiveness of Covid vaccines during pregnancy.

There is no evidence of major birth defects in babies born to mothers vaccinated against COVID-19 during the first trimester of pregnancy, according to new research published in JAMA Pediatrics on Monday, underscoring the safety of vaccination during pregnancy amid mounting evidence of the severe health risks infections can cause for mothers and babies.

KEY FACTS

Exposure to Pfizer and Moderna’s mRNA Covid vaccines during the first trimester of pregnancy was “not associated with an increased risk” of major birth defects including problems with the eyes, ears, neural tube, kidneys, respiratory system and musculoskeletal system, according to a team of researchers from across the U.S.

The findings come from an analysis of healthcare data covering more than 42,000 pregnancies linked to live births between early March 2021 and late January 2022 that were registered in the Vaccine Safety Datalink database from eight healthcare systems in California, Oregon, Washington, Colorado, Minnesota, and Wisconsin.

Nearly a fifth of the pregnant people, around 7,600, received a dose of an mRNA Covid vaccine during the first trimester — one of the most vulnerable periods of pregnancy for harmful exposures and birth defects — the researchers said, with 19,000 not receiving a vaccine before or during pregnancy and 13,500 getting a dose in their second or third trimesters but not in their first.

The dose was the second vaccine for around 1,350 of the pregnant people vaccinated in their first trimester, the researchers said, with around 46% of the group going on to get their second dose during the second or third trimesters and 20% getting a third booster dose.

The researchers said their findings indicate no increased risk for major structural birth defects following first-trimester vaccination, adding this is in line with the handful of other studies from Scotland and Israel to comprehensively assess the association between maternal vaccination and birth defects in infants.

The findings, which only cover Pfizer and Moderna’s COVID-19 vaccines, “should provide reassurance to pregnant people and their obstetric care practitioners,” the researchers said.

KEY BACKGROUND

Researchers and officials are naturally very cautious about giving newly approved healthcare products to pregnant people due to the risks for parent and child. This is especially true early on in pregnancy, when the risks of exposure to potential hazards is higher and for newer technology, like mRNA vaccines, that have been less widely studied in the population compared to more established products, and drugmakers routinely exclude pregnant people from trials over safety concerns. This caution was on full display during the early stages of vaccine rollout during the COVID-19 pandemic, when the shots were new and less was known about the virus and risks it posed to pregnant people and infants. There was little to no data about vaccination in pregnant people then and both experts and leading health agencies around the world, including the World Health Organization, were divided over how to proceed, sometimes discouraging and sometimes encouraging pregnant people from getting vaccinated. Experts and top health authorities now widely encourage pregnant people to get vaccinated without delay and there is an increasing array of evidence highlighting the serious health risks to mother and baby from Covid infections, including respiratory issues, preterm birth, stillbirth and neurological and developmental issues. Research also suggests maternal vaccination can protect the baby in the first six months of life after birth.

TANGENT

The Centers for Disease Control and Prevention recommends vaccination at any point in pregnancy and says studies from around the world involving hundreds of thousands of people show vaccination both before and during pregnancy is safe and effective and beneficial to “both the pregnant person and the baby.” mRNA vaccines reduce the risk of severe illness and other health effects from COVID-19 during pregnancy, the CDC said, as well as helping to build protective antibodies that can protect the baby. The agency stresses “the benefits of receiving a COVID-19 vaccine outweigh any potential risks of vaccination during pregnancy.”

WHAT WE DON’T KNOW

Data on side effects, especially rare ones, can take a while to emerge and it is hard to capture on relatively small sample sizes like pregnant people. The researchers said their findings only considered single births, as well as pregnancies ending in live birth, which would naturally exclude any defects resulting in stillbirth or similar outcome, as this data was not captured in the database available. Some other issues can take time to emerge, the researchers acknowledged, and though they were only able to evaluate defects up to four months from birth they said this time frame has proven to have a solid predictive value in the past.