A health worker doses the Pfizer-BioNtech COVID-19 coronavirus vaccine to a pregnant woman on January 23, 2021 at Clalit Health Services in the Israeli Mediterranean coastal city of Tel Aviv.

Jack Guez | AFP | Getty Images

The Centers for Disease Control and Prevention recommend Covid-19 shots for pregnant women after preliminary data from the largest study of coronavirus vaccine use in expectant mothers showed that Pfizer and Moderna shocks were effective for both women and men are safe for their babies.

The researchers did not find “obvious safety signals” in any of the 35,691 women followed in the peer-reviewed study published Wednesday by the New England Journal of Medicine. The data used in the study were self-reported and the ages of the participants ranged from 16 to 54 years.

“No safety concerns for third trimester vaccinees or safety concerns for their babies were observed,” said CDC Director Dr. Rochelle Walensky on Friday. “Therefore, CDC recommends pregnant people to receive Covid-19 vaccines.”

Researchers used the V-Safe Post-Vaccination Health Checker monitoring system, the V-Safe Pregnancy Register, and the Vaccine Adverse Event Reporting System to characterize the initial safety of mRNA Covid-19 vaccines in pregnant women.

Pregnant women were more likely to report injection site pain than those who weren’t, but fewer other side effects such as headache, myalgia, chills, and fever. Of the 827 participants who completed their pregnancies, the miscarriage rates were the same as before the pandemic.

The results are preliminary and only cover the first 11 weeks of the US vaccine rollout from December 14th to February 28th.

Pregnant women are more likely to be hospitalized and have a higher risk of death if they become infected with Covid-19. According to CDC data, vaccination is particularly important for this population group. Pharmaceutical companies have not included pregnant women in early efficacy and safety studies, but recent studies suggest that the vaccines are safe for them.

The researchers said “more longitudinal research, including tracking large numbers of women who were vaccinated earlier in pregnancy, is needed to inform mother, pregnancy and child results.”