Pfizer and Moderna Vaccines Appear Safe, Effective During Pregnancy

Jaleesa Baulkman

April 28, 2021

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The Pfizer and Moderna COVID-19 vaccines appear to be safe in pregnant patients, according to preliminary findings published in the New England Journal of Medicine.

The Centers for Disease Control and Prevention have said pregnant people have an increased risk of being severely ill from COVID-19; however, this group was excluded from major clinical trials that led up to the current vaccine approvals.

But based on the new findings, Rochelle Walensky, MD, director of the CDC, announced during a White House COVID-19 briefing that the CDC recommends that pregnant people receive the COVID-19 vaccine.

The new study, which analyzed data between Dec. 14, 2020, and Feb. 28, 2021, from three federal databases, adds to a pool of limited data about the safety and efficacy of the vaccine in pregnant persons. Researchers did not include people who received the Johnson & Johnson vaccine because it received emergency use authorization on Feb. 27, just 1 day before they study's cutoff.

"Our hope is that these initial data will be reassuring to pregnant people and their health care providers as well as the public, and contribute to increasing vaccination rates," study author Christine Olson, MD, said in an interview. "While the data are preliminary and will continue to be analyzed as more reports become available, our findings are reassuring."

For the study, Olson and colleagues analyzed v-safe survey data, data from those enrolled in the v-safe pregnancy registry, and Vaccine Adverse Event Reporting System (VAERS) reports.

Researchers found that 86% of pregnancies resulted in a live birth, 12.6 % resulted in spontaneous abortions, and 0.1% resulted in stillbirth. They also found that, among the live births, 9.4% were preterm, 3.2% of babies were small for their gestational age, and 2.2% had congenital anomalies.

Researchers also found that injection-site pain, fatigue, and headaches were reported more frequently in pregnant patients than among those who were not pregnant. Among VAERS reports, they found that 70% of adverse events were nonpregnancy specific. Nearly 30% involved pregnancy- or neonatal-specific adverse events. The most frequently reported pregnancy-related events were spontaneous abortions, followed by stillbirths, premature rupture of membranes and vaginal bleeding.

"I think the results are actually quite reassuring as the proportion of the pregnancy outcomes, such as pregnancy loss and health effects to the newborns, are really quite consistent with what we'd expect in the background rate of the population," Walensky said in a podcast accompanying the study. "So this study adds to growing evidence confirming that pregnant people develop a robust immune response to COVID-19 vaccination without so far seeing any adverse events to the mom or the fetus."

Researchers said limitations of the study include the accuracy of self-reported data, and there being limited information on other potential risk factors for adverse pregnancies and neonatal outcomes. They acknowledged that continuous monitoring is needed to look at maternal safety and pregnancy outcomes in earlier stages of pregnancy and during the preconception period.

David Jaspan, DO, chair of the department of obstetrics and gynecology at Einstein Medical Center, Philadelphia, who was not involved with the study, said in an interview that, despite the limitations, the study provides much-needed insight on the vaccine's safety and efficacy in pregnant patients.

"In December we had no data for any pregnant patient," Jaspan said. "And now just 4 short months later, this paper [has data from] at least had 35,000 people. We can't answer every question, but we have more answers today than we had just 4 months ago."

Olson hopes the present data is enough to help inform decision-making of pregnant patients and their health care providers when it comes to deciding to get the COVID-19 vaccination.

The study author and experts interviewed disclosed no relevant financial relationships.

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