More Evidence of the Safety of Monovalent COVID-19 Boosters During Pregnancy

Pharmacists have even more countervailing evidence for expectant mothers who express concerns about vaccination against COVID-19: The monovalent booster is not associated with spontaneous abortion. Allaying the fears of pregnant women is especially important because adherence to booster vaccines especially lags in that cohort. Here are more details.

BLOOMINGTON, MN – Pharmacists are often questioned about the safety of vaccination against COVID-19 in pregnant women.

New research from HealthPartners Institute should help allay those fears. A report in JAMA Network Opendemonstrates that monovalent COVID-19 booster vaccinations administered in early pregnancy, defined as before 20 weeks gestation, were not associated with miscarriage.

The new information is important because adherence to COVID-19 booster vaccine recommendations “has lagged in pregnant and nonpregnant adult populations,” according to the researchers, who add, “One barrier to booster vaccination is uncertainty regarding the safety of booster doses among pregnant people.”

The study team sought to evaluate whether there is an association between COVID-19 booster vaccination during pregnancy and spontaneous abortion.

The observational, case-control, surveillance study evaluated women aged 16 to 49 years with pregnancies at 6 to 19 weeks gestation at 8 health systems in the Vaccine Safety Datalink from Nov. 1, 2021, to June 12, 2022.

Defined as the primary exposure was receipt of a third messenger RNA (mRNA) COVID-19 vaccine dose within 28 days before spontaneous abortion or index date (midpoint of surveillance period in ongoing pregnancy controls). Third mRNA vaccine doses in a 42-day window or any COVID-19 booster in 28- and 42-day windows were considered secondary exposures.

The study team identified spontaneous abortion cases and ongoing pregnancy controls from electronic health data using a validated algorithm. With the 112,718 unique pregnancies included in the study, the mean (SD) maternal age was 30.6 (5.5) years. Expectant mothers were Asian, non-Hispanic (15.1%); Black, non-Hispanic (7.5%); Hispanic (35.6%); White, non-Hispanic (31.2%); and of other or unknown (10.6%).

Across eight 28-day surveillance periods, among 270 853 ongoing pregnancy-period controls, 11,095 (4.1%) had received a third mRNA COVID-19 vaccine in a 28-day window. The study also found that, among 14, 226 cases, 553 (3.9%) had received a third mRNA COVID-19 vaccine within 28 days of a spontaneous abortion.

“Receipt of a third mRNA COVID-19 vaccine was not associated with spontaneous abortion in a 28-day window (AOR, 0.94; 95% CI, 0.86-1.03),” the authors emphasize. “Results were consistent when using a 42-day window (AOR, 0.97; 95% CI, 0.90-1.05) and for any COVID-19 booster in a 28-day (AOR, 0.94; 95% CI, 0.86-1.02) or 42-day (AOR, 0.96; 95% CI, 0.89-1.04) exposure window.”

The authors write that their findings support the safety of recommendations for COVID-19 booster vaccination, including in pregnant women.

“COVID infection during pregnancy increases the risk of poor outcomes, yet many people who are pregnant or thinking about getting pregnant are hesitant to get a booster dose because of questions about safety. Our data supports the safety of booster vaccination in early pregnancy,” said lead author Elyse Kharbanda, MD, MPH, senior investigator at HealthPartners Institute.

Other HealthPartners Institute research recently published in Obstetrics & Gynecologyindicates that COVID-19 booster vaccination at any point during pregnancy was not associated with increased risk for serious acute adverse events.

The study including 80,000 pregnancies that occurred between Sept. 23, 2021, and June 30, 202, found that booster vaccination in pregnancy did not increase risks for thrombocytopenia, myocarditis, venous thromboembolism, ischemic stroke, or other serious adverse events within 21 or 42 days after vaccination.

“We continue to find that COVID-19 vaccinations in pregnancy are safe,” said lead author Malini DeSilva, MD, MPH, investigator at HealthPartners Institute. “Ongoing vaccine surveillance work is important because it provides reassurance and helps people feel confident in their vaccinations.”

The Vaccine Safety Datalink (VSD) is a research network funded by the national Centers for Disease Control and Prevention that conducts post-marketing surveillance of vaccines licensed and used in the United States.

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