US Pharm. 2021;46(9):4.

A survey of more than 17,000 pregnant and lactating women who received the COVID-19 vaccine showed that the individuals did not experience symptoms any more severe than their nonpregnant counterparts.

The University of Washington (UW) Medicine study, published on August 17, 2021, in JAMA Network Open, showed “there were not any increased reactions in pregnant individuals beyond what is expected from a vaccine,” said Dr. Linda Eckert, a professor of obstetrics and gynecology at the UW School of Medicine and the study’s senior author. “Pregnant people do well with the vaccine,” added lead author Dr. Alisa Kachikis. The findings come a week after the CDC formally recommended that all pregnant women get vaccinated against the virus.

In January 2021, Dr. Kachikis set up an online cohort study of women: those who were pregnant or lactating and those who were neither pregnant nor lactating. The women were invited to describe their reactions after receiving at least one dose of a COVID-19 vaccine. By March, 17,525 individuals had responded. The respondents comprised women who were pregnant (44%) or lactating (38%) and those who stated plans to become pregnant in the near future (15%).

The majority (62%) received the Pfizer vaccine, and most of the participants resided in the United States. Respondents reported pain at the injection site (91%) and fatigue (31%), and a mean temperature of 100°F after the shot. A small group (5%-7%) reported a decrease in milk supply postvaccination.

The study found that women tolerate the vaccine well, supporting that they should be included in clinical trials for other relevant vaccines, Dr. Eckert said. “I’m not surprised but I am pleased by the outcome. It’s further evidence that the vaccine is safe and well tolerated in pregnant individuals.”

There are currently 20,000 women enrolled in the study, and new respondents continue to post their experiences, Dr. Kachikis added. The researchers hope to expand the study to other socioeconomic groups and to women not so closely tied to healthcare, as this group was, Dr. Eckert said. “I think this gives a level of evidence to advocate for phase III trials (for pregnant individuals) in the future,” she added.

The timing of the positive findings related to the COVID-19 vaccine in pregnant women is fortuitous: Based on data from the CDC’s Vaccine Safety Datalink, as of August 21, about three in four pregnant women aged 18 to 49 years were unvaccinated. In addition, a recent study from the University of California Irvine Health revealed that expectant mothers with COVID-19 were 40% more likely to deliver prematurely. That study also found that pregnant women had higher rates of ICU admissions, intubation, and mortality.