New Study Supports Safety of COVID-19 Boosters During Pregnancy

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Women who are pregnant or breastfeeding showed no long-term adverse reactions after a third or booster dose of COVID-19 vaccine, according to a study of more than 17,000 individuals.

Doctors and health professionals continue to recommend COVID-19 vaccine boosters or third doses for adolescents and adults more than 5 months after their initial vaccinations with the Pfizer-BioNTech BNT162b2 or Moderna mRNA-1273 primary vaccine series or more than 2 months after receiving the Janssen JNJ-78436735 vaccine, Alisa Kachikis, MD, of the University of Washington, Seattle, and colleagues wrote in JAMA Network Open.

Although multiple studies have shown that the COVID-19 primary series is safe and well tolerated in pregnant and lactating women, information on the safety and tolerability of boosters are lacking, the researchers noted.

“COVID-19 will be with us for a while, and it is important to continue to provide data on COVID-19 vaccines in these groups, particularly because there still are many questions about the vaccine, and because pregnant individuals have been, understandably, more hesitant to receive COVID-19 vaccines,” Kachikis said in an interview. “The findings of this study that COVID-19 booster doses are well tolerated among pregnant and lactating individuals are especially pertinent with the new COVID-19 boosters available this fall.”

In the new study, the researchers reviewed data from 17,014 participants who were part of an ongoing online prospective study of COVID-19 vaccines in pregnant and lactating individuals. Data were collected between October 2021 and April 2022 through an online survey.

The study population included 2,009 participants (11.8%) who were pregnant at the time of their booster or third dose, 10,279 (60.4%) who were lactating, and 4,726 (27.8%) who were neither pregnant nor lactating. The mean age of the participants was 33.3 years; 92.1% self-identified as White, 94.5% self-identified as non-Hispanic, and 99.7% self-identified as female.

The receipt of a booster was similar across trimesters; 26.4%, 36.5%, and 37.1% of participants received boosters or third doses in the first, second, and third trimester, respectively. The primary outcome was self-reported vaccine reactions within 24 hours of the dose.

Overall, 82.8% of the respondents reported a reaction at the site of the injection, such as redness, pain, or swelling, and 67.9% reported at least one systemic symptom, such as aches and pains, headache, chills, or fever. The most frequently reported symptoms across all groups were injection-site pain (82.2%) and fatigue (54.4%).

The pregnant women were significantly more likely than nonpregnant or nonlactating individuals to report any local reaction at the injection site (adjusted odds ratio, 1.2; P = .01), but less likely to report any systemic reaction (aOR, 0.7; P < .001).

The majority (97.6%) of the pregnant respondents and 96.0% of those lactating reported no obstetric or lactation concerns after vaccination.

Overall, a majority of the respondents reported that recommendations from public health authorities were helpful in their decision to receive a COVID-19 booster or third dose (90.0% of pregnant respondents, 89.9% of lactating respondents, and 88.1% of those neither pregnant nor lactating).

Although vaccine uptake in the current study population was high (91.1% overall and 95.0% of those pregnant), “the importance of the health care professional’s recommendation is pertinent given the ongoing increased vaccine hesitancy among pregnant individuals in the context of the COVID-19 vaccine,” the researchers emphasized.

The study findings were limited by several factors including the reliance on self-reports and a convenience sample composed mainly of health care workers because of their vaccine eligibility at the time the study started, which limits generalizability, the researchers noted. Analyses on the pregnancy outcomes of those who were pregnant when vaccinated are in progress.

The results were strengthened by the large study population that included participants from all 50 states and several territories, and ability to compare results between pregnant and lactating individuals with those who were neither pregnant nor lactating, but were of childbearing age, they said.

The results support the safety of COVID-19 boosters for pregnant and breastfeeding individuals, and these data are important to inform discussions between patients and clinicians to boost vaccine uptake and acceptance in this population, they concluded.

“Our earlier data analysis showed that pregnant and lactating individuals did very well with the initial COVID-19 vaccine series, so it was not very surprising that they also did well with COVID-19 booster or third doses,” Kachikis said in an interview.

There are two takeaway messages for clinicians, she said: “First, pregnant and lactating individuals tolerated the COVID-19 booster well. The second is that clinicians are very important when it comes to vaccine acceptance.”

“In our study, we found that, while pregnant participants were more likely to report that they were hesitant to receive the booster, they also were more likely to have discussed the COVID-19 booster with their health care provider, and to have received a recommendation to receive the booster. So, spending a little bit of extra time with patients discussing COVID-19 boosters and recommending them can make a significant difference,” she said.

The message of the study is highly reassuring for pregnant and lactating individuals, Kachikis added. “Most of the participants reported that they had fewer symptoms with the COVID-19 booster compared to the primary vaccine series, which is good news, especially since a new COVID-19 booster is being recommended for the fall.”

Reassuring Findings for Doctors and Patients

The current study is especially timely, as updated COVID-19 boosters have now been recommended for most individuals by the Centers for Disease Control and Prevention, Martina L. Badell, MD, a maternal-fetal medicine specialist at Emory University, Atlanta, said in an interview.

The findings support previous studies on the tolerability of COVID-19 vaccinations in pregnant and lactating persons, said Badell, who was not involved in the study.

The reassuring message for clinicians is that COVID-19 booster vaccinations are similarly well tolerated in pregnancy and lactation as they are in nonpregnant individuals, said Badell. “Given the risks of COVID infections in pregnancy and neonates, reassuring data on the tolerability and safety of vaccination in this population is very important.” Also, the researchers found that all three cohorts reported that recommendations from public or medical health authorities helped them make a decision about vaccination; “thus the more data to support these recommendations, the better,” she emphasized.

If you are pregnant or breastfeeding, the message from the study is that COVID-19 booster vaccinations are similarly well tolerated by those who are pregnant or breastfeeding and those who are not, said Badell.

“This study provides additional support for the strong recommendation to encourage not only COVID-19 vaccination in pregnancy and lactation, but booster vaccinations specifically,” and pregnant and breastfeeding individuals should not be excluded from the new CDC recommendations for COVID-19 boosters, she said.

Future Research Suggestions

Next steps for research include evaluating the obstetrical and neonatal outcomes in pregnancy and lactation following COVID- 19 boosters, Badell added.

Kachikis suggested studies try to answer the remaining questions about COVID-19 vaccines and the immunity of pregnant and lactating persons, particularly since they were excluded from the early clinical trials in 2020.

The study was supported by the National Institute of Allergy and Infectious Diseases, a Women’s Reproductive Health Research Award, and the National Center for Advancing Translational Sciences of the National Institutes of Health. \Kachikis disclosed serving as a research consultant for Pfizer and GlaxoSmithKline and as an unpaid consultant for GlaxoSmithKline unrelated to the current study, as well as grant support from Merck and Pfizer unrelated to the current study. Badell had no financial conflicts to disclose.

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