COVID-19 vaccine boosters well-tolerated during pregnancy, lactation

People who were pregnant or lactating when they received a booster or third dose of the COVID-19 vaccine tolerated it well, according to the results of a prospective cohort study published in JAMA Network Open.

“Although studies have shown the COVID-19 primary vaccine series to be well-tolerated and safe for pregnant and lactating individuals, data are lacking on COVID-19 vaccine boosters or third doses among this population,” Alisa B. Kachikis, MD, MSc, an OB/GYN and attending in the division of maternal-fetal medicine at the University of Washington in Seattle, and colleagues wrote. “We investigated reactions to the COVID-19 vaccine booster doses and vaccine experiences among pregnant and lactating individuals.”

The results were from an ongoing study, which began in January 2021, of adults who are pregnant, lactating and/or planning a pregnancy. For the present study, Kachikis and colleagues began sending an online survey in October 2021 to participants who reported receiving a booster or third dose of the COVID-19 vaccine.

Cohort characteristics

Among 17,504 individuals eligible to participate as of April 4, 2022, 17,014 (97.2%) responded to the survey, which asked about local and systemic reactions to the vaccine, as well as pregnancy- and lactation-related concerns. Of these, 2,009 (11.8%) participants were pregnant, 10,279 (60.4%) were lactating and 4,726 (27.8%) were neither pregnant or lactating at the time they received their booster or third dose.

The Pfizer-BioNTech vaccine was the most common vaccine type among 16,989 participants who reported the vaccine they received (n = 10,319; 60.7%). The greatest proportion of pregnant participants received their booster or third dose during the third trimester (n = 745; 37.1%), followed by the second (n = 733; 36.5%) and first (n = 530; 26.4%) trimesters.

Vaccine reactions

Overall, 15,674 (92.2%) of 17,005 respondents reported any reactions to the vaccine, with 14,074 (82.8%) reporting local reactions and 11,542 (67.9%) reporting systemic reactions. Injection site pain (n = 13,972; 82.2%) and fatigue (n = 9,247; 54.4%) were the most commonly reported symptoms.

Participants who received their booster dose during pregnancy were more likely to have any local reaction compared with those who were not pregnant or lactating when they received their dose (adjusted OR = 1.2; 95% CI, 1-1.4). However, they were less likely to report any systemic reaction compared with nonpregnant, nonlactating respondents (aOR = 0.7; 95% CI, 0.6-0.8).

The most common pregnancy-related concern within 24 hours of receiving a booster or third dose was contractions, which occurred in 11 (0.6%) of 2,009 pregnant respondents, all of whom were in their third trimester. For 10,278 respondents who were lactating, only 83 (0.8%) experienced an increase in breast milk supply, 355 (3.5%) had a decreased supply and 121 (1.2%) reported any issues with their breastfed infant after vaccination.

Vaccine hesitancy

Of note, participants who were pregnant reported being more hesitant about receiving the vaccine booster or third dose compared with nonpregnant, nonlactating participants (aOR = 2.3; 95% CI, 2-2.7). Despite this, they were also more likely to report that they discussed the booster dose with a health care professional (aOR = 25.8; 95% CI, 22.3-29.8) and that they were recommended to receive it (aOR = 6.8; 95% CI, 5.8-8) compared with their nonpregnant, nonlactating counterparts.

“Data on COVID-19 vaccine boosters are particularly important as vaccine uptake during pregnancy is lagging, and strategies to reduce vaccine hesitancy, increase vaccine acceptance and help guide discussions between pregnant and lactating persons and maternal care professionals are needed,” Kachikis and colleagues wrote.