Lactation education

COVID-19 vaccine boosters are well tolerated during pregnancy and lactation

September 12, 2022

2 minute read


Disclosures: Kachikis reports that he served as a research consultant for Pfizer and GlaxoSmithKline on projects related to maternal immunization in 2020, served as an unpaid consultant for GlaxoSmithKline in 2022 outside of the study, and received a grant from Merck and Pfizer outside the study. Please see the study for relevant financial information from all other authors.


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

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




Data derived from Kachikis A, et al. JAMA Netw Open. 2022; doi:10.1001/jamanetworkopen.2022.30495.

The results come from an ongoing study, which began in January 2021, of adults who are pregnant, breastfeeding and/or planning a pregnancy. For the current study, Kachikis and her 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

Of 17,504 people eligible to participate on 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-related concerns and to breastfeeding. Of these, 2,009 (11.8%) participants were pregnant, 10,279 (60.4%) were breastfeeding, and 4,726 (27.8%) were neither pregnant nor breastfeeding at the time they received their booster or their third dose.

The Pfizer-BioNTech vaccine was the most common type of vaccine among 16,989 participants who reported the vaccine they had received (n=10,319; 60.7%). The largest 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%) quarters.

Vaccine reactions

Overall, 15,674 (92.2%) of 17,005 respondents reported vaccine reactions, of which 14,074 (82.8%) reported local reactions and 11,542 (67.9%) reported vaccine reactions. 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 a local reaction than those who were not pregnant or breastfeeding when they received their dose (adjusted OR = 1.2; 95% CI, 1-1.4). However, they were less likely to report a systemic reaction compared to non-pregnant, non-breastfeeding respondents (aOR = 0.7; 95% CI, 0.6-0.8).

The most common pregnancy-related problem within 24 hours of receiving a booster or third dose was contractions, which occurred in 11 (0.6%) of 2,009 pregnant women surveyed, who were all in their third trimester. Of 10,278 respondents who were breastfeeding, only 83 (0.8%) experienced an increase in breastmilk production, 355 (3.5%) a decrease in production and 121 (1.2%) reported problems with their breastfed infant after vaccination.

Vaccine hesitancy

Of note, pregnant participants reported more hesitancy to receive the booster or third dose of the vaccine compared to non-pregnant, non-lactating participants (aOR = 2.3; 95% CI, 2-2.7). Despite this, they were also more likely to report that they had discussed the booster dose with a healthcare professional (aOR = 25.8; 95% CI, 22.3-29.8) and that recommended they receive it (aOR = 6.8; 95% CI , 5.8-8) compared to their non-pregnant, non-breastfeeding counterparts.

“COVID-19 vaccine recall data is particularly important because vaccination during pregnancy is lagging behindand strategies to reduce vaccine hesitancy, increase vaccine acceptance, and help guide discussions between pregnant and breastfeeding women and maternal care professionals are needed,” Kachikis and colleagues wrote.