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Kachikis A, Englund JA, Singleton M, Covelli I, Drake AL, Eckert LO. Short-term Reactions Among Pregnant and Lactating Individuals in the First Wave of the COVID-19 Vaccine Rollout. JAMA Netw Open. 2021;4(8):e2121310. doi:10.1001/jamanetworkopen.2021.21310
Vaccines against SARS-CoV-2 are highly effective in preventing COVID-19 illness.1,2 Research has found that COVID-19 is associated with adverse events in pregnancy,3 and recommendations therefore include offering SARS-CoV-2 vaccines to pregnant and lactating individuals, despite their lack of inclusion in initial clinical trials.4,5 To date, limited data on vaccine and pregnancy outcomes exist for SARS-CoV-2 vaccines in pregnancy and lactation.6 The objective of this study was to investigate experiences of pregnant and lactating individuals after receiving COVID-19 vaccines.
In January 2021, we launched an online prospective cohort study of adults primarily located in the United States who were pregnant, lactating, or planning pregnancy at the time of COVID-19 vaccination. This study was determined to be exempt from institutional review board review by the University of Washington (UW) Human Subjects Division (Common Rule category 2). We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. Individuals who were recruited and enrolled online in the UW COVID-19 Vaccine in Pregnancy and Lactation Registry using chain-referral and snowball sampling were invited to participate. Electronic written informed consent was obtained, and self-reported demographic (including race and ethnicity), pregnancy, vaccination perception, and outcome data, including report of day 1 vaccine reactions, were entered via surveys into Research Electronic Data Capture (REDCap) software version 11.1.2 2021 (Vanderbilt University). Race and ethnicity data were collected to report diversity representation within our study population. Options for race and ethnicity were outlined following the Centers for Disease Control and Prevention’s National Health Interview Survey race and ethnicity categories. We performed statistical analysis (ie, χ2 tests and 1-way analysis of variance, odds ratios [ORs], and 95% CIs) using Stata statistical software version 16.1 (StataCorp). An α level of P ≤ .05, 2-sided, denoted significance. Data were analyzed from January through March 2021.
As of March 16, 2021, 17 525 individuals (17 364 [99.7%] women among 17 418 individuals with sex data; mean [SD] age, 33.6 [3.6] years among 17 518 individuals with age data; 15 361 White individuals [87.6%] among all individuals) with known pregnancy status receiving at least 1 dose of a COVID-19 vaccine had enrolled in the study. Owing to missing data, percentages for participant characteristics are among those with data for that variable. There were 3 distinct groups: 7809 individuals who were pregnant (44.6%), 6815 individuals who were lactating (38.7%), and 2901 individuals who were neither pregnant nor lactating but planning pregnancy in the near future (16.5%) at the time of their first vaccine dose. Most individuals received the Pfizer-BioNTech BNT162b2 vaccine (10 790 of 17 431 individuals [61.9%] with data on vaccine type) or Moderna mRNA-1273 vaccine (6592 individuals [37.8%]). Most participants resided in the United States, were employed in health care, and had completed some college education (Table). Among all participants, 15 055 individuals (85.9%) reported receiving 2 doses.
Among all participants, 17 005 individuals (97.0%) reported any postvaccination reactions after the first dose, with the most common reactions being pain at injection site (16 019 individuals [91.4%]) and fatigue (5489 individuals [31.3%]). The frequency of reactions after the second dose was higher than after the first dose (eg, 10 399 individuals [69.2%] with fatigue after the second dose), but with similar distribution of symptoms (Figure). Odds of several reactions were statistically significantly decreased among individuals who were pregnant (eg, fever after BNT162b2 dose 2: OR, 0.44; 95% CI, 0.38-0.52; P < .001 and after mRNA-1273 dose 2: OR, 0.48; 95% CI, 0.40-0.57; P < .001) compared with individuals who were neither pregnant nor lactating (Figure). Mean (SD) maximum self-reported temperature was 38.1 (0.6) °C (100.6 [1.0] °F) among 499 participants with fever after dose 1 (including 131 pregnant individuals) and 38.2 (0.6) °C (100.7 [1.0] °F) among 3293 participants with fever after dose 2 (including 1051 pregnant individuals). Participants seeking medical care after vaccination included 100 individuals (0.6%) after dose 1 (including 50 pregnant individuals) and 221 individuals (1.5%) after dose 2 (including 156 pregnant individuals).
Among pregnant participants, any obstetrical symptoms were reported by 346 of 7809 individuals (4.4%) after the first dose and 484 of 6444 individuals (7.5%) after the second dose. Altogether, 6586 pregnant individuals (84.3%) had reported a second vaccine dose at the time of data analysis. Of these, 6244 individuals (94.8%) were still pregnant, while 288 individuals (4.3%) had delivered and 49 individuals (0.7%) reported miscarriages at the time of their second vaccine dose. Among lactating individuals, interrupted breastfeeding after vaccination was reported by 155 of 6815 individuals after the first dose (2.3%) and 130 of 6056 individuals after the second dose (2.2%), decreased milk supply for less than 24 hours by 339 individuals after the first dose (5.0%) and 434 individuals after the second dose (7.2%), and concerns about the infant after vaccination by 208 individuals after the first dose (3.0%) and 267 individuals after the second dose (4.4%).
This large prospective cohort study found that COVID-19 vaccines were well-tolerated among individuals who were pregnant, lactating, or planning pregnancy. A strength of this study was the ability to compare vaccine reactions and perceptions in pregnant and lactating individuals vs individuals of similar age and fertility intentions who were neither pregnant nor lactating. Vaccination reactions for day 1 were similar among groups and comparable with findings among pregnant individuals previously reported.6 All groups reported increased reactions following dose 2 of BNT162b2 and mRNA-1273 vaccines.
Study limitations include that participants were drawn from a convenience sample with self-reported reactions and with limited perinatal outcome assessment, reflecting the first wave of vaccination, which largely consisted of health care workers owing to vaccine eligibility at the time of this ongoing study. As a result, our findings may be biased and not generalizable to all populations. In addition, there is potential participant overlap between our study and similar studies.6 Further studies are ongoing to investigate outcomes after receipt of COVID-19 vaccines among pregnant and lactating individuals.
Accepted for Publication: June 11, 2021.
Published: August 17, 2021. doi:10.1001/jamanetworkopen.2021.21310
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Kachikis A et al. JAMA Network Open.
Corresponding Author: Alisa Kachikis, MD, MS, Department of Obstetrics and Gynecology, University of Washington, 1959 NE Pacific St, Box 356460, Seattle, WA 98195 (firstname.lastname@example.org).
Author Contributions: Drs Kachikis and Singleton had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Kachikis, Eckert.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Kachikis, Englund, Drake.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Kachikis, Singleton, Drake.
Obtained funding: Kachikis.
Administrative, technical, or material support: Kachikis, Englund, Covelli, Drake, Eckert.
Supervision: Kachikis, Eckert.
Conflict of Interest Disclosures: Drs. Kachikis, Drake, and Englund reported receiving grants from Merck outside the submitted work. Dr Kachikis reported serving as a research consultant for Pfizer and GlaxoSmithKline on maternal immunization–related projects in 2020 outside the submitted work. Dr Englund reported receiving consulting fees from Sanofi Pasteur, Meissa Vaccines, and AstraZeneca and grants from Pfizer, GlaxoSmithKline, AstraZeneca, Novavax, and Chimerix outside the submitted work. No other disclosures were reported.
Funding/Support: This project was supported by Women’s Reproductive Health Research grant K12HD001264-21 through the National Institute of Child Health and Human Development, grant K23AI153390-01A1 through the National Institute of Allergy and Infectious Diseases, and grant UL1 TR002319 from the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health for the purposes of design and conduct of the study and collection, management, analysis, and interpretation of data. The UW Institute of Translational Health Science provided administrative Research Electronic Data Capture support for this project and was supported by grants UL1 TR002319, KL2 TR002317, and TL1 TR002318 from NCATS.
Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Additional Contributions: We would like to acknowledge foremost the individuals who contributed their valuable time to this study.
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