Maternal mRNA COVID-19 Vaccination During Pregnancy

Effectiveness of Maternal Vaccination With mRNA COVID-19 Vaccine During Pregnancy Against COVID-19–Associated Hospitalization in Infants Aged <6 Months

17 States, July 2021-January 2022

Natasha B. Halasa, MD; Samantha M. Olson, MPH; Mary A. Staat, MD; Margaret M. Newhams, MPH; Ashley M. Price, MPH; Julie A. Boom, MD; Leila C. Sahni, PhD; Melissa A. Cameron, MD; Pia S. Pannaraj, MD; Katherine E. Bline, MD; Samina S. Bhumbra, MD; Tamara T. Bradford, MD; Kathleen Chiotos, MD; Bria M. Coates, MD; Melissa L. Cullimore, MD; Natalie Z. Cvijanovich, MD; Heidi R. Flori, MD; Shira J. Gertz, MD; Sabrina M. Heidemann, MD; Charlotte V. Hobbs, MD; Janet R. Hume, MD; Katherine Irby, MD; Satoshi Kamidani, MD; Michele Kong, MD; Emily R. Levy, MD; Elizabeth H. Mack, MD; Aline B. Maddux, MD; Kelly N. Michelson, MD; Ryan A. Nofziger, MD; Jennifer E. Schuster, MD; Stephanie P. Schwartz, MD; Laura Smallcomb, MD; Keiko M. Tarquinio, MD; Tracie C. Walker, MD; Matt S. Zinter, MD; Suzanne M. Gilboa, PhD; Kara N. Polen, MPH; Angela P. Campbell, MD; Adrienne G. Randolph, MD; Manish M. Patel, MD

Disclosures

Morbidity and Mortality Weekly Report. 2022;71(7):264-270. 

In This Article

Abstract and Introduction

Introduction

COVID-19 vaccination is recommended for persons who are pregnant, breastfeeding, trying to get pregnant now, or who might become pregnant in the future, to protect them from COVID-19.§ Infants are at risk for life-threatening complications from COVID-19, including acute respiratory failure.[1] Evidence from other vaccine-preventable diseases suggests that maternal immunization can provide protection to infants, especially during the high-risk first 6 months of life, through passive transplacental antibody transfer.[2] Recent studies of COVID-19 vaccination during pregnancy suggest the possibility of transplacental transfer of SARS-CoV-2–specific antibodies that might provide protection to infants;[3–5]however, no epidemiologic evidence currently exists for the protective benefits of maternal immunization during pregnancy against COVID-19 in infants. The Overcoming COVID-19 network conducted a test-negative, case-control study at 20 pediatric hospitals in 17 states during July 1, 2021–January 17, 2022, to assess effectiveness of maternal completion of a 2-dose primary mRNA COVID-19 vaccination series during pregnancy against COVID-19 hospitalization in infants. Among 379 hospitalized infants aged <6 months (176 with COVID-19 [case-infants] and 203 without COVID-19 [control-infants]), the median age was 2 months, 21% had at least one underlying medical condition, and 22% of case- and control-infants were born premature (<37 weeks gestation). Effectiveness of maternal vaccination during pregnancy against COVID-19 hospitalization in infants aged <6 months was 61% (95% CI = 31%–78%).

*These authors contributed equally to this report.
These senior authors contributed equally to this report.
§ https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html.
https://covid.cdc.gov/covid-data-tracker/#variant-proportions
**Symptomatic COVID-19–like illness was defined as one or more of the following: fever, cough, shortness of breath, gastrointestinal symptoms (e.g., diarrhea, vomiting, or "stomachache"), use of respiratory support (high-flow oxygen by nasal cannula, new invasive or noninvasive ventilation) for the acute illness, or new pulmonary findings on chest imaging consistent with pneumonia. Four case-infants tested at an outside hospital or other facility had some missing data on positive test results and were not retested at the study hospital.
††Mothers were defined as vaccinated after completing their 2-dose primary mRNA COVID-19 vaccine series during pregnancy, including both doses received during pregnancy or the first dose received before pregnancy and the second dose, completing their primary series, received during pregnancy. Data on maternal moderately or severely immunocompromising conditions were not recorded for mothers of enrolled infants to determine whether mothers needed an additional mRNA COVID-19 vaccine dose to complete their primary series.
§§45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect 241(d); 5 U.S.C. Sect 552a; 44 U.S.C. Sect 3501 et seq.
¶¶Other reasons for excluding infants from the analysis included May or June hospital admission (two); birth to mothers who received Janssen (Johnson & Johnson) COVID-19 vaccine (four), who received their second dose of vaccine <14 days before delivery (three), who received a 2-dose primary mRNA COVID-19 vaccine before pregnancy (seven), or with unknown vaccination status (one); infants who received a positive SARS-CoV-2 test result but were admitted for non–COVID-19 reasons (four); and SARS-CoV-2 testing >10 days after illness onset or >3 days from hospitalization (two).

Recommendations

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