Effectiveness of Maternal mRNA COVID-19 Vaccination During Pregnancy Against COVID-19–Associated Hospitalizations in Infants Aged <6 Months During SARS-CoV-2 Omicron Predominance — 20 States, March 9, 2022–May 31, 2023


Regina M. Simeone, National Center for Immunization and Respiratory Diseases
Laura D. Zambrano, National Center for Immunization and Respiratory Diseases
Natasha B. Halasa, Vanderbilt University Medical Center
Katherine E. Fleming-Dutra, National Center for Immunization and Respiratory Diseases
Margaret M. Newhams, Boston Children's Hospital
Michael J. Wu, National Center for Immunization and Respiratory Diseases
Amber O. Orzel-Lockwood, Boston Children's Hospital
Satoshi Kamidani, Emory University School of Medicine
Pia S. Pannaraj, Children's Hospital Los Angeles
Katherine Irby, Arkansas Children's Hospital
Aline B. Maddux, University of Colorado School of Medicine
Charlotte V. Hobbs, University of Mississippi Medical Center
Melissa A. Cameron, University of California, San Diego
Julie A. Boom, Texas Children's Hospital
Leila C. Sahni, Texas Children's Hospital
Michele Kong, The University of Alabama at Birmingham
Ryan A. Nofziger, Akron Children's Hospital
Jennifer E. Schuster, Children's Mercy Kansas City
Hillary Crandall, University of Utah School of Medicine
Janet R. Hume, University of Minnesota Twin Cities
Mary A. Staat, University of Cincinnati College of Medicine
Elizabeth H. Mack, Medical University of South Carolina
Tamara T. Bradford, LSU Health Sciences Center - New OrleansFollow
Sabrina M. Heidemann, Central Michigan University
Emily R. Levy, Mayo Clinic
Shira J. Gertz, Cooperman Barnabas Medical Center
Samina S. Bhumbra, Indiana University School of Medicine
Tracie C. Walker, UNC School of Medicine

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MMWR Recommendations and Reports


Infants aged COVID-19–related hospitalization. The Overcoming COVID-19 Network conducted a case-control study during March 9, 2022–May 31, 2023, to evaluate the effectiveness of maternal receipt of a COVID-19 vaccine dose (vaccine effectiveness [VE]) during pregnancy against COVID-19–related hospitalization in infants aged (1 – adjusted odds ratio) x 100% among all infants aged (infants hospitalized for COVID-19 outside of birth hospitalization and who had a positive SARS-CoV-2 test result) and control patients (infants hospitalized for COVID-19–like illness with a negative SARS-CoV-2 test result) were compared. Odds ratios were determined using multivariable logistic regression, comparing the odds of receipt of a maternal COVID-19 vaccine dose (completion of a 2-dose vaccination series or a third or higher dose) during pregnancy with maternal nonvaccination between case- and control patients. VE of maternal vaccination during pregnancy against COVID-19–related hospitalization was 35% (95% CI = 15%–51%) among infants aged 54% (95% CI = 32%–68%) among infants aged 23% of all case-patients, and invasive mechanical ventilation was more common among infants of unvaccinated (9%) compared with vaccinated mothers (1%) (p = 0.02). Maternal vaccination during pregnancy provides some protection against COVID-19–related hospitalizations among infants, particularly those aged COVID-19.

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