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
MMWR Recommendations and Reports
Infants aged <6 months are not eligible for COVID-19 vaccination. Vaccination during pregnancy has been associated with protection against infant 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 <6 months and a subset of infants aged <3 months. VE was calculated as (1 – adjusted odds ratio) x 100% among all infants aged <6 months and <3 months. Case-patients (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 <6 months and 54% (95% CI = 32%–68%) among infants aged <3 months. Intensive care unit admissions occurred in 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 <3 months. Expectant mothers should remain current with COVID-19 vaccination to protect themselves and their infants from hospitalization and severe outcomes associated with COVID-19.
Simeone, Regina M.; Zambrano, Laura D.; Halasa, Natasha B.; Fleming-Dutra, Katherine E.; Newhams, Margaret M.; Wu, Michael J.; Orzel-Lockwood, Amber O.; Kamidani, Satoshi; Pannaraj, Pia S.; Irby, Katherine; Maddux, Aline B.; Hobbs, Charlotte V.; Cameron, Melissa A.; Boom, Julie A.; Sahni, Leila C.; Kong, Michele; Nofziger, Ryan A.; Schuster, Jennifer E.; Crandall, Hillary; Hume, Janet R.; Staat, Mary A.; Mack, Elizabeth H.; Bradford, Tamara T.; Heidemann, Sabrina M.; Levy, Emily R.; Gertz, Shira J.; Bhumbra, Samina S.; and Walker, Tracie C., "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" (2023). School of Medicine Faculty Publications. 1566.