Top 5 Takeaways

1. Maternal Vaccination Effectiveness: The effectiveness of maternal completion of a 2-dose primary mRNA COVID-19 vaccination series during pregnancy against COVID-19 hospitalization among infants aged <6 months was 61%.
2. Timing of Vaccination: Vaccination effectiveness was 32% when completed early in pregnancy and 80% when completed later in pregnancy.
3. Infant Hospitalization Risk: Among 176 infants hospitalized with COVID-19, 84% were born to unvaccinated mothers.
4. Maternal Vaccination Recommendation: COVID-19 vaccination is recommended for pregnant women to protect both the mother and infant from severe COVID-19 complications.
5. Study Limitations: Limitations include inability to assess vaccine effectiveness against specific variants and small sample sizes for certain analyses.

Original Article Author and Citation

Corresponding Author

Samantha M. Olson, ylz8@cdc.gov

Suggested Citation

Halasa NB, Olson SM, Staat MA, et al. 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. MMWR Morb Mortal Wkly Rep 2022;71:264–270. DOI: http://dx.doi.org/10.15585/mmwr.mm7107e3

Summary

This study assessed the effectiveness of maternal COVID-19 vaccination during pregnancy in preventing COVID-19-associated hospitalization in infants aged <6 months. The study found that maternal vaccination was 61% effective overall, with higher effectiveness when vaccination was completed later in pregnancy. The findings support the recommendation for COVID-19 vaccination during pregnancy to protect both mothers and their infants from severe COVID-19 complications.

Methods

The study used a test-negative, case-control design involving 379 infants hospitalized in 20 pediatric hospitals across 17 states from July 1, 2021, to January 17, 2022. Infants were categorized as case-infants (hospitalized with COVID-19) or control-infants (hospitalized without COVID-19). Maternal vaccination status was verified through documentation and interviews. Vaccine effectiveness was calculated using logistic regression models adjusted for various factors.

Discussion

The findings indicate that maternal vaccination during pregnancy is associated with a reduced risk of COVID-19 hospitalization in infants aged <6 months. The higher effectiveness observed when vaccination was completed later in pregnancy suggests the potential benefit of transplacental antibody transfer. The study highlights the importance of maternal vaccination to protect infants, especially given their ineligibility for vaccination and high hospitalization rates during the pandemic.

Conclusion

Maternal completion of a 2-dose mRNA COVID-19 vaccination series during pregnancy is associated with a significant reduction in COVID-19-associated hospitalization in infants aged <6 months. These findings support current recommendations for COVID-19 vaccination during pregnancy to protect both mothers and their infants from severe COVID-19 outcomes.

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