Effectiveness of Maternal Vaccination with mRNA COVID-19 Vaccine During Pregnancy Against COVID-19–Associated Hospitalization in Infants Aged &lt;6 Months — 17 States, July 2021–January 2022
Authors: Natasha B. Halasa, Samantha M. Olson, Mary A. Staat, Margaret M. Newhams, Ashley M. Price, Julie A. Boom, Leila C. Sahni, Melissa A. Cameron, Pia S. Pannaraj, Katherine E. Bline, Samina S. Bhumbra, Tamara T. Bradford, Kathleen Chiotos, Bria M. Coates, Melissa L. Cullimore, Natalie Z. Cvijanovich, Heidi R. Flori, Shira J. Gertz, Sabrina M. Heidemann, Charlotte V. Hobbs, Janet R. Hume, Katherine Irby, Satoshi Kamidani, Michele Kong, Emily R. Levy, Elizabeth H. Mack, Aline B. Maddux, Kelly N. Michelson, Ryan A. Nofziger, Jennifer E. Schuster, Stephanie P. Schwartz, Laura Smallcomb, Keiko M. Tarquinio, Tracie C. Walker, Matt S. Zinter, Suzanne M. Gilboa, Kara N. Polen, Angela P. Campbell, Adrienne G. Randolph, Manish M. Patel, Laura D. Zambrano, Meghan Murdock, Mary Glas Gaspers, Connor P. Kelley, Katri V. Typpo, Peter M. Mourani, Ronald C. Sanders, Chelsea Smith, Masson Yates, Katheryn Crane, Geraldina Lionetti, Juliana Murcia-Montoya, Denise Villarreal-Chico, Daniel Hakimi, Adam L. Skura, Imogene Carson, Justin M. Lockwood, Emily Port, Brandon M. Chatani, Nadine Baida, Laila Hussaini, Hassan A. Khan, Simone T. Rhodes, Courtney M. Rowan, Mary Stumpf, Marla S. Johnston, Laura Berbert, Benjamin J. Boutselis, Sabrina R. Chen, Jie He, Suden Kucukak, Timothy P. McCadden, Amber O. Orzel, Edie Weller, Patrick Moran, Ellen R. Bruno, Lexie A. Goertzen, Supriya Behl, Noelle M. Drapeau, Lacy Malloch, Lora Martin, April Palmer, Roberto P. Santos, Abigail Kietzman, Melissa Sullivan, Lauren A. Hoody, Valerie H. Rinehart, Paris C. Bennett, Merry L. Tomcany, Nicole A. Twinem, Chelsea C. Rohlfs, Amber Wolfe, Rebecca L. Douglas, Kathlyn Phengchomphet, Megan M. Bickford, Lauren E. Wakefield, Meena Golchha, Laura S. Stewart, Jennifer N. Oates, Cindy Bowens, Mia Maamari
Journal: MMWR Morbidity and Mortality Weekly Report (2022)

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%). Completion of a 2-dose mRNA COVID-19 vaccination series during pregnancy might help prevent COVID-19 hospitalization among infants aged <6 months.