Despite the increasing availability of vaccines to prevent COVID-19, one age group still remains more vulnerable to severe illness: infants (1). Ineligible for the vaccine until six months of age, infants experience a significant immunity gap, resulting in a higher chance of contracting COVID-19 and then suffering severe infection (2). Compared to older children, infants under six months of age comprise a significantly larger proportion of COVID-19 hospitalizations and deaths — for example, during the peak of the extremely contagious omicron variant, infants composed 44% of all COVID-related hospitalizations among children aged four or younger (3). Factors such as lack of vaccination, smaller airways, and immaturity of the respiratory and immune systems contribute to this higher percentage, leading to a higher risk of infection, pneumonia, respiratory failure and death in infants (4). While infant COVID-19 vaccines have not been approved, one method has been shown to provide some immunity to infants — maternal vaccination during pregnancy (5).

While the idea of inoculating pregnant people against COVID-19 was initially met with scrutiny and concerns about potential side effects, researchers and the Centers for Disease Control and Prevention highlighted the safety of other vaccines during pregnancy, such as the Tdap (tetanus-diphtheria-pertussis) and influenza immunizations (6). Although the original Pfizer and Moderna clinical trials excluded pregnant people, more recent studies have shown that pregnant women who received doses of either of the FDA-approved COVID-19 vaccines did not experience higher rates of adverse pregnancy outcomes or birth complications compared to unvaccinated pregnant women (7) — in contrast, contracting COVID-19 during pregnancy is associated with increased risk of complications, such as preterm birth, stillbirth, maternal cardiomyopathy, and loss of pregnancy (8). Thus, maternal vaccination against COVID-19 can offer immunity to both the parent and the unborn infant.

In addition to protecting pregnant people and their unborn infants, COVID-19 vaccination also protects infants after birth. A major study performed by the Overcoming COVID-19 Network in 2022 explored the relationship between maternal vaccination and infant immunity, discovering that infants born to women vaccinated during pregnancy demonstrated significant levels of antibodies against COVID-19 through the first six months of life (9, 10). Maternal antibodies were identified in umbilical cord blood, breast milk, and serum specimens from infants, indicating that antibody transfer had occurred through the placenta (9). Moreover, infants born to vaccinated mothers exhibited higher levels of protective anti-spike antibodies compared to infants born to unvaccinated mothers or mothers who had sustained a natural infection of COVID-19 during pregnancy (9). Overall, the researchers found that the efficacy of maternal vaccination during pregnancy against infant COVID-19 hospitalization was 38% during the omicron wave, 80% during the delta wave, and 52% overall (9). Notably, efficacy was highest when mothers had achieved full vaccination after the first trimester (9). Most shockingly, the vast majority — 90% — of infants in the study who were admitted to the ICU for COVID-19 complications were born to unvaccinated mothers, while all of the infants who died were born to unvaccinated mothers (9).

This study emphasizes the power of COVID-19 vaccines, both for preventing severe disease in pregnant people as well as infants. However, the COVID-19 vaccination rate among pregnant women remains low at 71% (9). Researchers, the CDC, professional obstetrics and gynecology associations, and healthcare practitioners recommend that pregnant people seek COVID-19 vaccination in order to protect not only themselves, but their infants too (9). Conversations with medical practitioners and being able to see safety data have been shown to increase the likelihood of vaccination in pregnant women; therefore, researchers recommend that healthcare teams engage in honest, open discussions about vaccination with pregnant people to ensure that they have enough information to make a decision (10).

References

1: Bialek, S., Gierke, R., Hughes, M., McNamara, L., Pilishvili, T., Skoff, T. and CDC COVID-19 Response Team. (2020). Coronavirus disease 2019 in children — United States, February 12-April 2, 2020. Morbidity and Mortality Weekly Report, vol. 10, pp. 422-426. DOI: 10.15585/mmwr.mm6914e4.

2: Hobbs, C., Woodworth, K., Young, C., Jackson, A., Newhams, M., Dapul, H., Maamari, M., Hall, M., Maddux, A., Singh, A., Schuster, J., Rowan, C., Fitzgerald, J., Irby, K., Kong, M., Mack, E., Staat, M., Cvijanovich, N., Bembea, M., Coates, B., Halasa, N., Walker, T., McLaughlin, G., Babbitt, C., Nofziger, R., Loftis, L., Bradford, T., Campbell, A., Patel, M. and Randolph, A. (2022). Frequency, characteristics and complications of COVID-19 in hospitalized infants. Pediatric Infectious Diseases Journal, vol. 41, pp. e81-e86. DOI: 10.1097/INF.0000000000003435.

3: Marks, K., Whitaker, M., Agathis, N., Anglin, Ok., Milucky, J., Patel, K., Pham, H., Kirley, P., Kawasaki, B., Meek, J., Anderson, E., Weigel, A., Kim, S., Lynfield, R., Ropp, S., Spina, N., Bennett, N., Schiltz, E., Sutton, M., Talbot, H., Price, A., Taylor, C., Havers, F. and COVID-NET Surveillance Team. (2022). Hospitalization of infants and children aged 0-4 years with laboratory-confirmed COVID-19 — COVID-NET, 14 states, March 2020-February 2022. Morbidity and Mortality Weekly Report, vol. 71. DOI: 10.15585/mmwr.mm7111e2.

4: Kloc, M., Ghobrial, R., Kuchar, E., Lewicki, S. and Kubiak, J. (2020). Development of child immunity in the context of COVID-19 pandemic. Clinical Immunology, vol. 217. DOI: 10.1016/j.clim.2020.108510.

5: Trostle, M., Aguero-Rosenfield, M., Roman, A. and Lighter, J. (2021). High antibody levels in cord blood from pregnant women vaccinated against COVID-19. American Journal of Obstetrics and Gynecology, vol. 3. DOI: 10.1016/j.ajogmf.2021.100481.

6: Lindley, M., Kahn, Katherine, Bardenheier, B. D’Angelo, D., Dawood, F., Fink, R. and Skoff, T. (2019). Vital signs: burden and prevention of influenza and pertussis among pregnant women and infantes — United States. Morbidity and Mortality Weekly Report, vol. 68, pp. 885-892. DOI: 10.15585/mmwr.mm6840e1.

7: Fell, D., Dhinsa, T., Alton, G., Torok, E., Cruz, S., Regan, A., Sprague, A., Buchan, S., Kwong, J., Wilson, S., Haberg, S., Gravel, C., Wilson, K., El-Chaar, D., Walker, M., Barrett, J., MacDonald, S., Okun, N., Shah, P., Dougan, S., Dunn, S. and Bisnaire, L. (2022). Association of COVID-19 vaccination in pregnancy with adverse peripartum outcomes. JAMA, vol. 327, pp. 1478-1487. DOI: 10.1001/jama.2022.4255.

8: Metz, T., Clifton, R., Hughes, B., Sandoval, G., Grobman, A., Saade, G., Manuck, T., Longo, M., Sowles, A., Clark, K., Simhan, H., Rouse, D., Mendez-Figueroa, H., Gyamfi-Bannerman, C., Bailit, J., Costantine, M., Sehdev, H., Tita, A. and Macones, G. (2022). Association of SARS-CoV-2 infection with serious maternal morbidity and mortality from obstetric complications. JAMA, vol. 327, pp. 748-759. DOI: 10.1001/jama.2022.1190.

9: Halasa, N., Olson, N., Staat, M., Newhams, M., Price, A., Pannaraj, P., Boom, J., Sahni, L., Chiotos, K., Cameron, M., Bline, K., Hobbs, C., Maddux, A., Coates, B., Michelson, K., Heidemann, S., Irby, K., Nofziger, R., Mack, E., Smallcomb, L., Schwartz, S., Walker, T., Gertz, S., Schuster, J., Kamidani, S., Tarquinio, K., Bhumbra, S., Maamari, M., Hume, J., Crandall, H., Levy, E., Zinter, M., Bradford, T., Flori, H., Cullimore, M., Kong, M., Cvijanovich, N., Gilboa, S., Polen, K., Campbell, A., Randolph, A. and Patel, M. (2022). Maternal vaccination and risk of hospitalization for COVID-19 among infants. New England Journal of Medicine, vol. 387, pp. 109-119. DOI: 10.1056/NEJMoa2204399.

10: Rasmussen, S. and Jamieson, D. (2022). COVID-19 vaccination during pregnancy — two for the price of one. New England Journal of Medicine, vol. 387, pp. 178-179. DOI: 10.1056/NEJMe2206730.