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RSV Vaccine During Pregnancy to Prevent RSV Infection in Infants

08:01 09 September in Blog

Human respiratory syncytial virus (RSV) is one of the common viruses that cause acute respiratory tract infection in infants and children leading to hospitalization 1,2. RSV infection mainly manifests as bronchiolitis and may progress to pneumonia 1,2. Symptoms include coryza, congestion, cough, and tachypnea. Worldwide, 34 million children younger than age 5 years were reported to develop lower respiratory tract infection because of RSV; 10% are hospitalized for severe disease. The WHO reports that there are between 66,000 and 253,000 RSV-associated deaths annually 3,4.

Recently, the FDA approved Abrysvo® for pregnant individuals to prevent lower respiratory tract disease and severe lower respiratory tract disease caused by RSV in infants from birth through 6 months of age. Abrysvo® is the first vaccine to be approved for this indication. It is given intramuscularly between weeks 32 and 36 of pregnancy 5.

Safety and effectiveness of Abrysvo® were evaluated in a phase 3, double-blind trial conducted in 18 countries. It reduced the risk of medically attended severe respiratory tract infection in infants by 81.8% and 69.4% within 90 and 180 days after birth, respectively 6. In a subgroup analysis of pregnant women (34 to 36 weeks of pregnancy), Abrysvo® reduced the risk of lower respiratory tract infection and severe lower respiratory tract infection within 90 days after birth by 34.7% and 91.1%, respectively. Similarly, the vaccine was able to reduce the risk of lower respiratory tract infection and severe lower respiratory tract infection within 180 days after birth by 57.3% and 76.5%, respectively. No safety signals were detected and the adverse events were comparable between the vaccine and placebo groups 6.

In its approval announcement, the FDA noted that preeclampsia occurred in 1.8% of the vaccine group compared to 1.4% of placebo group 5. The announcement has also reported that that in infants, low birth weight and jaundice occurred at a higher rate among the pregnant women who received Abrysvo® compared to the placebo group. The FDA also warned about the “numerical imbalance” in preterm births in the Abrysvo® group (5.7%) compared to those who received placebo (4.7%). “The available data are insufficient to establish or exclude a causal relationship between preterm birth and Abrysvo®”, the FDA added 5.

Overall, Abrysvo® may provide a good option for preventing RSV-associated respiratory tract infections in infants.


1.         Domachowske J, Halczyn J, Bonville CA. Preventing Pediatric Respiratory Syncytial Virus Infection. Pediatr Ann. 2018;47(9):e371-e376. doi:10.3928/19382359-20180816-01

2.         Jain H, Schweitzer JW, Justice NA. Respiratory Syncytial Virus Infection. In: StatPearls. StatPearls Publishing; 2023. Accessed August 31, 2023.

3.         Nair H, Nokes DJ, Gessner BD, et al. Global burden of acute lower respiratory infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis. Lancet Lond Engl. 2010;375(9725):1545-1555. doi:10.1016/S0140-6736(10)60206-1

4.         Modjarrad K, Giersing B, Kaslow DC, Smith PG, Moorthy VS, WHO RSV Vaccine Consultation Expert Group. WHO consultation on Respiratory Syncytial Virus Vaccine Development Report from a World Health Organization Meeting held on 23-24 March 2015. Vaccine. 2016;34(2):190-197. doi:10.1016/j.vaccine.2015.05.093

5.         Commissioner O of the. FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants. FDA. Published August 22, 2023. Accessed August 31, 2023.

6.         Kampmann B, Madhi SA, Munjal I, et al. Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants. N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480