RSVpreF (Abrysvo) and Nirsevimab-alip (Beyfortus) for the Prevention of Respiratory Syncytial Virus Infection

RSVpreF (Abrysvo) is a respiratory syncytial virus (RSV) vaccine. It induces antibodies to the viral surface protein (protein F) that attaches the virus to host cells. RSVpreF is labeled for active immunization of individuals 60 years and older for the prevention of lower respiratory tract infection (LRTI). It is also labeled for use in pregnant individuals to prevent severe LRTI caused by RSV in infants in the first 6 months of life. Passive immunization occurs through transplacental transfer of maternal antibodies to infants.¹ Nirsevimab-alip (Beyfortus) is an anti-RSV monoclonal antibody indicated for infants entering their first RSV season and children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.²

RSVpreF was evaluated for safety in approximately 4,000 maternal participants and 17,215 participants 60 years and older.¹ In pregnant patients at increased risk of preterm delivery, RSVpreF should be administered between 32 and 36 weeks of gestation to mitigate the risk of preterm birth before 32 weeks.¹ As with other injectable vaccines, there is a risk of syncope.

Nirsevimab-alip has been studied for safety in 3,224 infants. Because it is a monoclonal antibody, there is a theoretical risk of anaphylaxis, although no events were reported in clinical trials.²

The most common adverse effect from RSVpreF was pain at the injection site, which occurred in 40.6% of vaccinated patients vs. 10.1% of patients receiving placebo. Fatigue, headache, muscle pain, and nausea are also possible, although these occurred at a rate similar to that of placebo.¹ Rash and injection site reaction can occur with nirsevimabalip but are uncommon.²

Active immunization with RSVpreF in pregnant individuals reduced medically attended RSV-associated LRTI (number needed to treat [NNT] = 58; 95% CI, 45 to 101), severe LRTI (NNT = 81; 95% CI, 67 to 101), and hospitalizations of their infants (NNT = 139; 95% CI, 98 to 783) through 180 days after birth.^1,3

The effectiveness of vaccination with RSVpreF in the first RSV season compared with placebo was studied in adults 60 years and older, with approximately 16,300 participants in each group.¹ RSVpreF reduced the first occurrence of RSV-positive LRTI in the first RSV season. However, the NNT to prevent one RSV-associated LRTI was approximately 740 participants (95% CI, 575 to 1,716) for LRTI with more than two symptoms, and approximately 1,360 participants (95% CI, 1,180 to 3,640) for LRTI with more than three symptoms. There was no significant reduction in severe LRTI, defined by hospitalization, the requirement of supplemental oxygen, or mechanical ventilation, because there were only two cases of severe LRTI reported in the placebo group and none in the RSVpreF group.¹

Nirsevimab-alip reduced the incidence of RSV-positive LRTI requiring medical attention in infants born after 35 weeks of gestation from 5.0% to 1.2% (NNT = 26; 95% CI, 23 to 39) compared with placebo through 150 days after administration.^2,4 In infants born after 29 weeks of gestation entering their first RSV season, nirsevimab-alip may reduce RSV-associated hospitalizations and severe RSV-associated LRTI, defined by hypoxia with oxygen saturation less than 90%.^2,5 Effectiveness was defined as relative risk reduction against placebo and adjusted for age at randomization. Although not directly compared, nirsevimab-alip is as effective as palivizumab (Synagis) for preventing medically attended RSV-associated LRTI in season 1 of RSV and possibly in season 2 among high-risk infants with chronic lung disease, chronic heart disease, or preterm birth at less than 35 weeks of gestation.²

RSVpreF costs about $300 per dose. It is covered under Medicare Part D; however, coverage may vary for Medicare Advantage and other insurance plans.

Under the Vaccines for Children program, nirsevimabalip is covered for children up to 24 months of age. The cost of nirsevimab-alip is about $500 per 50- or 100-mg dose.⁶ This is significantly less expensive than palivizumab, which costs about $1,000 per dose and requires up to five doses per RSV season.

RSVpreF is administered as a single-dose 0.5-mL intramuscular injection of reconstituted solution for pregnant individuals between 32 and 36 weeks of gestation and patients 60 years or older.¹

The recommended dose of nirsevimab-alip for the first RSV season is 50 mg for infants weighing less than 5 kg (2.2 lb) and 100 mg for infants weighing 5 kg or more. For children up to 24 months of age who remain at increased risk of severe RSV disease and are entering their second RSV season, the recommended dose of nirsevimab-alip is 200 mg, which can be administered via two 100-mg intramuscular injections.²

RSVpreF and nirsevimab-alip are effective for the prevention of RSV-associated LRTI, severe LRTI, and hospitalizations in infants entering their first RSV season. The Centers for Disease Control and Prevention and the American Academy of Family Physicians (AAFP) recommend bivalent RSVpreF vaccination for pregnant individuals between 32 and 36 weeks of gestation, with seasonal administration from September through January. For high-risk infants who are traditionally candidates for palivizumab, the longer duration of nirsevimab-alip provides a more convenient and affordable option with a single dose vs. palivizumab, which requires monthly doses during RSV season. The AAFP recommends that physicians use shared clinical decision-making with adults 60 years and older when considering RSVpreF administration. RSVpreF also may be considered in patients with conditions that increase the risk of severe RSV, including chronic cardiopulmonary diseases, immunocompromised status, diabetes mellitus, chronic kidney and lung disease, neuromuscular disorders, and other factors such as frailty or residence in a nursing home or long-term care facility.