Preventing respiratory syncytial virus (RSV) infection in young children

The Canadian Paediatric Society has published guidance on prevention of respiratory syncytial virus (RSV) in young children for the 2024-2025 viral respiratory illness season. RSV is one of the most common respiratory viruses infecting infants and young children and the leading cause of bronchiolitis. By age two, most children will have been infected with RSV. It can cause severe lung infections, especially in young infants; these infections may require hospitalization, intensive care unit level care, and can be fatal.No specific treatment is available for RSV, but pharmacologic measures can prevent infection. Palivizumab (Synagis), a monoclonal antibody, has been recommended by the National Advisory Committee on Immunization (NACI) since 2003 for prevention of RSV disease in a select group of high-risk infants. However, it must be administered every four to six weeks throughout the RSV season (typically four doses given from November through March).New prevention strategiesNACI now recommends building toward a universal RSV prevention program for all infants. Two new strategies are now recommended to prevent severe RSV infection in infants:Nirsevimab (Beyfortis). This monoclonal antibody is administered once during the RSV season and offers direct passive antibody protection for the duration of that season.RSV stabilized prefusion F subunit vaccine (Abrysvo). This vaccine is given during the third trimester of pregnancy (between 32 and 36 weeks gestation), to provide infants with passive protection via transplacental antibody transfer to the fetus.NACI currently prefers nirsevimab over Abrysvo, based on reported efficacy (including duration of protection) and safety data. Efficacy for prevention of RSV infection requiring hospitalization had been reported as 76.8–81% at 150 days for nirsevimab and 57% at 180 days for Abrysvo.The Canadian Paediatric Society suggests that while provincial/territorial RSV prevention programs using these newer agents are being established in Canada, healthcare providers should advocate to ensure that the most vulnerable infants are prioritized for protection.Children who should be prioritized to receive nirsevimabThose at risk for severe RSV disease or who, in the event of severe RSV disease, may face significant limitations to accessing the required critical care support. This would include infants born during or infants entering their first RSV season who have risk factor(s) for severe RSV disease; were born before 37 weeks gestational age; face complex transportation issues for treatment of severe RSV disease; and infants entering their second RSV season whose medical condition continues to place them at ongoing risk for severe RSV disease. Infants at increased risk of severe RSV disease during their first RSV season would include:all premature infants (i.e., born < 37 weeks gestational age)those with chronic lung disease, including bronchopulmonary dysplasia, requiring ongoing assisted ventilation, oxygen therapy, or chronic medical therapy in the six months prior to the start of the RSV seasonthose with cystic fibrosis with respiratory involvement and/or growth delaythose with hemodynamically significant chronic cardiac disease, severe immunodeficiency, severe congenital airway anomalies impairing clearing of respiratory secretions, neuromuscular disease impairing clearing of respiratory secretions or Down syndrome. Infants at ongoing risk of severe RSV disease during their second RSV season would include:all those listed above, except for infants born at less than 37 weeks gestational age and infants with Down syndrome who do not have another medical condition listed above.If cost-effective, nirsevimab should be considered for any infant younger than eight months of age entering (or born during) their first RSV season through universal immunization programs.Who should receive Abrysvo?Abrysvo is administered during pregnancy to provide infants with passive protection for their first few months of life via transplacental antibody transfer. Abrysvo has a narrow window for administration (32-to-36 weeks gestational age), and is most effective if administered at least two weeks before delivery.NACI is not currently recommending a universal RSV immunization program with Abrysvo during pregnancy. However, pregnant persons may consider vaccination with Abrysvo on an individual basis to prevent severe RSV disease in their infant’s first few months of life. When Abrysvo is administered during pregnancy, infants do not require nirsevimab unless they meet medical criteria for increased risk of severe RSV disease (listed above), or were born less than two weeks after administration of Abrysvo.The most frequent adverse effects of Abrysvo in pregnant persons are pain at the injection site, headache and myalgia. When administered in pregnancy in clinical trials, Abrysvo did not result in an increase in severe systemic adverse effects among infants compared with placebo. However, it is uncertain whether Abrysvo increases the risk of preterm birth; giving the vaccine at 32-to-36 weeks gestational age should minimize any potential risk.SummaryThe Canadian Paediatric Society notes that availability of these preventive measures will vary across Canada because product purchasing and administration decisions are made at the provincial/territorial level. Pediatricians and other healthcare providers have a crucial role in advocating for equitable access to RSV preventive therapies. They should keep informed about available agents within their jurisdiction and counsel and support individual decisions that maximize protection against RSV. Children at the highest risk for severe RSV disease should be prioritized, including those in northern, remote and rural areas of Canada, where the potential health benefits and cost-effectiveness of these measures may be greatest. Until nirsevimab becomes part of preventive programs, provinces and territories should continue to offer palivizumab to infants at high risk of severe RSV disease.Reference:Comeau JL, Moore DL, Barton MA; Canadian Paediatric Society, Infectious Diseases and Immunization Committee. Respiratory syncytial virus (RSV) prevention strategies for the 2024-2025 viral respiratory illness season. (accessed Nov. 21, 2024).

Preventing respiratory syncytial virus (RSV) infection in young children

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