Respiratory syncytial virus (RSV) has a predilection for invading the upper and lower respiratory tract and affecting young children and infants (who commonly are hospitalized for hypoxia and dehydration), thereby adding significant costs to health care in the United States.
Doctors Glenn-Otto and Dziacky in the April issue of Pediatrics in Review give a brief yet informative review of the trials and tribulations of trying to prevent RSV infection.
Developing an effective RSV vaccine is a challenge; multiple attempts since the 1960s have been unsuccessful. A formalin inactivated vaccine left children in an experimental group with more severe symptoms than those in a control group; 2 children died when naturally exposed to RSV, and children in the experimental group did not develop neutralizing antibodies when compared to children with natural infection. Just as challenging is balancing immunogenicity with minimal side effects in a live attenuated vaccine.
At present, passive immunity shows better promise. Nirsevimab, a human recombinant monoclonal antibody approved by the FDA in 2023, significantly prevents RSV infection in infants and young children. In a randomized control trial, nirsevimab reduced lower respiratory tract infection.
The American Academy of Pediatrics and the Advisory Committee on Immunization Practices (ACIP) recommend nirsevimab for infants who are less than 8 months of age with unvaccinated or unknown maternal RSV status or born less than 14 days of maternal vaccination right before or during RSV season. High risk infants with chronic lung disease (CLD), severe immunocompromise, cystic fibrosis with manifestations of severe lung disease or weight-for-length <10th percentile or American Indian or Alaska Native descent should receive a 2nd dose as they enter their second RSV season. A previous RSV infection is not a contraindication for nirsevimab.
Not to forget though, palivizumab has been in use since 1998, but due to its shorter half-life and only 55% relative reduction in hospitalizations, it is recommended only for premature infants less than 28 weeks and for infants with CLD or congenital heart disease.
Another noteworthy strategy to prevent RSV infection in infants includes maternal vaccination during pregnancy, which can be effective for the delivered infant up to 6 months of age, although immunity wanes as the infant gets older.
