The early data have been very clear: when the long-acting monoclonal antibody nirsevimab is administered to infants during their first respiratory syncytial virus (RSV) season, it is very effective in preventing hospitalization for RSV infection. However, it has been less clear whether less severe RSV infections not requiring hospitalizations are also prevented when infants receive nirsevimab.
In an article and accompanying video abstract being early released this week in Pediatrics, entitled “Nirsevimab Effectiveness Against Severe Respiratory Syncytial Virus Infection in the Primary Care Setting,” Mónica López-Lacort, MSc, Cintia Muñoz-Quiles, PhD, and colleagues in the MEDIPRIM network of primary care centers in Spain explore this question (10.1542/peds.2024-066393).
The authors enrolled 160 infants who were seen for cold symptoms by their primary care provider between November 2023 and February 2024; all infants were born after April 1, 2023, and had at least one sign of a lower respiratory tract infection:
- Rhonchi
- Rales
- Crackles
- Wheeze
- Apnea
Nasopharyngeal or oropharyngeal swabs were sent for testing by polymerase chain reaction (PCR). The authors then looked at the vaccination history of each of the infants in the study.
Infants who had received nirsevimab were much more likely to have RSV-negative PCRs at the time of their cold symptoms.
In fact, the authors calculated a 76% rate of effectiveness for nirsevimab in preventing RSV lower respiratory tract infections that require a visit to a primary care site. Additionally, those who received nirsevimab at 1 to 8 months of age were equally—and maybe even more—protected against RSV infection! These results also align with earlier data that have demonstrated a 75–80% protection against hospitalization for RSV infection.
This is excellent news for our youngest patients—and leads us to hope for a less severe respiratory season!
