The RSVpreF vaccine maintained its effectiveness against RSV-related lower respiratory tract illnesses with at least three symptoms during the 2nd season – with vaccine effectiveness estimated at 77,8 % (95% CI: 51.4 to 91.1) – and during both seasonswith an efficiency of 81,5 % (95% CI: 63.3 to 91.6). Efficacy was good against the two circulating antigenic subgroups (RSV A and RSV B): respectively 80.6% (95% CI: 52.9 to 93.4) and 86.4% (95% CI: 54.6 at 97.4) during the two epidemic seasons.
However, as observed during the first season, the vaccine performed less well against less serious diseases (patients with at least two symptoms) during the 2nd season.
Likewise, the effectiveness observed over the two seasons was higher against forms with at least three symptoms in participants aged 60 to 69 (81.6%) and those aged 70 to 79 (72.7%) than against diseases with at least two symptoms (57, 5% and 62.5% respectively). Finally, protection against very symptomatic forms would be 100% in those over 80, although the low number of cases and wide confidence intervals limit the interpretation of the data.
These results suggest that one dose of vaccine should protect seniors against the most symptomatic RSV infections for at least two epidemic seasons. Thus, a vaccination every 2 years could be sufficient. However, it is a shame not to have collected data on hospitalizations in this study.
