IMPACT OF NIRSEVIMAB ON RSV AND NON-RSV SEVERE RESPIRATORY INFECTIONS IN
HOSPITALIZED INFANTS
Abstract
Background Nirsevimab, a novel monoclonal antibody, provides
passive immunity against RSV-infections in infants. In October/2023,
Spain adopted immunization for children <6 months and those born
during the epidemic season. Our main goal was to compare clinical,
epidemiological and virological characteristics of respiratory
infections in hospitalized infants before and after nirsevimab
introduction. Methods. A prospective study was conducted in two
Madrid hospitals during the 2022-23 and 2023-24 epidemic seasons.
Infants <12 months admitted with lower respiratory tract
infections were included. Clinical, epidemiological, and virological
characteristics were compared based on admission before or after
nirsevimab introduction and whether they received it. Results A
total of 717 infants were included: 526 before October/2023 and 191
thereafter. Admissions from October-March 2023/24 decreased by 59%
(95%CI:58.7-62.3%) compared to October-March 2022/23. ICU admissions
dropped by 74% (95%CI:70.7-77.3%). Of those hospitalized after
October/2023, 55(28.8%) received nirsevimab, with 11(20%) contracting
RSV. The RSV-detection rate was lower after October/2023 (39% vs. 65%,
P<0.001), as was the detection of other respiratory viruses,
except rhinovirus and human bocavirus. Patients admitted after
October/2023 were older (P=0.002), included fewer infants under 1 month
(P=0.005), and had shorter hospital stays (P=0.001). For infants under 3
months, the likelihood of needing a stay > 5 days was 70%
lower compared to those admitted before October/2023
(P<0.001;OR:0.39, 95%CI:0.22-0.66). Conclusions
Nirsevimab has shown considerable effectiveness in shielding young
infants from severe outcomes linked to RSV-infection. Furthermore, our
study observed a notable decrease in hospitalizations for infections
caused by other respiratory viruses after the introduction of
nirsevimab.