Impact of the Coronavirus Disease 2019 Pandemic on the Clinical Features of Pediatric Respiratory Syncytial Virus Infection in Japan

The accumulation of susceptible children resulted in a resurgence of RSV, but the increase in hospitalized patients aged >= 2 years was modest. Our results suggest that the majority of primary RSV infections after infancy do not lead to severe symptoms. Background Mitigation measures implemented during the coronavirus disease 2019 (COVID-19) pandemic remarkably reduced the incidence of infectious diseases among children. However, a re-emergence of respiratory syncytial virus (RSV) infection was observed in 2021 in Japan. We compared the clinical characteristics of hospitalized patients with RSV infection before and during COVID-19. Methods We retrospectively enrolled children aged <6 years who were hospitalized with RSV infection in 18 hospitals and compared their clinical characteristics before (January 2019 to April 2020, 1675 patients) and during COVID-19 (September 2020 to December 2021, 1297 patients). Results The mean age of patients with RSV infection was significantly higher during COVID-19 than before (17.4 vs 13.7 months, P < .001). Compared with before COVID-19, a 2.6-fold increase in RSV cases in the 2-5 years age group was observed from sentinel surveillance during COVID-19, whereas a 1.2-fold increase was noted in the same age group among hospitalized patients. On average for all patients, consolidation shadows obtained on radiography were less frequently observed (26.1 vs 29.6%, P = .04), and reduced respiratory assistance (42.2% vs 48.7%, P < .001) and hospitalization stay (5.7 vs 6.0 days, P < .001) was required in patients with RSV infection during COVID-19. Conclusions Coronavirus disease 2019 and social activity restriction caused epidemiological changes in pediatric RSV infections, and a majority of patients with RSV infection aged >= 2 years did not develop severe symptoms requiring hospitalization. The RSV symptoms during the COVID-19 outbreak were equivalent to or milder than in the previous seasons.

Automated summary

The COVID-19 pandemic and social activity restriction led to epidemiological changes in pediatric RSV infections, with the majority of RSV-infected patients aged 2 years and above not developing severe symptoms. The symptoms of RSV during the COVID-19 outbreak were equivalent to or milder than in previous seasons.