Age-specific hospitalization risk of primary and secondary respiratory syncytial virus infection among young children

Objectives: Elucidating the infection dynamics that lead to severe respiratory syncytial virus (RSV) pneumonia and hospitalization among young children are critical. We explored the role of infection parity as well as age in months for RSV-associated hospitalization among young children in Japan. Methods: We used a sequential transmission catalytic model to capture the transmission mechanisms of RSV among infants in an endemic state. We investigated data on the age-dependent seroprevalence and incidence rate of hospitalization in Japan, and jointly estimated the age-specific risk of hospitalization during primary RSV infection and relative risk of hospitalization during secondary infection in children aged <5 years. Results: The estimated risk of hospitalization with primary infection was 0.08 (95% CI: 0.05-0.14) in infants aged 0-2 months. The estimated relative risk of hospitalization owing to secondary infection was 0.18 (95% CI: 0.01-2.04). Conclusion: Our simple models successfully captured the infection dynamics of RSV among young children in Japan. The age group of early infancy may be most vulnerable to infection and hospitalization, offering key insights into future vaccinations. The burden of hospitalization from secondary infection may be less important in young children. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.

Automated summary

This study aimed to elucidate the infection dynamics that lead to severe respiratory syncytial virus (RSV) pneumonia and hospitalization among young children. The research found that the risk of hospitalization with primary infection was higher in infants aged 0-2 months, and the relative risk of hospitalization due to secondary infection was relatively low in young children.