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Objectives: We aimed to study whether the percentwise age distribution of RSV cases changes over time during annual epidemics., Methods: We used surveillance data (2008-2019) from the Netherlands, Lyon (France), Portugal, Singapore, Ecuador, South Africa, and New Zealand. In each country, every season was divided into "epidemic quarters", i.e. periods corresponding to each quartile of RSV cases. Multinomial logistic regression models were fitted to evaluate whether the likelihood of RSV cases being aged <1 or ≥5 years (vs. 1 to <5) changed over time within a season., Results: In all countries, RSV cases were significantly more likely to be aged <1 year in the 4th vs. 1st epidemic quarter; the relative risk ratio [RRR] ranged between 1.35 and 2.56. Likewise, RSV cases were significantly more likely to be aged ≥5 years in the 4th vs. 1st epidemic quarter (except in Singapore); the RRR ranged from 1.75 to 6.70. The results did not change when stratifying by level of care or moving the lower cut-off to 6 months., Conclusions: The age profile of RSV cases shifts within a season, with infants and adolescents, adults, and the elderly constituting a higher proportion of cases in the later phases of annual epidemics. These findings may have implications for RSV prevention policies with newly approved vaccines., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: M.B. and R.K. are Sanofi employees and may hold shares and/or stock options in the company. J.P. reports that Nivel has received RSV research grants from the Foundation for Influenza Epidemiology and Sanofi. The remaining authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)