On temporal changes in the role of different age groups in propagating the Omicron epidemic waves in England

BackgroundThere is limited information on the role of individuals in different age groups in the spread of infection during the Omicron epidemics, especially ones beyond the winter epidemic wave in 2021-2022. COVID-19 booster vaccination in England during the Autumn 2022 was restricted to persons aged over 50y, and persons in clinical risk groups. MethodsWe used previously developed methodology to evaluate the role of individuals in different age groups in propagating the Spring, Summer, and Autumn waves of the Omicron epidemic in England. This methodology utilizes the relative risk (RR) statistic that measures the change in the proportion of cases in each age group among all COVID-19 cases in the population before the peak of an epidemic wave vs. after the peak of an epidemic wave. Higher values for the RR statistic represent age groups that experienced a disproportionate depletion of susceptible individuals during the ascent of the epidemic (due to increased contact rates and/or susceptibility to infection). ResultsFor the 2022 Spring wave, the highest RR estimate belonged to children aged 5-9y (RR=2.05 (95%CI (2.02,2.08)), followed by children aged 10-14y (RR=1.68 (1.66,1.7)) and children aged 0-4y (RR=1.38 (1.36,1.41)). For the Summer wave, the highest RR estimates belonged to persons aged 20-34y: (RR=1.09 (1.07,1.12) in aged 20-24y, RR=1.09 (1.07,1.11) in aged 25-29y, RR=1.09(1.07,1.11) in aged 30-34y). For the Autumn wave, the highest RR estimates belonged to those aged 70-74y (RR=1.10 (1.07,1.14)), followed by adults aged 35-39y (RR=1.09 (1.06,1.12)), adults aged 40-44y (RR=1.09 (1.06,1.12)), and adults aged 65-69y (RR=1.08 (1.05,1.11)). ConclusionsAs time progressed, the greatest relative roles in propagating different waves of the Omicron epidemic in England shifted from school-age children to younger adults to adults aged 35-44y and 65-74y. Extending booster vaccination to all adults, and possibly to children should help limit the spread of Omicron infections in the community.