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

Abstract

Background: There 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. Methods: We 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). Results: For the 2022 Spring wave, the highest RR estimate belonged to children aged 5 to 9y (RR=2.05 (95%CI (2.02,2.08)), followed by children aged 10 to 14y (RR=1.68 (1.66,1.7)) and children aged 0 to 4y (RR=1.38 (1.36,1.41)). For the Summer wave, the highest RR estimates belonged to persons aged 20 to 34y: (RR=1.09 (1.07,1.12) in aged 20 to 24y, RR=1.09 (1.07,1.11) in aged 25 to 29y, RR=1.09(1.07,1.11) in aged 30 to 34y). For the Autumn wave, the highest RR estimates belonged to those aged 70 to 74y (RR=1.10 (1.07,1.14)), followed by adults aged 35 to 39y (RR=1.09 (1.06,1.12)), adults aged 40 to 44y (RR=1.09 (1.06,1.12)), and adults aged 65 to 69y (RR=1.08 (1.05,1.11)). Conclusions: As 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 to 44y and 65 to 74y. Extending booster vaccination to all adults, and possibly to children should help limit the spread of Omicron infections in the community.

On the changing role of individuals in different age groups in propagating the Omicron epidemic waves in France

“…The role of individuals in different age groups during the subsequent waves of Omicron epidemics is less studied. In our companion paper [9], we showed that as time progressed, the leading relative role in propagating the Omicron epidemic waves in England shifted from school-age children to younger adults to adults aged 35-44y and 65-74y. In this paper, we applied the previously developed methodology [14-16,3,4] to study the relative role of individuals in different age groups during the Spring, Summer, Autumn and Autumn-Winter waves of the 2022 Omicron epidemic in France.…”

“…This method was also used in the context of SARS-CoV-2 epidemics in 2020 and 2021 to show the prominent relative role of younger adults and older adolescents in the transmission process [4,5]. In our companion paper [9], we showed that as time progressed, the leading relative role in propagating the Omicron epidemic waves in England shifter from school-age children to younger adults to adults aged 35-44y and 65-74y. In this paper we use the RR statistic to examine the role of individuals in different age groups during four waves of the Omicron epidemic in France between March 1, 2022 and Dec. 29, 2022.…”

“…The role of different age groups during subsequent waves of Omicron epidemics needs a better characterization (e.g. see the Coronavirus Infection Surveys in the UK [8], as well as [9]). Such information could inform effort of booster vaccination, as well as other mitigation efforts aimed at limiting the spread of Omicron infection in the community.…”

“…This method was also used in the context of SARS-CoV-2 epidemics in 2020 and 2021 to show the prominent relative role of younger adults and older adolescents in the transmission process [4,5]. In our companion paper [9]…”

“…During the circulation of earlier SARS-CoV-2 variants, the leading role in the acquisition and spread of infection process generally belonged to younger adults (aged 18-35y) and older adolescents [7-10] – in particular, see the temporal data on the prevalence of SARS-CoV-2 infection in different age groups in England in [10]. The appearance of the Omicron variant resulted in a greater role of children in the transmission process, at least during the early stages of the Omicron epidemic [11]. For example, findings from REACT-1 study in England for samples tested between January 5-20, 2022 saw the greatest prevalence of infection in children aged 5-11y [12] (which is different from what was observed for the earlier SARS-CoV-2 variants [10]).…”