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

Abstract

Background: There is limited information on the role of different age groups in propagating SARSCoV2 epidemics driven by the Omicron variants. Methods: We examined the role of individuals in different age groups in propagating the Spring, Summer, and Autumn waves of the Omicron epidemics in France using the previously developed methodology based on the relative risk (RR) statistic that measures the change in the proportion of an age group among all cases admitted to ICU for COVID19 before vs. after the peak of an epidemic wave. Higher value of the RR statistic for a given age group suggests a disproportionate depletion of susceptible individuals in that age group during the ascent of the epidemic (due to increased contact rates and/or susceptibility to infection). Results: For the Spring wave (March 14 through May 15), the highest RR estimate belonged to children aged 10 to 19y (RR=1.92 (95% CI (1.18,3.12)), followed by adults aged 40 to 49y (RR=1.45 (1.09,1.93)) and children aged 0 to 9y (RR=1.31 (0.98,1.74)). For the Summer wave (June 27 through Aug. 21), the highest RR estimate belonged to children aged 0 to 9y (RR=1.61 (1.12,2.3)) followed by children aged 10 to 19y (RR=1.46 (0.72,2.93)) and adults aged 20 to 29y (RR=1.42 (0.91,2.23)). For the Autumn wave (Sep. 18 through Nov. 12), the highest RR estimate belonged to children aged 10 to 19y (RR=1.63 (0.72,3.71)), followed by adults aged 30 to 34y (RR=1.34 (0.8,2.25)) and 20 to 24y (RR=1.20 (0.65,2.21)). Conclusions: Children aged 10 to 19y played the greatest relative role in propagating Omicron epidemics, particularly when schools were open, followed by children aged 0 to 9y and adults aged 20 to 29y, as well as adults aged 30 to 49y. Persons aged over 50y played a more limited role in propagating Omicron infection in the community. Additional efforts are needed to increase vaccination coverage in children aged 10 to 19y, as well as younger children and young adults to mitigate Omicron epidemics in the community.

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

“…For the Spring epidemic wave, we found a disproportionate depletion of susceptible individuals during the ascent period of the epidemic in children aged 5-14y, followed by children aged 0-4y and 15-19y. This result is generally in agreement with the findings in our study of Omicron epidemics in France [14], as well as with the high rates/earlier peaks of infection in children in England in the UK coronavirus survey data for that period [9]. We also note that several studies ([26-28]) suggest significant spread of SARS-CoV-2 infection in the school setting under limited mitigation of transmission (which generally applies to the Omicron period compared to the circulation of the earlier SARS-CoV-2 variants).…”

“…For the Spring epidemic wave, we found a disproportionate depletion of susceptible individuals during the ascent period of the epidemic in children aged 5-14y, followed by children aged 0-4y and 15-19y. This result is generally in agreement with the findings in our study of Omicron epidemics in France [14], as well as with the high rates/earlier peaks of infection in children in England in the UK coronavirus survey data for that period [9]. We also note that several studies ( [26][27][28])…”

“…However, studies of SARS-CoV-2 viral shedding suggest that viral shedding is quite prolonged, and its duration is positively correlated with age [12][13]. Therefore, percentage of people testing positive for coronavirus [9][10][11] overestimates the [14]. However, the relative role of children in the spread of Omicron infections in France declined during the Autumn wave of the 2022 epidemic compared to the earlier waves [14], and the relative role of children might be even smaller in places that experienced higher rates of infection in children earlier on.…”

“…We applied this method to data from SARS-CoV-2 epidemics in 2020 and 2021 [3,4] to show that younger adults and older adolescents had the greatest relative role in the spread of infection in the corresponding locations. We also applied this method to the Spring, Summer and Fall waves of the Omicron epidemic in France [14] and found that the greatest relative role in the spread of . CC-BY-NC 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.…”

“…Therefore, percentage of people testing positive for coronavirus [9-11] overestimates the rate of incidence of recent infection in different age groups, particularly for older persons. Our study of the Spring, Summer and Autumn Omicron epidemics in France suggests the importance of children and younger adults in the spread of Omicron infections [14]. However, the relative role of children in the spread of Omicron infections in France declined during the Autumn wave of the 2022 epidemic compared to the earlier waves [14], and the relative role of children might be even smaller in places that experienced higher rates of infection in children earlier on.…”