On the role of different age groups in propagating Omicron epidemics in France

ObjectivesIn late December 2022, rates of mortality in France (over 2,500 daily deaths) have reached levels not seen since April 2020, with the most pronounced increase in mortality recorded in nursing homes. Epidemics of Omicron and influenza have both contributed to those high mortality levels in late 2022. The roles of different age groups in propagating Omicron epidemics in the whole community require a better characterization, particularly given that in France, vaccination coverage for the 2nd booster for COVID-19 is limited and largely restricted to persons aged over 60y. Patients and MethodsWe examined the role of individuals in different age groups in propagating different waves of Omicron epidemics in France between March 1--Dec. 30, 2022 using previously developed methodology based on the relative risk (RR) statistic that measures the change in the groups proportion among all cases 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 epidemics ascent (due to increased contact rates and/or susceptibility to infection). ResultsFor the Spring wave (March 14 - May 15), the highest RR estimate belonged to children aged 10-19y (RR=1.92 (95% CI (1.18,3.12)), followed by adults aged 40-49y (RR=1.45 (1.09,1.93)) and children aged 0-9y (RR=1.31 (0.98,1.74)). For the Summer wave (June 27 - Aug. 21), the highest RR estimate belong to children aged 0-9y (RR=1.61 (1.13,2.30)) followed by children aged 10-19y (RR=1.59 (0.77,3.26)) and adults aged 20-29y (RR=1.42 (0.91,2.23)). For the Autumn wave (Sep. 18 - Nov. 12), the highest RR estimate belonged to children aged 10-19y (RR=1.65 (0.72,3.75)), followed by adults aged 30-39y (RR=1.39 (0.83,2.33)) and 20-29y (RR=1.21 (0.66,2.23)). For the Autumn-Winter Wave (Nov. 23 - Dec. 30), the highest RR estimate belonged to persons aged 30-39y (RR=1.43 (0.79,2.57)), followed by persons aged 80-89y (RR= 1.17 (0.99,1.4)) and persons aged 40-49y (RR= 1.15 (0.73,1.82))). Discussion/ConclusionsIncreasing booster vaccination coverage for all adults, as possibly for children should help mitigate future Omicron epidemics. The estimate for the RR statistic in persons aged 80-89y for the Autumn-Winter Omicron wave suggests that additional efforts should be considered for preventing the spread of Omicron infection in elderly persons, including in Long-Term Care facilities.