3. Results
Between July 4, 2021, to December 26, 2021, 234,621 cases of confirmed COVID-19 were reported to the RJ State Health Department, with the Delta variant of concern being responsible for the majority of cases [2]. By November 7, 2021, COVID-19 cases had declined precipitously, coinciding with a rise in influenza cases (Figure 2). Cases of COVID-19 during this period accounted for 40,712 hospitalizations and 13,377 deaths, with a case fatality rate of 5,701 per 100,000 in the state during this time frame. An estimated 68,077 cases of influenza due to the H3N2 Darwin type A influenza strain [4] occurred between November to December 2021 [6], with an estimated case fatality rate of 1.3%. The circulating strain of H3N2 influenza virus was different from the H3N2 strain provided in the trivalent vaccine during the fall/winter period of 2021. Influenza vaccine coverage in the RJ state population during the spring/winter of 2021 was less than 60% [3].