Influenza Cases and Vaccination During the COVID-19 Pandemic in Puerto Rico

Background: Influenza and COVID-19 share some similarities in transmission, and decreasing annual incidence of influenza during the pandemic has been reported.Objective: To evaluate the distribution of influenza cases in Puerto Rico (PR) during the pandemic, and related factors including sociodemograhic factors, influenza vaccination, and public health social measures (PHSM).Methods: The Puerto Rico Epidemiological evaluation and Prevention of COVID-19 and Influenza (PREPCOVI) study invited adults ≥ 21 years from across PR to participate in a brief online survey. Participants were recruited through automated text messages to random phone numbers from November 18, 2020 through June 24, 2021.Results: Of the 6,960 participants, 13.4% reported testing for influenza in the last 30 days (males: 14.8%, females: 12.6%). At least 75% of participants practiced one or more PHSM, regardless of influenza status. Influenza incidence over the study period was 0.7%. Test positivity in the last 30 days was 5.3%, higher among females (6.2%), and among the 40-64 age group (5.8%). Among the 58.5% vaccinated for influenza, 59.2% were last vaccinated between 2020-2021; their test positivity was 3.5%, compared to 6.1% among never vaccinated or 7.1% among participants vaccinated before 2020. PR Department of Health data shows reduced influenza incidence during the pandemic.Conclusion: Influenza incidence and test positivity were low when most people in PR were following PHSM to prevent COVID-19. Among participants vaccinated during 2020-2021, there was lower test positivity compared to participants with earlier or no influenza vaccination. Vaccination and PHSM may be important in preventing influenza.