Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

James Hadler


Since the COVID pandemic began in March 2020, the epidemiology of influenza has changeddramatically in the United States. During the 2021-2022 influenza season in Connecticut, only 262 hospitalized influenza cases were recorded in New Haven and Middlesex Counties from October 2021-June 2022, while there are usually well over 1,000 cases in a single season. While the decline in influenza cases could be due to preventive measures adopted early in the pandemic, viral interference could also be to blame. Viral interference is the process by which infection with one virus transiently protects against infection by another virus via a generalized immune response. Numerous studies have provided evidence supporting this phenomenon in respiratory viruses. To date, however, no studies have investigated this at the population level in Connecticut. The aim of the current study was to investigate whether there was evidence of viral interference between influenza and SARS-CoV-2 during the 2021-2022 influenza season in Connecticut using demographic data collected from hospitalized influenza and COVID cases from the Connecticut Emerging Infections Program at Yale. To do so, chi-square tests comparing the proportion of hospitalized COVID and influenza cases in different demographic groups were performed both within and between three distinct time periods of the 2021-2022 flu season before, during and after the first Omicron wave from December 2021-January 2022. Overall, the results of the chi-square tests did not show strong evidence for viral interference within or between the time periods studied. The percentage of COVID and flu cases in each demographic group changed in similar directions for most groups over time. While this study did not find evidence of viral interference, the number of influenza and COVID cases may not have been high enough to see evidence of this at the population level. Future studies are needed to investigate the level of infection that is needed in the population to see evidence of viral interference if it does in fact occur.


This is an Open Access Thesis.

Open Access

This Article is Open Access