Estimating the Burden of Influenza Hospitalizations Across Multiple Seasons Using Capture-Recapture

Influenza remains an important cause of hospitalizations in the United States. Estimating the number of influenza hospitalizations is vital for public health decision making. Combining existing surveillance systems through capture-recapture methods allows for more comprehensive burden estimations.

Data from independent surveillance systems were combined using capture-recapture methods to estimate influenza hospitalization rates for children and adults in Middle Tennessee during consecutive influenza seasons from 2016-2017 through 2019-2020. The Emerging Infections Program (EIP) identified cases through surveillance of laboratory results for hospitalized children and adults. The Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and New Vaccine Surveillance Network (NVSN) recruited hospitalized patients with respiratory symptoms or fever. Population-based influenza rates and the proportion of cases detected by each surveillance system were calculated.

Estimated overall influenza hospitalization rates ranged from 23 influenza-related hospitalizations per 10 000 persons in 2016-2017 to 40 per 10 000 persons in 2017-2018. Adults aged ≥65 years had the highest hospitalization rates across seasons and experienced a rate of 170 hospitalizations per 10 000 persons during the 2017-2018 season. EIP consistently identified a higher proportion of influenza cases for adults and children compared with HAIVEN and NVSN, respectively.

Current surveillance systems underestimate the influenza burden. Capture-recapture provides an alternative approach to use data from independent surveillance systems and complement population-based burden estimates.