Study Finds Self-reported Historical Influenza Vaccination Status Reliable in Most Health Care Personnel

Many studies of influenza vaccination among health care personnel (HCP) rely on self-reported vaccination status, but few have assessed the validity of self-reported past vaccination for multiple seasons.

To evaluate the validity of self-reported vaccination data, a study published in Influenza and Other Respiratory Viruses compared self-reported historical vaccination information to administrative vaccination records over the preceding 5 seasons.

HCP are a priority group for influenza vaccination given their potential for exposure to and transmission of influenza, and assessment of annual influenza vaccine effectiveness and coverage is crucial given this population’s high rates of vaccination.

"HCP are also a highly immunized population group. In the United States, as a result of employer-based mandates and other vaccine promotion initiatives following the 2009 H1N1 pandemic, many HCP receive the influenza vaccine annually and have a history of repeated vaccination," the authors explained.

Repeated vaccination also carries a risk of blunted immune response to influenza vaccines over time, meaning accurate recording of past vaccination status is an important aspect of studies in HCP.

The cross-sectional analysis included 683 HCP who took part in a multisite, randomized, open-label influenza vaccine immunogenicity trial during the 2018-2019 and 2019-2020 influenza seasons in the United States (NCT03722589). All had documented vaccination records available for 5 seasons prior to their enrollment in the trial that could be compared with reported past vaccination status.

Each patient’s reported vaccination status was verified with one or more administrative sources, including electronic medical records, employee health immunization records, medical information from vaccination providers such as pharmacies, health insurance claims, or state vaccination records.

Of the 683 HCPs in the study, most (89.7%) accurately self-reported their vaccination status from the season prior to the study survey. By the fifth season prior to the study, 82.6% of participants accurately reported their vaccination status. A total of 147 patients had information available for the sixth previous season, and 73.5% were able to self-report their status accurately. 

Participants who were able to consistently accurately self-report their vaccination status for the 5 preceding seasons were more likely to have been vaccinated for every season. Those who were only vaccinated for some of the preceding seasons (18.3%) more commonly had 2 or more errors in their self-reporting compared with those who were vaccinated for all 5 seasons (55.7% versus 4.2%, respectively). 

Overall, however, recall accuracy was high in the study cohort, particularly for the first season prior to survey.

“In the absence of available documentation such as electronic medical records or state immunization information system data, self-report is an acceptable method of data collection for studies aiming to measure historical exposure to influenza vaccines,” study authors wrote. “To minimize potential misclassification of vaccination status, especially in inconsistently vaccinated individuals, reliance on self-report should be restricted to one prior influenza season unless an annual vaccination mandate is in place.”

Reference

Regan AK, Wesley MG, Gaglani M, et al. Consistency of self-reported and documented historical influenza vaccination status of US healthcare workers. Influenza Other Respir Viruses. Published online April 12, 2022. doi:10.1111/irv.12988