How Does Prior Influenza Vaccination Predict the Likelihood of Later Vaccinations for Influenza, COVID-19?

Individuals who previously utilized preventative services and immunizations for influenza were more likely to receive subsequent vaccinations for both influenza and COVID-19, according to the results of a study presented at IDWeek 2023.

Open and closed administrative claims were used to identify more than 3 million US adults who had evidence of an influenza vaccination administered from August 2020 through July 2021. All participants were insured and were followed up until subsequent influenza and/or COVID-19 vaccination, or the end of the study period (July 31, 2022).

Of the included participants, 13.7% received a subsequent influenza vaccination while 21.1% received a COVID-19 vaccination. Over half of all participants (50.7%) received both vaccines. The median time to a subsequent vaccine following the initial vaccine date was 373 days for influenza and 185 days for COVID-19. Of those who received both vaccines, 64.1% received the COVID-19 vaccine first.

Further, later receipt of both vaccines vs influenza alone was associated with prior influenza vaccination (Odds Ratio [OR] = 1.18; 95% CI, 1.18 to 1.19). Adults aged 65 years or older and others at high-risk for serious adverse events were slightly less likely to receive both vaccines vs influenza alone (≥65 years OR = 0.93; 95% CI, 0.92 to 0.94; high-risk OR = 0.91; 95% CI, 0.90 to 0.92).

However, the authors note that outcome misclassification may have impacted results, as data from as mass vaccination sites or patient populations with Medicare Advantage insurance were not included.

“As the pandemic subsides, there will be a continued need to assess COVID-19 and influenza vaccination patterns to inform future vaccination campaigns, including combination influenza and COVID-19 vaccines,” the researchers concluded.