COVID-19 and influenza vaccine co-administration among older U.S. adults.

INTRODUCTION: Co-administering COVID-19 and influenza vaccines is recommended by public health authorities and intended to improve uptake and convenience; however, the extent of vaccine co-administration is largely unknown. Investigations into COVID-19 and influenza vaccine co-administration are needed to describe compliance with newer recommendations and to identify potential gaps in the implementation of co-administration.

METHODS: A descriptive, repeated cross-sectional study between September 1, 2021 to November 30, 2021 (Period 1) and September 1, 2022 to November 30, 2022 (Period 2) was conducted. This study included community-dwelling Medicare beneficiaries ≥ 66 years who received an mRNA COVID-19 booster vaccine in Periods 1 and 2. The outcome was an influenza vaccine administered on the same day as the COVID-19 vaccine. Adjusted ORs and 99% CIs were estimated using logistic regression to describe the association between beneficiaries' characteristics and vaccine co-administration. Statistical analysis was performed in 2023.

RESULTS: Among beneficiaries who received a COVID-19 vaccine, 78.8% in Period 1 (N=6,292,777) and 89.1% in Period 2 (N=4,757,501), received influenza vaccine at some point during the study period (i.e., before, after, or on the same day as their COVID-19 vaccine), though rates were lower in non-White and rural individuals. Vaccine co-administration increased from 11.1% to 36.5% between periods. Beneficiaries with dementia (aORPeriod 2 =1.31; 99%CI=1.29-1.32) and in rural counties (aORPeriod 2 =1.19; 99%CI=1.17-1.20) were more likely to receive co-administered vaccines, while those with cancer (aORPeriod 2 =0.90; 99%CI=0.89-0.91) were less likely.

CONCLUSIONS: Among Medicare beneficiaries vaccinated against COVID-19, influenza vaccination was high, but co-administration of the two vaccines was low. Future work should explore which factors explain variation in the decision to receive co-administered vaccines.