Low Rates of Co-Administration of Respiratory Vaccines Across the United States: Experiences from a Large Vaccination Ecosystem

Introduction: Giving more than one vaccine at a single visit is safe and is recommended by the Advisory Committee on Immunization Practices, but how often it happens in routine practice is not well described. We measured co-administration of influenza, COVID-19, and respiratory syncytial virus (RSV) vaccines where vaccine supply and on-site availability were consistent. Objective: To better characterize rates of co-administration and potential missed opportunities. Methods: We conducted a retrospective, cross-sectional analysis of records from a vaccine management platform serving more than 5000 clinics in 43 US states. Patients were age-eligible for at least one of the three vaccines, had a visit between 1 July 2023 and 30 April 2024, and received at least one. Those receiving two or more vaccines at one visit were compared with those receiving one using chi-squared tests. Multivariable logistic regression identified independent predictors of co-administration. Results: Of the 1,233,349 patients who received a respiratory vaccine, 50,582 active patients (4.1%) received two or more at the same visit. Rates were highest at health departments (13.4%), among Vaccines for Children (5.9%) and Medicaid (5.5%) beneficiaries, at the highest-volume clinics (5.2%), and among patients aged 51 to 64 years (5.0%). Influenza with COVID-19 accounted for 91.3% of co-administrations, influenza with RSV for 5.4%, and RSV with COVID-19 for 2.5%; 0.7% received all three. Cohorts differed by age, gender, insurance, clinic specialty, and clinic volume (all p < 0.0001). After multivariable adjustment, health department specialty remained the strongest independent predictor of co-administration with smaller independent associations for age, gender, insurance type, and clinic volume. Conclusions: Co-administration remained uncommon even where all three vaccines were stocked and available at the visit, so supply does not explain this shortfall. The settings and payer groups at either end of the range show where standing orders and visit prompts could recover missed opportunities.