The effect of pharmacists as vaccinators on uptake of influenza vaccination in Denmark: An interrupted time series analysis

BACKGROUND: Pharmacists increasingly serve as vaccinators for routine and seasonal vaccines. However, research is scarce regarding the effect of policies supporting pharmacist-administered vaccination on uptake of influenza vaccines. OBJECTIVE: To assess the impact of pharmacist-administered vaccination on vaccination coverage rates (VCRs) for seasonal influenza in older adults in Denmark. METHODS: Using national vaccine surveillance data, annual influenza VCRs among older adults (≥65 years) were evaluated in an interrupted time series model, with 2009-2014 as the baseline period (pre-pharmacist vaccination policies), 2015 as the interruption event (policy change), and 2016-2019 as the post-interruption period (pharmacists authorized to vaccinate). Confounding by secular trends was evaluated in sensitivity analyses using VCRs for influenza in younger individuals (15-64 years) and routine childhood vaccines as comparators. RESULTS: The influenza VCR in older adults, 49.8% in 2009, decreased by .73 mean percentage points (mpp) yearly through 2014 and did not significantly change in 2015. From 2015 through 2019 the VCR increased by 2.13 mpp yearly, corresponding to a 2.86 mpp yearly increase above the baseline trend (95% CI: 1.82, 3.90; P < .001) during the post-interruption period. Post-interruption annual increases in the VCR were significantly higher than estimates from the sensitivity cohorts, suggesting minimal confounding by secular trends. CONCLUSIONS: A mean annual increase in influenza VCRs among older adults of nearly 3 percentage points after authorization of pharmacist-implemented vaccination compared with the pre-policy period demonstrates that pharmacist-administered vaccination may support vaccine uptake among older adults.