Co-administration of COVID-19 and flu vaccines in healthcare workers: results from three campaigns

Abstract The COVID-19 pandemic, along with seasonal influenza, highlights the need for innovative public health strategies. Co-administering COVID-19 and influenza vaccines offers advantages for healthcare workers (HCWs), streamlining vaccination efforts and enhancing public health resilience. Recent evidence supports the safety and efficacy of this approach, endorsed by health authorities worldwide. However, its acceptance remains a concern. This study explores HCWs’ acceptance of vaccine co-administration in three campaigns post the introduction of the anti-SARS-CoV-2 vaccine. During three consecutive flu seasons from October 2021 to January 2024, a cross-sectional study was conducted in a large Italian teaching hospital. Data for 2021/2022, 2022/2023 and 2023/2024 were compared, focusing on healthcare workers present in all datasets. McNemar’s test examined changes in acceptance of co-administration. In addition, a conditional logistic regression model was designed to assess the determinants of co-administration through the vaccination campaigns in the three years. During these vaccination campaigns 7457 HCWs were observed (62.78% women, median age 43). Co-administration surged, particularly in 2022/2023, showing a 280.71% increase, consistent across all professional categories (p < 0.001). Controlling for gender and professional category, acceptance of coadministration showed a significant association respectively with “open days” twice a month (OR 2.9 CI [2.7; 3.6]) and a hospital vaccination clinic two days a week on weekdays (OR 4.5 CI [4.1; 5.4]) compared to conducting vaccinations at a clinic open everyday during the campaign period; no association was highlighted with age. This study investigates a facet of an increasingly significant topic, demonstrating that co-administering vaccines for SARS-CoV-2 and influenza is emerging as an effective strategy in annual vaccination campaigns, thanks to its safety and the streamlining of logistical and organizational processes. Key messages • The co-administration of vaccines offers a promising strategy to enhance vaccination rates among healthcare workers. • By identifying factors influencing acceptance, it aims to inform targeted interventions for maximizing vaccine uptake and public health resilience.