Using Point of Care Testing to estimate influenza vaccine effectiveness in the English primary care sentinel surveillance network

Introduction Rapid Point of Care Testing (POCT) for influenza could be used to provide information on influenza vaccine effectiveness (IVE) as well as influencing clinical decision-making in primary care. Methods We undertook a test negative case control study to estimate the overall and age-specific (6 months-17 years, 18-64 years, >= 65 years old) IVE against medically attended POCT-confirmed influenza. The study took place over the winter of 2019-2020 and was nested within twelve general practices that are part of the Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC), the English sentinel surveillance network. Results 648 POCT were conducted. 193 (29.7%) of those who were swabbed had received the seasonal influenza vaccine. The crude unadjusted overall IVE was 46.1% (95% CI: 13.9-66.3). After adjusting for confounders the overall IVE was 26.0% (95% CI: 0-65.5). In total 211 patients were prescribed an antimicrobial after swab testing. Given a positive influenza POCT result, the odds ratio (OR) of receiving an antiviral was 21.1 (95%CI: 2.4-182.2, p = <0.01) and the OR of being prescribed an antibiotic was 0.6 (95%CI: 0.4-0.9, p = <0.01). Discussion Using influenza POCT in a primary care sentinel surveillance network to estimate IVE is feasible and provides comparable results to published IVE estimates. A further advantage is that near patient testing of influenza is associated with improvements in appropriate antiviral and antibiotic use. Larger, randomised studies are needed in primary care to see if these trends are still present and to explore their impact on outcomes.