Safety, Immunogenicity, and Efficacy of a COVID-19 Vaccine (NVX-CoV2373) Co-administered With Seasonal Influenza Vaccines

Summary Background The safety and immunogenicity profile of COVID-19 vaccines when administered concomitantly with seasonal influenza vaccines has not yet been reported. Methods A sub-study on influenza vaccine co-administration was conducted as part of the phase 3 randomized trial of the safety and efficacy of NVX-CoV2373. The first ∼400 participants meeting main study entry criteria and with no contraindications to influenza vaccination were invited to join the sub-study. After randomization in a 1:1 ratio to receive NVX-CoV2373 (n=217) or placebo (n=214), sub-study participants received an age-appropriate, licensed, open-label influenza vaccine with dose 1 of NVX-CoV2373. Reactogenicity was evaluated via electronic diary for 7 days post-vaccination in addition to monitoring for unsolicited adverse events (AEs), medically-attended AEs (MAAEs), and serious AEs (SAEs). Influenza haemagglutination inhibition and SARS-CoV-2 anti-spike IgG assays were performed. Vaccine efficacy against PCR-confirmed, symptomatic COVID-19 was assessed. Comparisons were made between sub-study and main study participants. Findings Sub-study participants were younger, more racially diverse, and had fewer comorbid conditions than main study participants. Reactogenicity events more common in the co-administration group included tenderness (70.1% vs 57.6%) or pain (39.7% vs 29.3%) at injection site, fatigue (27.7% vs 19.4%), and muscle pain (28.3% vs 21.4%). Rates of unsolicited AEs, MAAEs, and SAEs were low and balanced between the two groups. Co-administration resulted in no change to influenza vaccine immune response, while a reduction in antibody responses to the NVX-CoV2373 vaccine was noted. Vaccine efficacy in the sub-study was 87.5% (95% CI: -0.2, 98.4) while efficacy in the main study was 89.8% (95% CI: 79.7, 95.5). Interpretation This is the first study to demonstrate the safety, immunogenicity, and efficacy profile of a COVID-19 vaccine when co-administered with seasonal influenza vaccines. The results suggest concomitant vaccination may be a viable immunisation strategy. Funding This study was funded by Novavax, Inc. Research in Context Evidence before this study We searched PubMed for research articles published from December 2019 until 1 April 2021 with no language restrictions for the terms “SARS-CoV-2”, “COVID-19”, “vaccine”, “co-administration”, and “immunogenicity”. There were no peer-reviewed publications describing the simultaneous use of any SARS-CoV-2 vaccine and another vaccine. Several vaccine manufacturers had recent publications on phase 3 trials results (Pfizer/BioNTech, Moderna, AstraZeneca, Janssen, and the Gamaleya Research Institute of Epidemiology and Microbiology). Neither these publications nor their clinical trials’ protocols (when publicly available) described co-administration and they often had trial criteria specifically excluding those with recent or planned vaccination with any licenced vaccine near or at the time of any study injection. Added value of this study Immune interference and safety are always a concern when two vaccines are administered at the same time. This is the first study to demonstrate the safety and immunogenicity profile and clinical vaccine efficacy of a COVID-19 vaccine when co-administered with a seasonal influenza vaccine. Implications of all the available evidence This study provides much needed information to help guide national immunisation policy decision making on the critical issue of concomitant use of COVID-19 vaccines with influenza vaccines.