ABSTRACT
Background: Concomitant administration of COVID-19 and influenza vaccines would reduce burden on healthcare systems. We assess the safety of concomitant administration. Methods: Adults in receipt of a single dose of ChAdOx1 or BNT162b2 were enrolled at 12 UK sites and randomised 1:1 to receive concomitant administration of either age-appropriate influenza or placebo alongside second COVID-19 vaccine. Three weeks later the group who received placebo received the influenza vaccine, and vice versa. Participants were followed to six weeks. The influenza vaccines were three seasonal, inactivated vaccines (trivalent, MF59C adjuvanted (aTIV) or a cellular or recombinant quadrivalent vaccine (QIVc/QIVr)). Participants and investigators were masked to the allocation. The primary endpoint was one or more participant-reported solicited systemic reaction in the seven days after first trial vaccination(s), with a difference of <25% considered non-inferior. Local and unsolicited systemic reactions and humoral responses were also assessed (ISRCTN14391248). Findings: Between 1st April and 26th June 2021, 679 participants were recruited to one of six cohorts: (129 ChAdOx1/QIVc; 139 BNT162b2/QIVc; 146 ChAdOx1/aTIV; 79 BNT162b2/aTIV; 128 ChAdOx1/QIVr; 58 BNT162b2/QIVr). Overall, 340 participants were randomised to concomitant administration of influenza and COVID-19 vaccine and 339 were randomised to placebo and COVID-19 vaccine. Non-inferiority was indicated in four cohorts; ChAdOx1/QIVc: risk difference (influenza vaccine minus placebo) -1·29% (95% confidence interval (CI) ‑14·7%, 12·1%); BNT162b2/QIVc: 6·17% (‑6·27%, 18·6%); BNT162b2/aTIV: -12·9% (‑34·2%, 8·37%); ChAdOx1/QIVr: 2·53% (‑13·3%, 18·3%). In two cohorts the upper limit of the 95%CI exceeded 25%; ChAdOx1/aTIV: 10·3% (‑5·44%, 26·0%) and BNT162b2/QIVr: 6·75% (‑11·8%, 25·3%). Most reactions were mild or moderate. Rates of local and unsolicited systemic reactions were similar between randomised groups. One serious adverse event, hospitalisation with severe headache, was considered related to the trial intervention. Immune responses were not adversely affected. Interpretation: Concomitant vaccination raises no safety concerns and preserves the immune response to both vaccines.Clinical Trial Registration Details: The trial is registered (ISRCTN14391248)Funding Information: The trial is commissioned and funded by the Department of Health and Social Care (DHSC) through the National Institute for Health Research (NIHR). This research was supported by the Vaccine Task Force (VTF) and NIHR Policy Research Programme (PR-R17-0916-22001, NIHR203243).Declaration of Interest: RL reports grants from National Institute for Health Research during the conduct of the trial, and grants from Elizabeth Blackwell Institute, AstraZeneca, Janssen and Valneva outside the submitted work. CR reports grants from National Institute for Health Research, during the conduct of the trial. JSN-V-T reports he is seconded to the Department of Health and Social Care, England. AF reports grants from Pfizer during the conduct of the trial, and grants from Elizabeth Blackwell Institute, Gates Foundation, Sanofi Pasteur, VBI Vaccines, Pfizer, Janssen, GSK, MedImmune, Novavax and Valneva outside the submitted work. Between May 2015 and May 2019 AF was President of the European Society for Paediatric Infectious Diseases which, during this period, received sponsorship from GSK for its annual congress. He currently serves as chief investigator on the Valneva (Covid-19) vaccine phase 1/2 and 2/3 studies .He also serves as co-investigator on the Janssen (Covid-19) vaccine 2 dose phase 3 study. He does advisory work related to vaccines for the UK government, the World Health Organisation and several companies developing vaccines. He also leads clinical trials of vaccines funded by the UK government, charities and vaccine manufacturers. He receives no personal remuneration or benefits in kind for any of this work apart from his salary via the University of Bristol from the Higher Education Funding Council and the NHS. He is a member of the UK Department of Health’s Joint Committee on Vaccination, Chair of the WHO European Technical Advisory Group of Experts in which capacity he attends SAGE. AM reports grants from National Institute for Health Research during the conduct of the trial, and grants from AstraZeneca, Janssen and Valneva outside the submitted work. MDS acts on behalf of the University of Oxford as an investigator on studies funded or sponsored by vaccine manufacturers, including AstraZeneca, GlaxoSmithKline, Pfizer, Novavax, Pfizer, Janssen, Medimmune and MCM. The views in this paper are those of its authors and not necessarily those of the DHSC.Ethical Approval Statement: Approvals were received from the Medicines and Healthcare products Regulatory Agency (MHRA) (EudraCT number 2021-001124-18) and the South-Central Berkshire Research Ethics Committee (21/SC/0100).