LONDON – It is both safe and effective for people to receive an influenza vaccine at the same time as a COVID-19 vaccine, with no negative impacts on the strength of the immune response produced by either vaccine and reported side effects mainly mild to moderate. Only nine of 679 participants in a U.K. study testing combinations of different flu and COVID-19 vaccines said they would not want to have two different vaccines at the same time in the future. Six of those were in the control arm of the trial, in which saline was injected as a placebo.