title: Letter: Efficacy of vaccines against influenze.
mesh_terms: D004196:Disease Outbreaks / Q000517:prevention & control*; D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000517:prevention & control*; D013019:South Africa; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines