Placebo-controlled double-blind clinical studies on the efficacy of different influenza vaccines assessed by experimental and natural infection.
D002986:Clinical Trials as Topic; D005069:Evaluation Studies as Topic; D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000517:prevention & control*; D010919:Placebos; D014613:Vaccines, Attenuated
D007252:Influenza Vaccines; D010919:Placebos; D014613:Vaccines, Attenuated