[EPIDEMIOLOGICAL VERIFICATION OF THE EFFECTIVENESS OF LIVE INFLUENZA VACCINE].
D002031:Bulgaria; D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human; D014613:Vaccines, Attenuated
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated
BULGARIA; INFLUENZA VACCINE
EPIDEMIOLOGICHESKAIA PROVERKA 'EFFEKTIVNOSTI ZHIVO I PROTIVOGRIPPOZNO I VAKTSINY.