The most effective means of controlling infectious bronchitis in poultry is by vaccination. Live attenuated vaccines based on the H120 strain (Mass serotype) are the most commonly used vaccines. Since vaccination is often performed in the hatchery, long duration of immunity is preferred. Avishield IB H120, a live attenuated vaccine based on the strain H120 is registered across the European Union and other countries, and has a declared immunity period of up to 5 weeks after vaccination. This study presents the results of an additional survey demonstrating protection against challenge with the IBV strain M41 up to 8 weeks after a single vaccination with Avishield IB H120. Seven weeks after vaccination, 94% of chickens vaccinated by spray were protected against the challenge. Eight weeks after vaccination, 80% of spray vaccinated chickens and 75% of orally vaccinated chickens were still protected against the challenge with virulent IBV.; Cijepljenje je najučinkovitiji način kontrole zaraznog bronhitisa u peradi. Najčešće korištena cjepiva su živa atenuirana cjepiva temeljena na soju H120 (pripadaju Mass serotipu). Budući da se cijepljenje često provodi već u valionici, poželjno je dugo trajanje imunosti. Avishield IB H120, živo atenuirano cjepivo koje sadrži cjepni soj H120, registrirano je u brojnim zemljama Europske unije i na drugim tržištima s deklariranim trajanjem imunosti od 5 tjedana nakon cijepljenja. U ovom radu prikazani su rezultati dodatne studije gdje smo dokazali zaštitu od izazivačke infekcije s patogenim virusom M41 i 8 tjedana nakon cijepljenja s Avishield IB H120 putem spreja ili vode za piće.