Vaccinations against respiratory tract infections at Hajj

The transmission of respiratory tract infections (RTIs) is very high among the Hajj congregation in Mecca, Saudi Arabia. Despite recommendations for vaccinations, pilgrims remain at increased risk of RTIs. In this paper we systematically reviewed available studies assessing the uptake and effectiveness of vaccinations against RTIs among Hajj pilgrims and enumerated important demographic factors, if described, associated with vaccine uptake. Of the 42 included studies, 29 reported on the uptake and effectiveness of influenza vaccine among pilgrims, eight studies reported the uptake of other vaccines, notably pneumococcal, diphtheria and bacillus Calmette-Guérin vaccines, and the remaining five studies described both influenza and non-influenza vaccines. The uptake of seasonal influenza vaccine ranged from 0.7% to 100% across the study populations, with coverage highest in the elderly and those with pre-existing co-morbidities. The effectiveness of influenza vaccine was variable across studies but was significantly effective against laboratory-confirmed influenza (risk ratio 0.56; 95% CI 0.41-0.75; p <0.001) in pooled metadata from six studies. Uptake of diphtheria and pneumococcal vaccines was low, and the only study reporting pertussis among Hajj pilgrims found the presence of pre-Hajj immunity to be significantly protective against disease. Despite favourable evidence of effectiveness, our review shows variable uptake of vaccines across a number of studies with few data available on the uptake of non-influenza vaccines. Mixed-method studies are needed to gauge knowledge, attitudes and practices of Hajj pilgrims regarding vaccination, and randomized controlled trials are required to confirm the efficacy of vaccines and improve uptake in this vulnerable travelling population.