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Vaccination campaign before Hajj appears to have protected pilgrims from 2009 pandemic flu

Kandeel A. Emerg Infect Dis. 2011;17(7):in press.
Posted on the Pediatric SuperSite on June 16, 2011

The 2009 pandemic influenza vaccine given to Egyptian pilgrims before their journey to the Hajj appeared to protect them from the pandemic virus.

The annual pilgrimage to Mecca and Medina, Saudi Arabia, for the Hajj occurred at the height of the 2009 H1N1 influenza pandemic. Therefore, the Egyptian Ministry of Health implemented a mandatory pre-departure vaccination with pandemic influenza vaccine to protect its residents from influenza during their trip and to prevent them from importing the virus into country upon their return. Approximately 80,000 Egyptians make the trip each year, according to a new study from the CDC.

Results of a survey sample of Egyptian pilgrims returning from the Hajj indicate that the pandemic vaccination campaign was significantly effective. The survey, conducted during the peak return period, included passengers arriving at Cairo International Airport from Dec. 10 to Dec. 12 from nine separate flights that originated in Jeddah. Passengers on a ship from Jeddah arriving at Port Tawfik were also included in the survey.

The epidemiologists, health workers and laboratory technicians selected pilgrims without regard to age, sex or illness status and managed to survey about 50 passengers from each flight. Every 10th pilgrim was selected as they disembarked the ship. The age of survey participants ranged from 12 to 65 years.

A total of 551 pilgrims had oropharyngeal samples taken and tested at the US Naval Medical Research Unit in Cairo by real-time reverse-transcription polymerase chain reaction. All but nine pilgrims tested had received the required pre-travel pandemic influenza vaccine.

Only six pilgrims (1%) tested positive for influenza A, all of whom had subtype H3N2; testing for influenza B was not performed. None of the pilgrims returning from the Hajj tested positive for the 2009 pandemic influenza A (H1N1) virus, according to the study findings.

At the time of the Hajj, the 2009 pandemic influenza (H1N1) virus was the most common circulating virus in the Northern and Southern hemispheres, and few countries implemented a pre-departure vaccination program. Therefore, the researchers said pilgrims were likely exposed during the Hajj and the vaccine provided protection, but further study is needed.

Study limitations include: 1) the results may not apply to pilgrims who returned to Egypt before or after the survey period; 2) some areas of Egypt were under-represented in the sample; 3) convenience sampling was used to select pilgrims arriving by plane; 4) unvaccinated pilgrims may have been reluctant to tell interviewers of their status; and 5) some pilgrims may have been infected with pandemic virus shortly before swab samples were obtained and were not yet shedding virus.