Mass vaccination and additional health measures in 2009: a preliminary analysis of the effects on Indonesian Hajj pilgrims

Abstract

Background: The Hajj is an annual religious mass gathering of pilgrims from different countries in the Holy City of Mecca situated within the Kingdom of Saudi Arabia (KSA). Respiratory diseases are identified as a common occurrence among Hajj pilgrims in Indonesian, KSA, Australian and Iranian studies. Some of these respiratory diseases are attributable to influenza, tuberculosis, pneumococcal infections and other viruses (e.g. rhinovirus, coronavirus (exclusion of Middle East Respiratory Syndrome (MERS)). In 2009, the Indonesian hajj pilgrims were vaccinated due to an additional requirement by KSA Hajj Health authorities because of the 2009 H1N1 (swine flu) pandemic. In Indonesia, pilgrims are provided with government subsidies for a 40 day trip to Mecca. Additional measures were implemented by the KSA authorities. This preliminary analysis compares the effects of mass vaccination and additional health measures in 2009 against years where there was no heightened alert for influenza. Material/methods: Data was anonymized and extracted from 2004 to 2011 mortality data on Indonesian Hajj pilgrims. To make the data more homogenous, we have excluded years where stampedes, or unusual events (e.g. hotel collapse) with more than 50 deaths, had occurred. Furthermore 2006 was also the year which a new medical trial intervention was introduced. Hence to maintain homogeneity of the data, 2004 and 2006 was excluded. Two causes of death, diseases of the respiratory system (J00-J99) and certain infectious and parasitic diseases (A00-B99), were selected. This is in accordance to the broad International Classification of Diseases (currently ICD-10) coding due to limited resources in KSA to do a full autopsy. Regression modelling was used to estimate the effects of 2009 (where interventions against influenza were undertaken) against the years where there were minimal interventions. Results: A total of 813 cases died from respiratory causes and certain infectious/parasitic diseases. The mortality rate ranged from 49.2 per 100,000 (in 2009) to 71.7 per 100,000 (in 2005) for respiratory causes, and 0.97 (in 2008) to 11.2 (in 2010) as shown in Figure 1a. The pilgrims arrive at variable time points prior to the hajj date depending on the travel group which they are assigned to (Figure 1b). There is a strong evidence that additional precautions and mass vaccination in 2009 had some protective effect (IRR 0.76, p<0.05) against mortality resulting from respiratory causes and certain infectious diseases. Males (IRR 1.74, p<0.05) were at greater risk of dying from a respiratory related cause. Conclusions: This is a preliminary analysis modelling the effects of mass vaccination and additional health measures undertaken in a mass gathering. There are also other factors like advisory against travel due to co-morbidities, age and gender. Further models will be developed using additional individual data for risk modelling to improve pilgrim safety.