The Hajj is an annual Muslim pilgrimage that begins on the first day of Dul-Hajja (12^th lunar month) and continues for 13 days. The Hajj occurs at the holy city of Mecca in the Kingdom of Saudi Arabia (KSA). The two- to three-million people who gather in the small, confined holy sites of the city come from multiethnic Muslim communities around the world [1–3].

The Saudi National Guard is a military and security force that includes several sub-administrations, of which one is the National Guard Health Affairs. This group is charged with providing health care services to National Guard personnel and their dependents. The group also offers medical services as necessary during the Hajj and other similar situations involving large groups of people.

Influenza pandemics are significant health threats that have occurred periodically over the past 300 years [4]. The most severe influenza pandemic, occurring from 1918 to 1919, killed approximately 30 to 50 million people worldwide. The emergence of the H5N1 avian influenza in 1997 promoted the recognition of the threat of another severe pandemic as a significant possibility, and such a pandemic would certainly be a threat at large gatherings such as the annual Hajj [5]. In response to this emerging threat, large-scale mitigation strategies have been developed. One cornerstone of these efforts is mass vaccination [6]. The current H1N1 pandemic, which was first recognized and defined in Mexico City in February 2009, spread rapidly throughout the world. Before the current Hajj season of 2009, the WHO declared there have been more than 300,000 laboratory confirmed cases of pandemic influenza H1N1 and 3,917 deaths in 191 countries [7].

In the current study, we assessed the acceptance of the H1N1 vaccination. We also examined possible barriers to vaccination within this high-risk cohort of employees, including both HCWs and non-HCWs, who worked at one of the largest human gatherings in the world.

In 2009, the large gathering of the annual pilgrimage (known as the Hajj) occurred concomitantly with the swine flu pandemic and the global panic surrounding the possibility of a rapid outbreak. For these reasons, we were interested in studying high-risk participants who were assigned to provide services during the pilgrimage. This allowed us to gather information about their attitudes toward the H1N1 vaccine. We were also interested in identifying and assessing the short-term adverse effects of the newly manufactured vaccine [10]. Regarding the current pandemic, the WHO had recommended that all countries give high priority to immunizing their HCWs to protect the essential health infrastructure. Despite these recommendations, the acceptance of voluntary vaccination was unexpectedly low [11].

This study explored reasons for swine flu vaccination refusal during a time of global public concern and anticipation of a global outbreak. In our cohort of Saudi National Guard employees assigned to work during the Hajj, 46.8% of participants accepted the vaccination. We found that more non-HCWs (mainly military personnel) accepted the vaccine than HCWs. This was consistent with our previously published finding that physicians had a low acceptance rate for both seasonal and pandemic vaccinations in early 2009/2010 [12].

Despite strong recommendations to vaccinate healthcare workers with the influenza vaccine, coverage was exceedingly low for all specialties, with some differences according to location and type of employment [13]. In addition to education about preventive measures, such as frequent hand washing and wearing a mask, vaccination is an essential protective measure. Influenza vaccination among healthy working adults has been shown to be highly effective, resulting in a 25% reduction of upper respiratory illness [14]. In this study, the reasons for refusal included worries about vaccination safety and doubts about vaccine efficacy. In a study from Hong Kong, the influenza vaccine was efficient in preventing H1N1 infection in 61% of the participants [15]. In addition, some participants believed that other preventive measures could be applied to yield the same benefits; misleading information from the media may have been the source of this reasoning. One of the prominent sources of concern was the difference in chemical constituents between the vaccine used in developed countries and those used in developing countries including the Kingdom. Participants' hesitance, worry, and safety concerns about using a newly developed vaccine were other major determinants of negative response and vaccination refusal. The most common reasons for accepting the vaccination were a "wish to be protected" and "following health authority advice." The most common reason for refusal was "worry about side effects." In addition, some other reasons for refusing vaccination included "doubts about the efficacy of the vaccine," feeling that it was "not yet the right time to be vaccinated," and "simply not wanting the vaccine [15]." Vaccine-seeking consumers must first be convinced of a reasonable likelihood that the disease will occur in their location and that they are susceptible. Additionally, they must be convinced that the disease is serious. Finally, they must be convinced of the safety, if not the efficacy, of the vaccine before they will accept it [15]. In a recent study conducted on a group of Saudi civilians, we were able to confirm that the media played a major role in decreasing the acceptance of the vaccine. Furthermore, the lack of public education by knowledgeable HCWs may have also contributed to popular belief in the negative propaganda [16]. Campaigns and health education in advance to the next anticipated influenza outbreaks could play an essential role in encouraging communities to accept vaccinations during similar future circumstances.

Side effects experienced by the vaccinated individuals in the cohort consisted of normal short-term adverse effects [17]. Therefore, the vaccine is promising for future use if any outbreak is expected, assuming that further assessment of the long-term adverse effects yields positive results.

Based on surveillance following the 1976 swine flu vaccination program, the risk of anaphylaxis from the influenza vaccination was estimated to be approximately one in every four million people. In 1976, Guillain-Barré syndrome was associated with receipt of the swine flu vaccine, with a risk of 1 per 100,000 individuals vaccinated [18]. Safety and efficacy are critical factors in determining the rate of vaccination in the general population. Governments that want to promote H1N1 vaccination will need to gain a better understanding of the barriers to and facilitators of acceptability before implementing full-scale vaccination programs [19].

The current study demonstrated a substantial increase in participant awareness. Most participants understood that applying as many protective measures as possible allows for the best protection from swine flu infection. Our results also suggest that frequent hand washing is seen as one of the most influential protective measure. When participants were asked about future vaccines three weeks after the vaccination campaign, an increased number of participants (11 out of 67) had changed their minds and would accept vaccination in the future. This change of opinion among the participants could contribute to a higher acceptance rate if vaccinations are offered during future pandemics. The presence of participants in the same campus for three weeks post-vaccination, coupled with an exchange of information between the accepting and refusing groups, may have been the reasons that some participants changed their willingness to receive a future vaccination. HCWs were seriously deficient in terms of their knowledge of influenza prevention. Extensive and sustained efforts to overcome these limitations are urgently needed among HCWs, regardless of whether they are involved in direct or indirect patient care [20]. These efforts will help to increase effective compliance among HCWs and the general public.

Several limitations of this study were considered and acknowledged by our research team. First, the inclusion of a specific cohort of National Guard employees limits the wider generalizability and application of the research findings, as these employees are mainly from the local area and have extensive experience with the Hajj. Therefore, our cohort may not feel threatened by participation in such an international mass gathering. Second, the small sample size of participants may have hindered the ability to detect statistical significance; this may have resulted in a type II error (i.e., the sample size was not sufficiently large to confirm a difference between the groups).

In the context of global panic surrounding H1N1 and the possibility of an outbreak in a large gathering such as the Hajj, this study found that the acceptance rate for mass vaccination was low among HCWs but acceptable among non-HCWs. Further, our study recognized and characterized major barriers preventing H1N1 vaccination acceptance. Another significant finding of our analysis was the report of mild (within the normal range) short-term adverse effects experienced by our cohort.