In April 2009, the Mexican Secretariat of Health reported an outbreak of respiratory disease. In the affected patients, a novel swine origin influenza A (H1N1 09) virus was detected [1, 2]. Evidence that this new strain could pass from human-to-human led the World Health Organization (WHO) to quickly raise its pandemic alert level to phase 5 on April 29^th, representing "a strong signal that a pandemic is imminent and that the time to finalise the organisation, communication and implementation of the planned mitigation measures is short" [3]. After documentation of human-to-human transmission of the virus in at least three countries across two WHO regions, the WHO raised the pandemic level to 6 on June 11^th [4].

Australia experienced the pandemic influenza A (H1N1) 2009 outbreak at the same time that seasonal influenza circulation was expected. Victoria was the first Australian state to report a significant number of cases, followed by New South Wales [5]. The first wave lasted 18 weeks in Australia from mid-May to late September 2009. The rate of hospitalisations was 23 per 100,000 population, with indigenous Australians overrepresented [6]. The highest rate of hospitalisation occurred among children under 5 years of age [6]. As of February 19^th 2010, there have been 37,713 confirmed cases of pandemic (H1N1) 2009 in Australia, including 191 pandemic influenza-associated deaths [7].

Since 17 June 2009, Australia's response to the pandemic has been guided by the PROTECT phase within the Australian Health Management Plan for Pandemic Influenza (AHMPPI) [8]. This newly developed phase focused on identifying and treating infection in people with moderate to severe disease and those with certain risk factors (i.e. underlying chronic diseases), controlling outbreaks in institutions and monitoring hospitalisations [9]. On September 30th 2009, the pandemic (H1N1) 2009 vaccine was made available to adults and children aged 10 years and over, in Australia. The Australian Government purchased 21 million doses of H1N1 vaccine [10]. On the basis of local safety and immunogenicity trial results the pandemic H1N1 09 influenza vaccine was registered by the Australian Therapeutic Goods Administration [11].

To assess the associations between risk perceptions of the pandemic (H1N1) 2009 influenza and intended protective behaviour changes, including willingness to be vaccinated, we carried out a community survey in Sydney, Australia. The aim of this study was to examine attitudes, concerns and behaviours around pandemic influenza (H1N1) 2009 in the general public.

Between September 5^th and October 3^rd 2009, we conducted a cross-sectional intercept survey in Sydney Australia to explore the community beliefs and risk perceptions to the influenza A (H1N1) 2009 pandemic and their attitude towards the vaccine.

Responses were received from 491/627 participants regarding why they would or would not accept the pandemic H1N1 2009 influenza vaccine. Close to half (49.9%, 245/491) of the responses were classified as being in support of the novel H1N1 vaccine. A common supportive reason was the belief that the vaccine would provide self protection (32.6%, 80/245), followed by the belief that the novel vaccine would provide general protection to the community and would halt the spread of the disease (31%, 76/245). Some participants classified themselves at high risk of influenza and therefore believed it was extremely important to be vaccinated, whereas others expressed an obligation to be vaccinated because of work commitments. A general belief or confidence in vaccination was commonly expressed as a reason for accepting the vaccine. Some participants believed that the novel H1N1 2009 influenza vaccine was the same as the "normal influenza vaccine" and therefore intended to be vaccinated as they would normally do against seasonal influenza.

The main reasons given for not accepting the new vaccine included the belief that the pandemic H1N1 2009 influenza situation was not serious enough to warrant vaccination (29.3%, 72/246,) or they did not perceive themselves to be at-risk (17.1%, 42/246) (Figure 1). Many people believed that H1N1 was just "another" influenza strain or it was just the "normal" flu. For some participants who expressed concerns, the focus related to the clinical trials conducted or the safety of the vaccine and the side-effects. Comments included a belief that vaccination for the novel H1N1 influenza strain was unnecessary because they were young and/or healthy and they believed that their immune system could deal with the virus. One male participant aged 55-64 years stated "I see no reason to treat swine flu any more seriously than flu. Maintaining a healthy lifestyle is much more important".

On the 18th of September 2009, Australia's independent medicines' regulator, the Therapeutic Goods Administration (TGA), announced it was to register the CSL Biotherapies pandemic (H1N1) 2009 influenza vaccine. Human adult trials had indicated that the pandemic vaccine was similar to that of the seasonal influenza vaccine with a high safety and low adverse events profile [11, 15]. The registration announcement marked the commencement of the vaccination program for Australian adults. However, it also came at a time when many countries in the temperate regions of the southern hemisphere (Chile, Argentina, Australia, and New Zealand) had passed the peak of their winter influenza epidemic.

We found that less than 20% of our sample perceived that they were at significantly high risk of acquiring H1N1. This finding is comparable to the results reported in our earlier survey, which was conducted in Sydney during the WHO Pandemic Phase Five [12]. Our results are also echoed in other H1N1 studies conducted in Australia and overseas. For example, Lau et al found that only 10% of their participants (Hong Kong general public) considered themselves (10%, n = 31), their family members (10%, n = 30), or the general public (12%, n = 35) to have a high or very high chance of contracting A/H1N1 in the next year [16]. Eastwood et al, reported a slightly higher proportion (25%) of their cohort (Australian residents) perceived themselves to be at increased risk of infection [17]. It is perhaps not surprising that there is a low perception of risk amongst the community, as many of the reports on H1N1 in the newspapers and other media channels documented the virus as only causing mild influenza.

The acceptance of, and adherence to public health measures by the population depends largely on the way people perceive a threat. Pre-pandemic surveys and post-SARS studies have illustrated a dose-response relationship between the severity of pandemic and public response [18, 19]. Given the reported mildness of the H1N1 2009 pandemic and overall low anxiety expressed by our surveyed participant's, low rates of behaviour change could have been expected. Surprisingly however, over half of our participants changed at least one, and commonly two, behaviours in response to the situation. This is in stark contrast with the findings of Rubin et al [13], who reported that in the early stages of the pandemic, only forty nine people (4.9%) engaged in one or more of the avoidance behaviours, and 377 (37.8%) said that they had carried out one or more of the three recommended behaviours. Whilst our participants did not believe that they were at high risk of acquiring the disease, the concerns about the consequences if caught may have been sufficient enabler to adopt relatively simple changes in behaviour.

Given that pandemic H1N1 2009 influenza was generally mild in those without risk factors, the Australian Government revised its pandemic plan to include the PROTECT phase, focusing on managing local outbreaks especially in vulnerable groups in whom disease may be serious [20]. As part of this revised plan certain measures employed at earlier stages of the national response were adjusted to ensure they supported the current situation. Although this phase continued to promote individual protection measures, such as personal hygiene, cough etiquette and voluntary isolation if symptomatic, it did not recommend the general avoidance of public places or activities. It was not surprising that few of our participants reported to keep away from public places and public transportation.

People most vulnerable to pandemic H1N1 2009 influenza infection, such as those with chronic respiratory disease, diabetes, cancer, severe obesity and conditions that suppress the immune system, as well as pregnant women and Indigenous Australians were encouraged to be the first recipients of the H1N1 vaccine. However, the vaccine was also made freely available to all Australians, through their local primary health care provider or immunisation provider. In comparison, in Australian the annual influenza vaccine is only provided free to Indigenous people aged over 50, or aged 15 to 49 who are at high risk (according to NHMRC recommendations), and all adults aged 65 years and older under the National Immunisation Program [21]. National provisional data collected in November and December 2009 by the Australian Institute of Health and Welfare showed that among the adult age groups (ages 18 to 64 years), there had only been a 14% uptake of the pandemic H1N1 2009 influenza vaccine [22]. In comparison, receipt of the vaccine was three times higher in those aged 65 years and over (42%) [22].

Given that many of our participants believed that the pandemic situation was over, it was pleasing to find that 54% of those surveyed in our study indicated a willingness to receive pandemic H1N1 2009 influenza vaccine. International studies assessing willingness to receive the pandemic H1N1 2009 influenza vaccine have reported rates that range from 36.9% (Greece [23]) to 49.6% (United States [24]). Our findings also suggest that beliefs about seasonal influenza vaccination will influence uptake of novel H1N1 vaccine. For example, we determined that (1) annual influenza recipients were significantly more likely to accept the pandemic H1N1 2009 influenza vaccine compared to their unvaccinated counterparts and (2) many participants likened the H1N1 influenza strain to being a "normal" strain of influenza, which was no more "serious" or "dangerous".

While 45% of our participants believed that the H1N1 vaccine would protect them against acquiring "swine flu", a similar proportion were concerned about the safety of the vaccine and the possibility of side effects. Common fears expressed, were that: (1) the vaccine had been "rushed through"; (2) there had been "insufficient research"; (3) the vaccine had not been "tested adequately" and (4) "long term studies" were required to ensure its "safety". This suggests that many of our participants have a lack of understanding about the process of developing seasonal influenza vaccine based on the probability of strains. While we only looked at a small subset of the population in Sydney, if these results were found to be representative, educational materials distributed about the pandemic influenza vaccine should focus on its safety record, manufacturing and the similarities between seasonal influenza vaccination and pandemic vaccine to help dispel these fears. Vaccine uptake may also be increased if General Practitioners actively promote the pandemic vaccine to their patients, given the fact that we found higher rates of compliance for physician recommended vaccination, than for government recommendation.

This study has several limitations. Firstly, we only recruited from one city of Australia. We therefore recognise the limitations of applying the results of this study to the broader Australian population. Secondly, people who could not communicate in English were excluded from the sample, which may have affected representation of ethnic minorities. Additional research is required to examine the differing reactions to the outbreak among these groups. Thirdly, as participation in our study was on a voluntary basis, this study has potential for self-selection bias by community members who are particularly concerned about pandemic influenza. Fourthly, this survey measured the samples views at a specific point in time, therefore the beliefs and attitudes reflect the information available at that time. We also did not elaborate on "requests by authorities," possibly causing participants to confuse mandatory behaviours with behaviours strongly recommended by public health authorities.

While, most participants did not believe they were at high risk of acquiring pandemic H1N1 2009 influenza, over half of the sample indicated that they would accept the vaccine. Participants who were vaccinated against the seasonal influenza were more likely to intend to receive the pandemic H1N1 2009 influenza vaccine. Concerns about safety, the possibility of side effects and the vaccine development process need to be addressed.