Following initial heightened fears, the public’s attitude towards the H1N1 virus has changed, with many people now skeptical over the potential health threat. However, the virus is expected to continue to spread and stabilizing supply, along with educating the public about the medical and societal need for vaccination will be crucial for the success of H1N1 infection control.
The current influenza A (H1N1) pandemic has been spreading around the world since its first outbreak in March 2009, infecting an increasing number of people. According to the World Health Organization (WHO), as of October 25, 2009, there have been more than 440,000 laboratory confirmed cases of influenza A (H1N1) and over 5,700 deaths worldwide. As a consequence of initial fears comparing the H1N1 pandemic to the 1918 pandemic, which caused up to 100 million deaths across the world, international organizations and governments around the world were fast to order stockpiles of influenza antivirals and pandemic influenza vaccines in order to protect their citizens. By the end of August 2009, most Western countries had established plans for organized vaccination campaigns for influenza A (H1N1).
Key target groups prioritized for vaccination include pregnant women, people who live with or care for children younger than six months of age, healthcare and emergency medical services personnel, persons between the ages of six months and 24 years, and people aged 25 through 64 years of age with chronic health conditions or compromised immune systems. Many countries went as far as ordering vaccines to supply the whole population.
While public opinion towards H1N1 vaccination was very positive at the beginning of the pandemic, driven by the great perceived risk of infection, there has been a significant change since. According to a survey conducted by the Harvard School of Public Health in early October 2009, just 40% of US adults were “absolutely certain” they would get the H1N1 vaccine for themselves, with a further 40% stating they would not get it. A survey performed for news magazine “Der Spiegel” in Germany in late October found that only 17% of respondents would get vaccinated, while 27% said they would not get the vaccine. This change in attitude has several explanations, including believing that vaccination is unnecessary, delays in vaccine supply, as well as distrust of available vaccines.
H1N1 is currently underestimated in the general population
During the initial outbreak of H1N1 in Mexico, the virus seemed to be associated with high morbidity and mortality, sparking widespread calls for a rapid development and supply of vaccines. However, as the virus spread further, it became clear that infections mostly took a mild course and only rarely resulted in hospitalization or death. In September 2009, new estimates suggested that the H1N1 death rate is less than 0.1% and compares to a moderate year of seasonal influenza. The mostly mild character of the infection has led to a change of attitude in the general public, with many people now deeming vaccination unnecessary, particularly as the number of new infections remained limited over the summer months in the northern hemisphere.
However, this perception is risky. Experts have long warned of a second wave of infections in autumn and winter, and first signs of this are now emerging. In the US, the number of confirmed H1N1 cases per week more than tripled between late August and October, reaching almost 5,500 cases in the week ending October 18. In Germany, the number of diagnosed cases increased from 1,860 in the week ending October 18 to 3,075 in the following week.
Considering that most cases are not officially diagnosed and therefore do not appear in the statistics, the real number of cases can be estimated much higher: The UK Health Protection Agency’s (HPA) models estimate a number of 78,000 new cases in England in the week ending October 29, representing a 56% increase on the previous week. The accelerating pandemic is bound to result in a growing number of hospitalizations and deaths. According to a study led by researchers from the California Department of Public Health, in 1,088 hospitalized swine flu patients, the mortality rate for H1N1 in hospitalized patients reached 11%, with fatalities most common in the elderly (18-20%) and children younger than 18 (7%). This clearly shows that despite the low infection rates over the summer, H1N1 is set to spread further, proving a very valid case for widespread vaccination.
Manufacturing delays limit vaccination rates
Supply problems represent an important reason for the currently low vaccination uptake. Keen to maximize their sales and somewhat optimistically relying on a smooth manufacturing process, some H1N1 vaccine manufacturers promised delivery of their first vaccine batches as early as August 2009, which turned out to be unrealistic. In the US, for example, only 26.6 million vaccine doses, from a total of 250 million ordered, had been made available by October 30. Countries that relied on the vaccine makers’ promises advertised the start of their vaccination campaigns for early October, but then had to delay and disrupt their immunization campaigns, thereby losing momentum for vaccination efforts in the general public.
European backlash against adjuvanted H1N1 vaccines
The composition of some H1N1 vaccines is a further factor affecting their uptake, particularly in Europe. H1N1 vaccines differ significantly between the US and the EU. The FDA has approved four pandemic vaccines: injected formulations manufactured by Sanofi Pasteur, Novartis and CSL, as well as a nasal spray vaccine manufactured by MedImmune (part of AstraZeneca). None of these vaccines contains an adjuvant, and all four products are manufactured in eggs, using identical procedures as for conventional seasonal influenza vaccines.
In contrast, bound by the previously granted approval for mock-up pandemic vaccines in preparation for the clinically more severe influenza H5N1, European regulators have opted for a different strategy. All three European H1N1 vaccines rely on new vaccine technologies: GSK’s Pandemrix and Novartis’ Focetria contain novel vaccine adjuvants, whereas Baxter’s Celvapan is manufactured in cell cultures, not chicken eggs. Adjuvanted vaccines create an improved immune response, thereby enabling the use of lower antigen doses, which maximizes the number of doses which can be manufactured. However, they are also associated with increased reactogenicity, i.e. causing more injection site reactions as well as dizziness, fatigue or fever compared to non-adjuvanted vaccines. While adjuvanted vaccines would be of great use during a clinically severe pandemic caused by a more virulent virus like H5N1, the need for adjuvants in a milder pandemic such as the current one is less obvious.
The issue attracted particular controversy in Germany when it emerged that due to the structure of the supply contracts, the general population was to receive GSK’s adjuvanted vaccine Pandemrix, while government officials and the army would be using Baxter’s non-adjuvanted Celvapan. In addition, none of the three vaccines approved in Europe have been tested in pregnant women, who are one of the key priority groups for vaccination. As a consequence, an increasing number of people perceive H1N1 vaccination as a commercial ploy by the pharmaceutical industry rather than a medical necessity and refuse to get vaccinated.
Looking forward: awareness is the key issue
Despite the usually mild course of H1N1 infections and the limited number of transmissions over the summer months, the current pandemic is far from over. Recent epidemiological data show a rapid increase of infections in October, and studies have shown a disproportionally high morbidity and mortality of H1N1 infections in several groups including pregnant women, chronically ill or small children.
In order to avoid the potentially severe medical and economic consequences arising from further spread of the virus, a rapid uptake of the vaccination is crucially important at this time. The largely negative public attitude towards H1N1 immunization poses a major risk to infection control. For both manufacturers and campaign organizers alike, it is now vital to make every effort to produce and distribute H1N1 vaccines as fast as possible in order to be able to vaccinate people before widespread transmission renders vaccination obsolete.
In addition, Datamonitor believes that re-igniting and sustaining public awareness of the potential dangers of H1N1 is crucial for the success of H1N1 infection control. Particular emphasis should be placed on making people understand that by choosing not to get vaccinated, they do not only risk falling ill themselves, but may endanger those in their environment who are at greater risk of severe disease and death through H1N1, e.g. small children, elderly or pregnant women.
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