Influenza Vaccine — Safe, Effective, and Mistrusted

On August 10, 2010, the World Health Organization (WHO) declared an end to the 2009 influenza A (H1N1) pandemic. It is fortunate that the virus that had spread worldwide so quickly turned out to be less severe than was first feared. It is worth remembering, though, that an
earlier strain of H1N1 influenza — the one that emerged in 1918 — sparked the worst closely observed and recorded pandemic in history, killing an estimated 20 million to 40 million people worldwide.
The 2009 H1N1 virus did give us one gift of inestimable value: it provided a full-scale test of the ability of the United States to counter pandemic influenza. If we draw the right lessons from the response, we can considerably strengthen our country's public health preparedness.
The most obvious lesson is that we currently lack the capacity to develop, produce, and distribute a new vaccine in time to counter a fast-moving pandemic — a fact that reinforces the need for continued federal investments in the processes, policies, and infrastructure required to swiftly produce and distribute a pandemic vaccine. In addition to protecting vaccinees themselves against the effects of the virus, vaccination decreases the likelihood that an exposed person will pass virus on to others. If sufficient numbers of people can be vaccinated in time, an epidemic can be slowed or even stopped in its tracks.
Before March 2009, when the new H1N1 influenza burst onto the scene, the conventional wisdom held that the next pandemic strain would originate in Southeast Asia, and we would have weeks, if not months, to develop a pandemic vaccine. The conventional wisdom proved wrong. Despite an all-out effort that generated a safe and effective vaccine in record time, adequate stocks did not reach the public until December 2009. By that point, the pandemic had passed its peak, and public demand for vaccination was in swift decline. In the end, manufacturers were left with 70 million unused doses.1
The second lesson of the pandemic may be less obvious, but it is just as important as the first. Accelerating vaccine production is necessary but insufficient to counter a future pandemic. For no matter how quickly a safe and effective vaccine is produced, it will do little good if large numbers of people refuse to be vaccinated. In other words, any increase in supply must be matched by an equally substantial increase in demand — and the earlier during the course of an evolving pandemic, the better.
Increasing the public's acceptance of vaccination may be more difficult than addressing the technical and scientific challenges involved in quickly producing large quantities of a safe and effective vaccine. Consider that despite an unprecedented public education campaign and a worldwide pandemic, only about 20% of U.S. adults were vaccinated against pandemic influenza.2 Most striking of all, less than half of health care workers were vaccinated against it, despite the fact that they could inadvertently pass the infection on to medically vulnerable patients.3
There is little doubt that uptake of pandemic vaccine would have been greater had shipments reached the public earlier. However, quicker delivery might not have made as big a difference as some assume. Survey data collected by RAND and others indicate that even at the outset of the pandemic, when fear of H1N1 influenza was widespread, less than half of all adults were willing to get vaccinated against it.4 It is also likely that vaccination uptake would have been higher had the pandemic been more deadly than it turned out to be. Yet almost 20% of adults said they would not consider getting vaccinated, even if people in their community were sick or dying from pandemic influenza.5
It is tempting to lay blame for the lack of public enthusiasm at the feet of a small but highly vocal minority who are convinced that vaccines cause a variety of global ills, including autism. Although their effect on public confidence must be taken seriously, it should not distract attention from more comprehensive efforts to understand the full range of factors that motivate people to get vaccinated or discourage them from doing so.
Data from RAND's influenza vaccination tracking surveys suggest that a person's willingness to accept pandemic vaccination strongly depends on past experience with being vaccinated against seasonal influenza. Data collected during the early stages of the pandemic showed that the intention to be vaccinated against H1N1 was strongly associated with past uptake of seasonal vaccine.4 At later stages of the pandemic, regular users of seasonal influenza vaccine were nearly four times as likely as irregular users or nonusers of seasonal vaccine to be vaccinated against H1N1. Regular users of seasonal vaccine were significantly more likely to consider H1N1 a serious disease and were twice as likely as irregular users or nonusers to hold favorable attitudes about the safety and value of vaccinationThese data underscore the need to step up efforts to convince skeptics that influenza vaccination is a good idea — not only as an annual exercise in disease control but also as a way of strengthening public health preparedness. We hope that the new recommendations promulgated by the Advisory Committee on Immunization Practices (ACIP) will help. Rather than focus on “high-risk groups,” as has been done in the past, the ACIP now recommends annual influenza vaccination for everyone 6 months of age or older, except in cases of medical contraindications, such as a severe allergy to the vaccine. This change in position was inspired, in part, by two long-understood truths that were driven home by the pandemic: novel strains of influenza can cause severe illness in otherwise healthy, “low-risk” people, and vaccinating large numbers of healthy people protects others who are highly vulnerable to influenza and its complications.
Despite the importance of public acceptance, the science that would clarify the best ways of informing and motivating the public is severely underdeveloped. How can indifferent or negative attitudes toward vaccination be changed? A quick look at publicly funded research on the topic of influenza and influenza vaccination, made possible by the Research Portfolio Online Reporting Tool from the National Institutes of Health, indicates that over the past decade more than 95% of funding has been devoted to biomedical topics rather than to social and behavioral science. Clearly, cutting-edge laboratory science to enhance the safety and effectiveness of vaccines is vital to public health. But it is equally important to understand the forces that shape public views about the risks and benefits of vaccination. Without this knowledge, it will be impossible to translate biomedical advances into effective action.
Investments that enhance public acceptance of vaccination will yield substantial returns, in the form of reduced incidence and severity of disease as well as enhanced pandemic preparedness. A more balanced research portfolio is likely to be more successful than one that is heavily weighted toward biomedical research alone. We are fortunate that the pandemic that just passed was milder than expected. Next time, we may not be so lucky.
This article (10.1056/NEJMp1012333) was published on November 24, 2010, at NEJM.org.
The analysis and opinions presented here are those of the authors and do not necessarily represent those of RAND.
Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

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From RAND, Arlington, VA.

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