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The Allocation of Vaccines during an Influenza Pandemic In spring 2009, the emergence of a novel strain of the H1N1 influenza virus in humans led to a global pandemic. Initially (and imprecisely) referred to as "swine flu" by some, what began as an outbreak in Mexico and the Southwestern United States rapidly grew to a worldwide threat to public health. Soon after the initial identification of the virus, governments around the world committed significant resources to H1N1 influenza, developing plans for treatment and prevention amid great uncertainty regarding both the scope and severity of the threat. Central to these plans was a debate regarding the allocation of vaccines once available, particularly in the early stages of the pandemic when supply would be extremely limited. These discussions in part adapted vaccine allocation models established for a potential H5N1 ('bird flu') pandemic, a long-standing focus of public health preparedness efforts. Vaccines as Part of the U.S. Response to the H1N1 Pandemic The development of an H1N1 vaccine began immediately after the identification of the virus. Because of well-known limitations in the current influenza vaccine manufacturing process, the U.S. government anticipated that initial vaccine supplies would be inadequate to address demand. Thus, in July 2009, the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) issued recommendations for the prioritization of vaccine distribution. The ACIP identified five target groups thought to be at greater than average risk for infection or complications to whom vaccine doses should be administered first: pregnant women, people who live with or have regular contact with infants under 6 months of age (who are too young to receive the vaccine themselves), health-care and emergency medical services personnel, children and young adults between the ages of 6 months and 24 years, and those with existing health conditions that put them at increased risk of complications.1 The approximately 159 million people classified within these groups were to be given priority in receiving the vaccine once it became available. The ACIP also identified a subset of this group--approximately 42 million people--who were to be the first recipients in an extreme shortage: pregnant women, household contacts of infants under 6 months of age, health-care and emergency medical services personnel who have contact with patients or infectious material, children between the ages of 6 months and 4 years, and children between the ages of 5 and 18 years with health conditions contributing to the risk of complications.2 After all target groups were offered the opportunity for vaccination, vaccine doses would then be made available to the full U.S. population as supplies permitted. Because supply and demand were expected to vary regionally, state and local officials and vaccine providers were responsible for developing distribution strategies reflecting local circumstances and available health-care infrastructure The first doses of H1N1 influenza vaccine was released in mid-October 2009, six months after the first cluster of infections was identified and only a few days before President Obama declared the virus a national emergency. The initial quantity of vaccine was far less than had been predicted by health officials weeks earlier, with only about 16.5 million doses initially available.3 Public frustration mounted in the face of the shortage. This difficulty in obtaining the vaccine may have contributed to the ultimately low rates of national coverage, according to observers. "Fears about the pandemic fostered wide-scale anxiety and spawned long lines as the first doses trickled in amid the second wave of infections [in the fall of 2009]. By the time the vaccine was plentiful, demand had dissipated," wrote a reporter for the Washington Post.4 By the end of January 2010, after vaccine supply has dramatically improved, the median coverage by state was only 33.2% for members of the initial target groups. Overall, the median coverage for the full population was 23.9%, with significant disparities between states.5 By the conclusion of the mass vaccination campaign in spring 2010, between 81 and 91 million of the 229 million H1N1 vaccine doses purchased by the government were administered. While a portion of this surplus was donated to other countries or reserved for future use, the majority of this excess supply was to be discarded.6 Previous Models for Vaccine Allocation The H1N1 pandemic confirmed previous estimates that it would take at least six months to produce an effective vaccine in the event of an influenza pandemic. Even after the initial identification of the precise pandemic strain, known production limitations delayed the manufacture the vaccine.7 When such scarcity is unavoidable, the establishment of regulations for the just and economical distribution of vaccines is absolutely imperative, National Institutes of Health (NIH) researchers Ezekiel Emanuel and Alan Wertheimer noted in 2006, long before the arrival of H1N1 influenza.8 They cautioned that, regardless of its nature, "any principle of rationing will offend many." While some are indeed likely to be offended by such discussions, a variety of models were developed in recent years in preparation for a possible influenza pandemic and a limited supply of vaccine. In 2006, a time of considerable anxiety regarding a potential avian flu pandemic, the ACIP and the National Vaccine Advisory Committee (NVAC) released recommendations for vaccine allocation in the event of a global influenza pandemic. They recommended prioritizing the elderly, patients with two or more high-risk conditions, and those with a history of severe pneumonia for limited vaccine doses. First responders, key leaders in government, healthy senior citizens, and those with one risk factor would receive the vaccine next, followed by employees of the utility, transportation, and telecommunications industries. Jon Abramson, the then-chair of one of the two federal advisory panels collaborating on these recommendations, explained that equity was the primary principle used in the formulation of these guidelines, and that members of the panels "strongly felt [that] you cannot prioritize on the basis of age or gender or race."9 The ACIP altered this view in response to H1N1 because the virus was observed to disproportionately affect the young, while those over 65 seemed to possess a degree of immunity.10 The 2006 NVAC/ACIP recommendations were immediately met with criticism. Ceci Connolly of the Washington Post noted, "Already federal agencies are sparring over who is 'critical,' posing no-win dilemmas such as: air traffic controllers or border patrol officers?"11 Emanuel and Wertheimer described the NVAC/ACIP plan as "inadequate on both ethical and practical accounts" and suggested an alternative plan known as "IRPOP," investment refinement combined with the public-order principle.12,13 Both the NVAC/ACIP and IRPOP models recommended that vaccines should be first distributed to front-line medical staff, first responders, and military personnel.14 Under the principle of investment refinement, the IRPOP next gives priority to 13- to 40-year-olds. The investment refinement principle determines allocation based on age group, awarding priority "on the basis of the amount the person invested in his or her life balanced by the amount left to live. Within this framework, 20-year-olds are valued more than 1-year-olds because the older individuals have more developed interests, hopes, and plans but have not had an opportunity to realize them."15 A key principle guiding Emanuel and Wertheimer's model is saving the most "life-years" rather than the most lives. "A 65-year-old has had great investment that is largely fulfilled....there is a good ethical argument that even if vaccinating the elderly saved the most life years, one should prefer the young over the old because the young have more unfulfilled life."16 Vaccinating those who are predicted to have the highest risk of hospitalization or death has been criticized as a poor system of prioritization in a pandemic.17 Advocates of the IRPOP model contend that systems of allocation should take into consideration factors such as risk severity, risk likelihood, transmissibility, and vaccine effectiveness.18 Furthermore, the elderly may reap less benefit from influenza vaccines because of a diminished immune response. They are also less likely to transmit the disease because they tend to spend less time in high-density areas such as schools and offices.19 Similarly, though very young children do not receive high priority within IRPOP, they can be protected through the implementation of school closures and through other social isolation measures other than vaccination. Critics of the IRPOP model point to the exclusion of children under age 13 in the top priority grouping. They also cite the model's failure to take into account the possibility of age-related differential mortality rates and its potential to perpetuate existing social injustices. (The 2009-10 H1N1 influenza pandemic validated the first of these concerns.) The targeted vaccination of children--whom researchers describe as the group "most responsible for initiating and perpetuating epidemics"--may effectively limit the overall spread of infection. Epidemiological and modeling studies indicate that campaigns focusing on children dramatically reduce community-wide disease transmission.20 Determining Policy In the United States, policy recommendation regarding the allocation of vaccines are largely set by the Advisory Committee on Immunization Practices, a federal entity that develops written recommendations for the safe and effective use of vaccines for the CDC and for officials within the U.S. Department of Health and Human Services.21 The global body that produces vaccine recommendations is the Strategic Advisory Group of Experts (SAGE) on Immunization, an advisory group of the World Health Organization (WHO). Among other duties, SAGE is responsible for devising global strategies for the delivery and prioritization of vaccines.22 During the global H1N1 pandemic, WHO emphasized both the humanitarian and practical necessity of providing the vaccine to developing nations, urging wealthy governments and pharmaceutical companies to donate or subsidize vaccine doses. Conclusion As the various prioritization models would suggest, there is no single, simple solution for allocating vaccine in a pandemic. Advance planning is further complicated by difficulties predicting the likelihood and severity of risk. During the 1918 influenza pandemic, which is often employed as a model for contemporary planning, mortality rates were highest among 20 to 40-year-olds and children under the age of five. In the pandemics of 1957 and 1968, however, the very young and the very old were most susceptible.23 Despite at-times dire pandemic forecasts and less-than-desired vaccination rates, the CDC estimates that the 2009-10 H1N1 pandemic resulted in 12,000 fatalities. By comparison, seasonal flu is thought to cause three times as many deaths each year.24 However, CDC officials observed that H1N1 tended to most severely affect pregnant women, children, and otherwise healthy young adults, creating a more significant health impact than numbers alone might suggest.25 Also concerning was the variation in vaccination rates among states, which, according to CDC, "suggests opportunities for improvement in future seasons, such as maintaining and increasing the reach of networks of private providers as vaccinators and distributing more vaccine through public venues (e.g., schools)."26 Overall, the discouraging H1N1 vaccination rates for priority groups and the general public indicate considerable opportunity for improvement in building support for future mass vaccination campaigns. While advances in vaccine production may improve the speed and quantity of available vaccine doses in future pandemics, some limits on production are unavoidable. In order for any allocation model to be effective, it must be thoughtfully considered and convincingly presented to all stakeholders. Critically important to these efforts is the public, whose support is essential to the success of any vaccination program. -- By Laura Backup, Swarthmore University (lbackup1@swarthmore.edu) and Jessica Ho, University of Pennsylvania (yjho@sas.upenn.edu); Updated July 2010.
1 CDC. "Use of Influenza A (H1N1) 2009 Monovalent Vaccine Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009." MMWR 58, RR10 (2009);1-8 |
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