We examined the costs and benefits of vaccination in the autumn for the ongoing 2009 (H1N1) pandemic. Our analysis suggests that absent additional harms, earlier vaccination, as advised by the National Biodefense Science Board (60
), would save more costs and avert a greater number of deaths than vaccination later in the autumn. Because accelerating large-scale vaccination efforts in this time frame may be costly, we have provided a range of acceptable costs of vaccination, given different reproductive rates, to guide policymakers in situations in which they might consider speeding vaccine production and administration. We defined the number of individuals requiring vaccination to reduce widespread transmission in a metropolitan city under a broad range of possible reproductive rates and note that regardless of the timing of vaccination, complete population coverage is not necessary to reduce the viral reproductive rate sufficiently to help shorten the pandemic. These results have important ramifications both for vaccine production goals and preparations for a potentially unprecedented fall vaccination campaign.
We found that the effectiveness and cost-effectiveness of vaccination are most dependent on the speed at which the pandemic grows. Our finding that earlier vaccination saves more costs and averts more deaths may be most important for those areas in which there is more rapid growth of the pandemic; it is important to note that the virus is not spreading at the same rate throughout the United States, but appears to be evolving as different regional and local epidemics (11
). Several factors may delay the peak of the pandemic, leaving a greater proportion of the population susceptible to infection, and increasing the effectiveness and cost-effectiveness of vaccination later in the autumn. Viral characteristics that would delay the peak include a lower reproductive rate, a longer incubation period, and a shorter duration of infectiousness. Importantly, non-pharmaceutical interventions could also have a marked effect on the speed at which the pandemic grows: our analysis shows that increased implementation of highly effective non-pharmaceutical interventions, such as early use of hand hygiene and surgical masks (84
) can significantly delay the peak of the pandemic, increasing the effectiveness and cost-effectiveness of delayed vaccination. In contrast, if the epidemic grows rapidly and peaks in October, vaccination becomes substantially less effective and less cost-effective.
While greater than 50% population coverage with an effective vaccine for Pandemic (H1N1) may be desirable (94
), this goal does not appear to be logistically feasible for the autumn vaccination campaign. Our analysis suggests that vaccinating even 20% of the population can be effective and cost-effective. We also note that over a wide range of viral reproductive rates and pandemic growth scenarios, vaccinating up to 41% of the population can be sufficient to slow widespread viral transmission by inducing herd immunity within the population, shortening the pandemic.
We assumed that severe Pandemic (H1N1) vaccine side effects could occur in 1 in 100,000 vaccinated individuals (41
). Under these assumptions, vaccinating 20% of the city’s population in November would cause approximately 1 death secondary to severe vaccine side effects for every 437 lives saved from vaccination. We emphasize that our analysis assumes that vaccination would not cause additional harms, and we encourage thorough testing and evaluation of vaccines prior to large-scale vaccination campaigns (95
Key limitations of the analysis include an assumption that disease transmission occurs with homogenous mixing; all individuals, regardless of age and occupation, have the same frequency of contacts, and our model is not designed to make recommendations about the impacts of prioritizing vaccination for different groups. In the 1918 and 1957 pandemics, influenza was transmitted more readily in children in close proximity, such as schools (96
). If this pattern occurs in the 2009 (H1N1) Pandemic, heterogeneous mixing would result in a more rapid initial spread of the pandemic, followed by slowing as it spreads to lower contact rates (97
). Our analysis provides insights into the magnitude of the pandemic and the response to vaccination (98
); however, policymakers may wish to prioritize vaccination based on differing patterns of transmission in specific age groups, as well as groups noted to have higher morbidity and mortality from Pandemic (H1N1) infection.
We did not account for all costs to uninfected individuals in the setting of the 2009 (H1N1) pandemic; costs incurred by uninfected individuals from school and workplace closures, decreases in tourism and group recreation, and loss of firm-specific knowledge may be greater than costs to sick individuals (99
). We did not include potential savings of effective vaccination, such as limiting displacement of hospitalized patients, or decreasing school and workplace closures. However, including these costs and savings would make vaccination even more cost-effective or cost-saving. Additionally, we account for normal health care expenditures, which significantly increase total costs for each life saved through vaccination; not including costs of long-term normal health care in our analysis would also make Pandemic (H1N1) vaccination more cost-saving.
Covering the majority of the population with an effective vaccine for Pandemic (H1N1) would prevent the most morbidity and mortality from influenza, but will not be achievable within the short time frame for vaccine development and with projected supplies (88
). Our analysis suggests that vaccination can be a valuable and effective intervention even it is reaches less than half the population. Many uncertainties remain about the transmissibility and mortality of Pandemic (H1N1) 2009; however, absent serious vaccine side effects, vaccination earlier in the autumn is likely to be cost-saving and avert a greater number of deaths than later vaccination, which highlights the urgency of vaccine development, with attention to safety. On 24 June, 2009, President Obama signed into law an emergency spending bill devoting $2 billion in additional funding to 2009 (H1N1) Pandemic mitigation efforts (100
); our analyses suggest that vaccination strategies could be a valuable component of such efforts.