Vaccine shortages during epidemics or pandemics involving novel pathogens, such as H1N1 (swine influenza) in 2009, may be the rule rather than the exception. There is usually little time to develop, test, approve, and manufacture a vaccine. Despite swift decision making by public health officials in spring 2009, the first H1N1 vaccines were not available until October, close to the pandemic’s peak. This timing represented an improvement over past influenza pandemics, like those of 19571
But unless technological advances can speed up the development of new vaccines, shortages are likely to recur.
When vaccines are in short supply, distributing them quickly and equitably among populations and localities can be a difficult challenge. During the H1N1 pandemic, the Department of Health and Human Services allocated available vaccines to each state and territory by population size and shipped vaccines directly to locations designated by each jurisdiction.3
By October 14, 2009, of 11,422,900 allocated 2009 H1N1 influenza vaccine doses, only 5,885,900 doses had been shipped. California had received 836,900 doses, the highest of any jurisdiction, while American Samoa and the Marshall Islands had not received any doses. Each jurisdiction, in turn, decided which of its residents would get vaccines first. However, even with the best intentions, inadequate infrastructure, geographical or socioeconomic barriers, or cultural differences can lead to inequitable access to vaccines.
The distribution of vaccination locations and personnel might not be equal across counties.4
Although official planners may seek to allocate vaccines by risk status, economic and operational challenges—such as unequal access to health care facilities or resources—may prevent this careful distribution. For instance, during the 2009 H1N1 pandemic, Los Angeles reported unequal vaccine distribution, with relatively less vaccine available in areas with higher percentages of uninsured and low-income residents. South Los Angeles County received one dose per five people, while West Los Angeles County, which includes Malibu, Santa Monica, and Beverly Hills, received one dose per two people.5
Moreover, geographic proximity to vaccination locations does not necessarily guarantee access to vaccines. Some people may be unable to receive a vaccination because they lack insurance; because their insurance restricts where they can get preventive care; or because they cannot afford to miss work to be vaccinated. Still others may lack sufficient health literacy to realize that they should get a vaccine.4,6,7
Moreover, many poor people cross county lines to go to work and school, making it harder for them to get to vaccination centers in their own county.7,8
If vaccines are allocated based on the number of county residents, nonresidents might not be able to receive vaccines.
Studies have shown that poorer people may have less access to medical care, including vaccination, than wealthier people.4,9–13
Even in a population with equal access to overall care, there may be racial disparities in who receives antiviral treatment.14
A national survey found racial and ethnic disparities in H1N1 exposure risk (including differences in dependence on public transportation and in the ability to work at home if necessary), susceptibility to severe diseases (including higher rates of self-reported chronic conditions and immunosupression), and health care access.15
Naturally, justice argues for equitable distribution among poor and rich residents alike. But in addition, could equity help reduce an epidemic’s severity—for example, by ensuring that wealthy counties do not receive more than their fair share of vaccines?16
Many low-income neighborhoods have fairly high population densities, which means that many people interact closely with each other and that contagious diseases can spread quickly.7,8,17
Important questions remain: What are the potential effects of unequal access to vaccines among poor counties? Does society have an interest in ensuring that the vaccine distribution strategy treats these populations equitably?
We explored the effects of differential vaccination by socioeconomic status using a detailed computer simulation model of the Washington, D.C., metropolitan region. Our team developed the model during work with the Office of the Assistant Secretary for Preparedness and Response at the Department of Health and Human Services during the 2009 H1N1 pandemic. We examined how the course of the pandemic might have been affected by vaccinating residents of counties with the highest and lowest median household incomes at different rates and times.