Preparedness for a smallpox outbreak: comparing metrics for assessing levels of vaccination among health-care workers by state

By mid-2005, less than 17% of smallpox vaccine doses distributed to American states for health-care workers (HCWs) during the CDC campaign had been used. To understand how states responded, vaccination patterns were studied. Metrics were calculated to compare the level of preparedness for a smallpox outbreak in terms of absolute numbers of HCWs vaccinated compared to the percentage of doses distributed to each state, the rate of vaccination per capita population, and the percentage of HCWs vaccinated compared to the number the CDC recommended. States were then ranked. Results showed that rankings for all four metrics were statistically different (P<0.0001). In addition, when ranks were assigned to quartiles, the states directly affected on 9/11/01 ranked lowest and states widely perceived to be at lower terror risk ranked in the top. These results underscore the need to critically examine how to define an appropriate level of preparedness for a smallpox outbreak.