Mass smallpox vaccination and cardiac deaths, New York City, 1947.

In April 1947, during a smallpox outbreak in New York City (NYC), more than 6 million people were vaccinated. To determine whether vaccination increased cardiac death, we reviewed NYC death certificates for comparable periods in 1946, 1947, and 1948 (N = 81,529) and calculated adjusted relative death rates for the postvaccination period. No increases in cardiac deaths were observed.