Dr. James R. Shannon, former director of the National institute of health declared, "the only safe vaccine is one that is never used."

Cowpox vaccine was believed able to immunize people against smallpox. At the time this vaccine was introduced, there was already a decline in the number of cases of smallpox.

Japan introduced compulsory vaccination in 1872. In 1892 there were 165,774 cases of smallpox with 29,979 deaths despite the vaccination program. A stringent compulsory smallpox vaccine program, which prosecuted those refusing the vaccine, was instituted in England in 1867.

Within 4 years 97.5 % of persons between 2 and 50 had been vaccinated. The following year England experienced the worst smallpox epidemic[1] in its history with 44,840 deaths. Between 1871 and 1880 the incidence of smallpox escalated from 28 to 46 per 100,000. The smallpox vaccine does not work.

Much of the success attributed to vaccination programs may actually have been due to improvement in public health related to water quality and sanitation, less crowded living conditions, better nutrition, and higher standards of living.