In 1971, the U.S. Centers for Disease Control and Prevention (CDC) recommended discontinuation of routine immunization and vaccination requirements for smallpoxﾠin the U.S.

Because of vaccination programs and quarantine regulations, the risk of importation of smallpox into the U.S. was reduced by the 1960s. In 1976, the recommendation for routine vaccination of health-care workers was also discontinued.

In 1980, the Immunization Practices Advisory Committee (ACIP) recommended the use of vaccinia vaccine to protect laboratory workers from possible infection while working with nonvariola orthopoxviruses (e.g., vaccinia and monkeypox)(6).

In 1984, these recommendations were included in guidelines for biosafety in microbiological and biomedical laboratories. These guidelines expanded the recommendation to include persons working in animal-care areas where studies with orthopoxviruses were being conducted and recommended that these workers have documented evidence of satisfactory smallpox vaccination within the preceding 3 years.

The CDC has provided vaccinia vaccine for these laboratory workers since 1983.