PHILADELPHIA, Penn. — The surprise discovery of several frozen vials labeled "smallpox" at a Pennsylvania lab this week did not turn out to be a hidden source of the eradicated virus, the CDC announced Thursday.
The vials were found at a Pennsylvania facility that conducts vaccine research, the Associated Press reported. The Centers for Disease Control and Prevention said Wednesday the vials “were incidentally discovered by a laboratory worker” who was cleaning out the freezer. An official said the vials' contents appeared intact and there was no indication anyone was exposed to the contents.
The World Health Organization has designated only two sites for smallpox storage. One is at the CDC in Atlanta and another is in Russia.
According to the CDC's follow-up statement on Thursday, laboratory testing of the vials found that they contained vaccinia, the virus used in the smallpox vaccine. There was no evidence that the vials contained any of the variola virus, which causes smallpox.
"CDC is in close contact with state and local health officials, law enforcement, and the World Health Organization about these findings," the agency said.
The freezer facility in Pennsylvania was secured after the discovery on Monday, and the CDC said that the staff followed standard protocols for notifying the federal government of a potential discovery. The vials were immediately sent for testing.
Due to the success of smallpox vaccines, the last natural outbreak of the disease in the US happened in 1949. In 1980, the World Health Assembly declared smallpox to have been eradicated, with no naturally occurring cases detected since.
The Associated Press contributed to this report.