CDC: 14 lab workers had orthopoxvirus infections in past decade
At least 14 US laboratory workers contracted vaccinia or cowpox virus infections from on-the-job exposures in the past decade, a Centers for Disease Control and Prevention (CDC) official reported at a federal advisory committee meeting yesterday.
Speaking to the Advisory Committee on Immunization Practices (ACIP), Brett Petersen, MD, said 26 lab-worker exposures to orthopoxviruses have been reported to the CDC since 2004, and 14 (54%) of those resulted in infections. Four of the workers had to be hospitalized, he said.
Twelve (86%) of the 14 infections involved vacinnia virus and 2 (14%) involved cowpox virus, said Petersen, who is a medical officer in the CDC's Poxvirus and Rabies Branch.
In 4 of the 14 cases (29%), he added, "It was found that the strain . . . was other than the one the researcher thought they were working with," which demonstrates the uncertainty of the risks. He also noted that 18 of the 26 exposures involved recombinant viruses.
The information represents only the cases that were reported to the CDC or in the literature and therefore probably does not cover all those that have occurred, Petersen told CIDRAP News today.
Vaccinia virus, the active ingredient in smallpox vaccine, is used in laboratory research for such purposes as expressing genes from other organisms, Petersen noted at the meeting.
Because of the risk of infection for lab workers, the ACIP in 2001 recommended smallpox (vaccinia) vaccination for lab workers who handle cultures or animals contaminated with vaccinia virus that is not highly attenuated, Petersen explained.
He reported that 7 of the 26 reported exposures involved workers who had been vaccinated in accordance with ACIP recommendations, and only 1 of those 7 became infected.
ACIP member Lee Harrison, MD, who chairs the ACIP's smallpox vaccine work group, said the smallpox vaccine protects against all orthopoxviruses, including vaccinia. He said the work group was set up last year to review the requirements for working with orthopoxviruses.
Harrison, a professor of medicine and epidemiology at the University of Pittsburgh, said the review is deemed necessary because the ACIP has not updated its recommendations since 2003. In 2007, the smallpox vaccine ACAM2000 was licensed, and it has since replaced the Dryvax vaccine in the US national stockpile.
Petersen said the CDC is comparing data on ACAM2000 and Dryvax to assess whether ACAM2000 should be routinely recommended for persons at risk for orthopoxvirus infections. He said the smallpox vaccine work group hopes to present updated recommendations at a future ACIP meeting.