FDA: Smallpox vaccinees should skip blood donation

Health care workers who are currently rolling up their sleeves for smallpox vaccine should skip the local blood drives for a while, the Food and Drug Administration (FDA) advises.

Smallpox vaccine consists of the live virus vaccinia. After a week or two, the vaccinee develops an immune response against vaccinia, and once the scab has fallen off at the "take" site, the vaccinia virus has been eliminated from the body. But because vaccinia is a live virus, it might be able to enter the bloodstream. Although early studies with a different vaccine virus demonstrated bloodstream infections in some vaccinees, no modern studies have been done to find out if vaccinia enters the blood of vaccinees during the active infection.

"Until we are sure whether or not this is the case, the FDA is taking this step as a prudent measure to prevent possible transmission of vaccinia to blood recipients," the agency said in a statement. "Unlike healthy people, some blood recipients who have immune system problems may be especially susceptible to severe, even life-threatening vaccinia infections."

The FDA’s new temporary blood donor deferrals for people who have received the smallpox vaccination are as follows:

1. For vaccinees without severe complications: Deferral until after the vaccination scab falls off, or 21 days, whichever is longer. Rationale: People who have been vaccinated may have live vaccinia virus until the immune response is complete (usually by 14-21 days), and until after the vaccine scab has fallen off. Vaccine scabs have been shown to contain infectious virus.

2. For vaccinees with severe complications: Deferral for 14 days after complete resolution of severe complications. Rationale: Rarely, vaccinated people develop more extensive infections that can last longer than usual and can be serious. These include localized and progressive spread of infection beyond the vaccination site that may involve the eyes or non-adjacent parts of the skin, as well as widespread infections that may affect internal organs including the brain. A physician would diagnose these conditions. Since in these cases, vaccinia levels in the body may be higher than after uncomplicated vaccination, we recommend deferral of donors for 14 days after complete resolution of these severe vaccine complications.

The FDA also recommends temporarily deferring blood donors who inadvertently acquired vaccinia infection from a vaccinee, as follows:

1. For symptomatic contacts of vaccinees, who have only localized skin lesions, and not severe complications: Deferral until after the scab(s) fall off. Rationale: Just like vaccinees, people who have inadvertent vaccinia infection of the skin may have live vaccinia virus in the body until the immune response is complete (usually by 14-21 days), and until after the scab(s) have fallen off. Vaccine scabs have been shown to contain infectious virus.

2. For symptomatic contacts of vaccinees with severe complications: Deferral for 14 days after complete resolution of severe complications.

3. Asymptomatic contacts of vaccine recipients do not need to be deferred.