For Some, Immunity to Smallpox Is Gone

Adults given smallpox vaccinations as children before the disease was eradicated in the mid-1970s have probably lost their immunity to the highly infectious disease, new research indicates.

“This study is, to the best of my knowledge, the only one since eradication which tries to look at the durability of immunity,” Michael Sauri, director of the Occupational Medicine Clinic in Maryland, told New Scientist magazine Wednesday.

“It’s showing us that after 20 years, immunity is not going to be there.”

The study of 621 microbiologists, who were vaccinated again from 1994 to 2001 because of the type of work they do, found that only about 40, or 6%, were still immune to the disease from the vaccinations they had received earlier.

The new research heightens the debate about whether pre-emptive mass vaccinations are needed or if “ring vaccination” of people in an affected area could contain an outbreak of the disease following a bioterrorist attack.

The Centers for Disease Control and Prevention in Atlanta favors limited vaccination because little is known about what determines long-term immu- nity.

But Bill Bicknell of Boston University, a former public health official, said he believes that selective mass vaccination may be the best policy because of the threat of the terrorist use of smallpox.

He said vaccination could minimize the impact of smallpox as a weapon and the risk to the general population.

“I am advocating vaccination of first responders--emergency workers, hospital workers, doctors, nurses and other staff and wider groups of people essential for the maintenance of civil society,” Bicknell said.

He suggested vaccinating about 100,000 emergency and hospital workers.

Then, he said, the side effects of the vaccinations should be studied and the situation reevaluated before deciding on expanding the program to more emergency workers and later to the public.