After years of trying to drum up interest in a new anthrax vaccine, researchers learned last week that the U.S. government wants to buy one--in a hurry. The National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, announced 18 April that it is seeking bids to develop and test candidates. The Department of Health and Human Services plans to follow up with a contract to buy 25 million doses of the vaccine, to be added to the nation's emergency stockpile.
The only anthrax vaccine licensed in the United States today is a mixture of proteins produced by a tame form of Bacillus anthracis, the bacterium that causes anthrax. This anthrax vaccine adsorbed (AVA), as it's called, was developed in the 1950s and is used primarily by the military. It isn't ideal for general use, primarily because immunity builds up slowly. Vaccinees require a series of six shots over 18 months, followed by a yearly booster. Instead, NIAID wants a vaccine that requires no more than three shots and that would work so rapidly that it could be given after exposure to anthrax spores.
Researchers have been exploring many alternatives to AVA. But because speed is of the essence, says Carole Heilman, director of NIAID's division of microbiology and infectious diseases, NIAID has decided to consider only the most extensively tested type of new vaccine: those based on a protein in the bacterium's toxin complex called protective antigen (PA). This protein is part of the mélange present in AVA, and researchers believe that it is the main contributor to protection. Studies have shown that the vaccines made with this protein protect rhesus monkeys against inhalation anthrax; they also suggest that fewer injections are needed and that the vaccine might have fewer side effects than AVA.
Some researchers say the choice for injected PA is needlessly conservative, neglecting other, more promising approaches. "It's very disappointing," says Uma Ryan, CEO of AVANT Immunotherapeutics, a company in Needham, Massachusetts, that is developing an oral, one-dose anthrax vaccine. But others support NIAID's decision. "If we want to have something within a few years, recombinant PA is the way to go," says Stephen Leppla, an anthrax researcher at the National Institute of Dental and Craniofacial Research in Bethesda.
and ELIOT MARSHALL Related sites
General information about anthrax, from the Centers for Disease Control and Prevention
NIAID's request for proposals for the development and production of the new vaccine
Report by the Institute of Medicine about the safety and efficacy of AVA