Why is smallpox vaccine effective even when its given shortly after exposure?
The data are pretty clear that vaccination within a few days of exposure to smallpox has a dramatic impact. It is a unique situation; maybe the only vaccine that works this way. The pathogenesis of smallpox involves a long incubation period. Infection occurs by inhalation, which gives primary replication in the oral pharynx. Then there’s a viremic spread that seeds the skin. During this period, the patient is asymptomatic. Finally there’s viral replication in the skin, which produces the serious illness. But the vaccine grows a lot faster–when vaccinia is injected into the skin, it immediately starts an infection. The cellular response begins very quickly, although antibody doesn’t come up very fast. There’s also a lot of attention now on anthrax vaccines. What is being done? NIH recently gave two contracts for the rapid development of a second-generation anthrax vaccine, which will be a recombinant vaccine against the so-called protective antigen of anthrax [a protein that helps anth
