Last fall, the Centers for Disease Control (CDC) made waves when it recommended a voluntary smallpox-vaccine program to be extended to U.S. civilians in 2004 as a defense against terrorism. But buried in the controversy was a footnote of interest to all HIVers: Nix the vax -- unless you have a confirmed exposure to smallpox! Why? Because the vaccine can cause life-threatening reactions in people with weakened immune systems. (HIV testing will be offered to those at risk.)

The vaccine is made from living (but usually harmless) vaccinia virus, which provokes an immune response similar to smallpox exposure. In HIVers, though, that response might be delayed -- or not happen at all. Then the vaccinia could spread bodywide and cause a mess of miseries like those seen in smallpox -- including scarring, sight loss, brain damage, toxic shock and death. Although the severity of your reaction likely depends on how badly your immune system is suppressed, no one can predict exactly how the vaccine will act in HIVers -- or whether getting inoculated while your CD4s are high could cause problems down the line.

Even scarier is the possibility that the immune-needy could get vaccinia from someone who has been vaccinated. Worst-case scenario? The smallpox vaccine may mean an entirely new order of contagious opportunistic infection (OI) that HIV docs have no experience treating. The current recommended antidote is Vaccine Immune Globulin (VIG), made from the plasma of vaxed people. Right now, though, the U.S. has only enough VIG for 600 to 800 cases.

On the bright side, test-tube studies hint that certain drugs, such as intravenous cidofovir (for CMV) and alpha interferon and ribavirin (for hepatitis), may pack some punch against smallpox and vaccinia. The best treatment, of course, may be effective suppression of HIV, the bug that bugs out the immune system in the first place. But, hey, don't panic: After all, Osama may go nuclear, the equal-opportunity destroyer -- or, best, he may never come at all.