The worldwide eradication of smallpox may, inadvertently, have helped spread HIV infection

Experts say the vaccine used to wipe out smallpox offered some protection against the AIDS virus and, now it is no longer used, HIV has flourished. The investigators said trials indicated the smallpox jab interferes with how well HIV multiplies. Smallpox immunization was gradually withdrawn from the 1950s to the 1970s, following the worldwide eradication of the disease, and HIV has been spreading exponentially since then. The smallpox vaccine appeared to cut HIV replication five-fold.