Eradicating smallpox linked to spread of HIV

The worldwide eradication of smallpox may have inadvertently helped to spread HIV.

Scientists believe the vaccine used to wipe out smallpox offered some protection against HIV, but its gradual withdrawal allowed the virus to flourish.

Smallpox is estimated to have killed up to 500 million people in the 20th century alone, but comprehensive vaccination programs succeeded in eradicating the disease.

In findings published in the journal BMC Immunology, scientists said HIV rates increased exponentially after the vaccine was withdrawn from use.

The US investigators say trials indicate the smallpox jab interferes with the way HIV spreads within the body.

They found replication rates of HIV in the blood cells of vaccinated individuals were five times lower compared to those without the vaccine.

But they say it is too early to recommend smallpox vaccine for fighting HIV.