A vaccine could cut tuberculosis cases among HIV-positive Africans by almost two-fifths, a U.S. study suggests.
The lung infection is the most common cause of death among HIV patients in the continent.
The journal AIDS reports that Dartmouth Medical School research involving 2,000 people found significantly fewer TB cases in vaccinated patients, BBC News reported Jan. 30.
An expert said the vaccine could be a cheaper option for countries struggling to find money for extra anti-HIV drugs.
HIV patients are particularly vulnerable to TB because their immune systems are compromised.
The Mycobacterium vaccae, or MV vaccine, works by boosting the immune responses of patients who have already been given the traditional Bacillus Calmette-Guérin TB vaccine earlier in life.
It was tested in 2,013 HIV outpatients in Dar es Salaam, Tanzania, who were vaccinated with the traditional TB vaccine (called Bacillus Calmette-Guérin, or BCG) shot as children. Participants were followed every three months for an average of 3.3 years.
In itself, the BCG vaccine may offer some protection against TB, but this is far from certain, and protection may only last a few years after immunization.
The number of confirmed TB cases was 39 percent lower in the vaccinated group.
Professor Ford von Reyn, who led the study, said it was a "significant milestone."
One theory now suggests that patients could be given the booster jab as soon as they are diagnosed with HIV, before antiretroviral drugs are needed.
Alvaro Bermejo, executive director at the International HIV/AIDS Alliance, said that the other way of fighting TB in HIV patients might be to give them antiretrovirals earlier, an expensive option compared with a vaccination program.
He said, "This is a very important finding — it is the first time we are going to have a vaccine which is influential in preventing opportunistic infections in HIV patients.
"TB is a massive problem — a third of people living with HIV in Africa are infected with it.
"The reduction of 39 percent seen in Tanzania, although not fabulous, is a good result."
The National Institute of Allergy and Infectious Diseases funded the seven-year study.