VOA常速英语:New TB Vaccine Passes Safety Tests

Tuberculosis continues to be a major threat around the world, especially in developing countries. A new vaccine has gone into testing, and the results may change how childhood vaccinations are given.

TB kills 1.8 million people a year. The current vaccine for tuberculosis, called BCG, is normally given to newborns in countries where TB is a major threat.

The vaccine is very effective in children, but experts seeing a rise in adult TB cases think the vaccine's protection may eventually wear off. So the hunt has been on for a stronger, longer-lasting vaccine.

In response, researchers at Oxford University in England came up with a vaccine supplement called MVA85A. Preliminary tests indicate that, when given to children who also received the old vaccine, it is safe and produces a robust immune response, which is what a vaccine is supposed to do.

That conclusion came from a study of several hundred infants in Gambia, which also helped researchers learn the best way to administer the new vaccine.

One group of infants got the new vaccine along with their other childhood immunizations. Another group got the TB vaccine separately. Dr. Martin Ota of the Bacterial Diseases Program in Banjul, Gambia, says the two groups responded differently to the TB vaccine.

The children who got all the vaccines together had a lower immune response to the TB vaccine than those who got the TB vaccine separately, "Which implies that giving these two groups of vaccines together has a negative impact on the new TB vaccine."

Ota is the lead author of a paper describing the study.

He explains that although the measured tuberculosis immune response was lower when the TB vaccine was given with the other vaccines, it still may be enough to protect against the disease.

"We don't really know what the level that provides protection is. It might be that it is good enough, but we haven't reached that stage," Ota says in a video posted on the website of the journal Science Translational Medicine, which published his paper.

In the paper, the authors say that the lower immune response when the vaccines are given together is more likely a result of interference between adjuvants, which are additives used to boost the effectiveness of a vaccine.

There are benefits in giving all the vaccines together, including fewer clinic visits and higher vaccination rates, but for now,  Ota says, the results of his study suggest that the new TB vaccine should be given separately.