80-year-old vaccine not enough to fight TB, researcher says

Although tuberculosis remains a global threat and a strengthening foe, the most effective vaccine against it is more than 80 years old.

Dr. Helen McShane of the Jenner Institute at Oxford University is leading a team working on an alternative that is in a Phase II-B clinical trial in South Africa.

“We believe this is the most exciting advance in the field of TB vaccines for over 80 years,” she said of the drug known as MVA85A.

“TB remains a very significant cause of mortality and morbidity throughout the developing world,” said McShane, who began doing research after seeing many patients in London with both tuberculosis and HIV.

“The geographical overlap between the HIV and TB epidemics has had a devastating impact, particularly in sub-Saharan Africa.

The WHO estimates that someone in the world is newly infected with TB bacilli every second. Among the 15 countries with the highest estimated TB incidence rates, 13 are in Africa.

Currently the most effective vaccine is Bacille Calmette-Guerin (BCG), which was developed in France in the early 20th century.

“BCG, when given at birth [as it is in the developing world], works reasonably well to prevent 'disseminated disease' and TB meningitis in children,” McShane said.

But it has its drawbacks, she added.

“BCG does not protect consistently against lung disease, in adults but also in children and infants. Hence the need for a better vaccine. The most effective way to control any infectious disease epidemic is with an effective vaccine.”

She said MVA85A is designed to enhance BCG and to be given “at a later point in time — either soon after BCG [in infancy] or later on [in adolescence].”

MVA85A enhances the level of cellular immunity — T cells — induced by TB.

“We hope it also improves the protective efficacy” of BCG, she said.

This is what researchers are testing in the Phase II-B trial, which will not have any results until 2011-12.

“This trial will hopefully show that the vaccine can protect people from getting TB and enable the global community to begin to control this devastating disease.”

She said the emergence of multidrug-resistant tuberculosis and extensively drug resistant strains, referred to as MDR-TB and XDR-TB respectively, “has made treatment of this disease harder.”