[NAIROBI] Trials of a vaccine against the most common cause of pneumonia and meningitis — both leading causes of death in HIV sufferers in Africa — have proved so successful that scientists say it could be a major breakthrough in combating the diseases.
The new vaccine protects against Streptococcus pneumoniae which causes pneumonia and, when it invades the bloodstream and brain, causes septicaemia and meningitis.
Adults in the United Kingdom and the United States are given a polysaccharide vaccine but, because it does not work well in HIV-infected adults, it is not recommended in Africa.
The new conjugate vaccine was tested using nearly 500 HIV-infected adults who had recovered from a bout of pneumococcal disease. Three quarters of the patients remained free from the disease, according to the researchers at the Malawi-Liverpool-Wellcome Trust Clinical Research Programme, based at the University of Malawi College of Medicine.
The vaccine worked even when the number of CD4 cells in a patient's blood — an indicator of immune strength — was less than 200, the level that indicates AIDS.
Unlike the polysaccharide vaccine the new conjugate vaccine contains a protein that helps the body’s immune system recognise the pneumococcus bacteria, said Neil French, of the Liverpool School of Hygiene and Tropical Medicine, in the United Kingdom, lead author of the study.
"The general view on the use of any vaccine in HIV is that low CD4 counts make the vaccine useless. We've shown that conjugate technology overcomes the profound immune deficiency at these low counts. This gives hope for the possible use of conjugate technology in other vaccines targeting important HIV associated bacterial infections, most notably non-typhoidal Salmonella," he said.
"If conjugate vaccines are found to confer protection against invasive pneumococcal disease, this will be a major breakthrough, to reduce the morbidity and mortality of HIV infected persons from pneumococcal disease," said French.
Jeremiah Chakaya, a chest specialist at the Kenya Medical Research Institute welcomed the vaccine but said it will only be a breakthrough when the price — US$40 — is brought down.
"If the cost of the conjugate vaccine is about US$40 per dose, then it is going to be very difficult for most African governments to purchase it, and even if they do, then the people who need it will have to buy it at a very high price. This would make the vaccine a preserve of the few rich people in the countries."