Because of this, scientists have been searching for a vaccine ‘€“ that one magical injection that could protect us from HIV no matter how risky our sexual behaviour.
They’€™ve been at it for 25 years now, and while a single magical vaccine isn’€™t going to happen any time soon, the world finally has a range of options to prevent HIV.
The list goes something like a hit parade, with six new ‘€œhits’€.
Antiretroviral medicine is top of the pops. It may seem nonsensical that pills designed to treat a virus are being hailed as a preventive measure.
But recent research on over 1 700 couples where one partner was HIV positive and the other negative, found only four percent of the HIV negative partners got HIV if their positive partner was on three ARVs. This was because ARVs reduced the level of virus in the infected person’€™s blood, making them less infectious.
The new buzz phrase now is ‘€œtreatment as prevention’€.
Hit Number Two is another ARV-based protective measure. Three studies of people taking ARV pills before they had risky sex (pre-exposure prophylaxis) showed a protective range of between 44 and 73 percent.
The third most successful preventive measure relies on more pills, but not ARVs. When people are treated and cured of other sexually transmitted infections, over four in ten (42 percent) are protected from HIV, as this eliminates the genital cuts and inflammation that make it easy for HIV to enter humans.
Success story four does not rely on a pill but on the snip! Male circumcision cuts the rate of HIV infection by 60 percent as a man’€™s foreskin provides a moist haven for the virus and easy access to a man’€™s body.
Coming in fifth is the recently tested vaginal gel based on the ARV called tenofovir. This protected almost four out of ten women (39 percent) from HIV.
Finally, at number six is the Thai vaccine known by the rocket-like name of RV144, which protected 31 percent of those who were given it from HIV.
‘€œWe are currently in the most optimistic era of HIV prevention,’€ said Dr Carl Dieffenbach from the US National Institutes of Health.
‘€œFor the first time, we have tools to start to control the HIV epidemic and we are also close to developing an effective, safe and durable vaccine.’€
‘€œClose’€ is a relative word, of course. HIV is an ever-changing (mutating) virus, which is why some describe it as a ‘€œmoving target’€.
Because it is so tricky, it has been necessary for scientists to observe the tiniest of reactions in human cells to HIV.
The outcome is recorded in an often-bewildering array of papers at this year’€™s International AIDS Vaccine Conference, which describe the complicated dance between HIV and the many cells that make up the human immune system.
Researchers are grappling with a wide variety of challenges, including how to ‘€œtrain’€ antibodies to prevent HIV from getting inside our cells to encouraging our defender (CD4) and killer (CD8) cells to identify and kill HIV.
About one in five people infected with HIV are able to ward the virus, and they are under the microscope as scientists try to understand why their immune systems can fight HIV more successfully than most.
The moderately successful Thai RV144 trial is being taken apart, piece by painstaking piece, to try to understand how it worked.
The only ‘€œclues’€ so far are two antibodies found in the blood of those involved in the trial.
The one antibody was high in those that didn’€™t get HIV and it attached itself to the same parts of the virus every time, suggesting that it could recognise the virus.
The other antibody had the opposite effect, being high in those infected and low in those not infected.
For non-scientists, it may seem that this research is insignificant. But close collaboration between scientists through unique global organisations such as the HIV Vaccine Trials Network is ensuring that research is prioritised with money going to the most urgent and promising research, and results are shared.
Money is always a problem, even more so given the global recession, and lack of funds poses a serious threat to the fight against HIV.