By: Sarah Connolly
There are several reasons why HIV is an elusive target for a vaccine, a few of which are described here. Nonetheless, scientists are working tirelessly to uncover and test new strategies that could one day lead to a successful vaccine against HIV.
The error-prone replication over many, many years has led to broader evolution of the virus into at least 9 distinct genetic subtypes. These vary regionally throughout the world, and can sometimes recombine into mixtures of two or more subtypes. This means that even if a vaccine was effective in one part of the world, it might not be as effective against other subtypes in other regions.
Safety is always top priority when designing a potential vaccine. Some vaccines are made using a live, weakened version of the pathogen, while others use parts of a dead pathogen to train the immune system to recognize key characteristics. Given HIV’s notorious reputation for mutating and rapidly evolving, a live vaccine is not the safest option since a weakened HIV virus could possibly evolve into a more harmful one, which is not the case for many other viruses. Therefore, much attention is focused on identifying key parts of the virus that are rarely mutated, or ‘conserved’, and using these as possible vaccine targets.
While there are many challenges to developing a vaccine for HIV, not all hope is lost. There are 4 HIV vaccine candidates currently in clinical trials, with several different strategies for protection, and some based on earlier vaccine trials that showed promising results. In addition to vaccines to prevent initial infection, scientists are exploring therapeutic vaccines which could be used to cure infected individuals, or reduce the amount of virus circulating in their body to levels that would limit transmission and extend the healthy years of life. Already available is a medication that can be taken by HIV-negative individuals to prevent becoming infected, called Pre-Exposure Prophylaxis (PrEP). While PrEP doesn’t have the effect of training your immune system to fight off the virus the way a vaccine might, it is an effective way for high-risk individuals to protect themselves in addition to other prevention strategies such as correct, consistent condom usage.
 GLOBAL HIV AND AIDS STATISTICS 2016,
 HIV STRAINS AND TYPES,
 Clinical Trials Search, Vaccine Research, HIV Preventive Vaccines,
 RV144 Trial,