The promise of an effective HIV vaccine has always been just over the horizon, but more than 20 years after the identification of HIV,
vaccines remain far from implementation.

The two large HIV vaccine studies till date have shown no protective
effect.The latest is the Merck’s trial which not only showed that the
tested vaccine could not prevent HIV infection but also highlighted
some other findings:

1) The trial participants who received the vaccine showed the highest
risk of HIV infection in individuals who had had adenovirus infection
in the past. Adenoviruses most commonly cause respiratory illness.
they could also cause various other illnesses such as infection of
the GIT, eyes and skin depending on the type. Symptoms of respiratory illness caused by adenovirus infection range from the common cold syndrome to pneumonia and bronchitis

2)the trial also showed that the trial participants who had signs of
adenovirus infection, and were uncircumcised were at four times
greater risk of HIV infection if they received the vaccine compared
to circumcised men who had the adenovirus infection and were in the
placebo group. A vaccine study is still ongoing in Thailand and should be concluded in June 2009. A phase IIb HIV vaccine study known as the PAVE 100 study is still being planned to begin in 2008. While we have dissapintment in the field, more studies are still needed in order to improve understanding of the strengths and limitations of various HIV vaccines designs.

For the future, vaccine approaches would focus more on basic research without precluding clinical research. Currently, investment in
vaccine research comes overwhelmingly from the public sector and
foundations. Only one private company (Merck) has invested more than $10 million annually in vaccine research. Companies cite the current scientific uncertainty and the lack of incentives for conducting
phase II studies and investigating process development as barriers to entry to the field