Based on the results from phase 1 and phase 2a clinical trials that involved almost 400 healthy adults in Rwanda, South Africa, Thailand, Uganda and the United States, a phase 2b trial has been initiated in southern Africa to determine the safety and efficacy of the HIV-1 vaccine candidate in 2,600 women at risk for acquiring HIV. That trial started in the fall and is underway in 2,600 women across sub-Saharan Africa.
Tests on a new drug stopped two thirds of monkeys contracting a virus similar to HIV and boosted an anti-HIV immune system response in 400 healthy adults, according to the study in The Lancet.
"This is only the fifth HIV vaccine concept that will be tested for efficacy in humans in the 35+ year history of the global HIV epidemic", Barouch added.
Only one so far, RV144, yielded some protection. This immune response could protect the humans from the infection.
For the experiment, the researchers recruited 393 healthy (non-HIV infected) adults ranging in age from 18 to 50 from 12 clinics in East Africa, South Africa, Thailand, and the United States. The participants were treated in clinics in east Africa, South Africa, Thailand, and the U.S., and either received a placebo or one of seven vaccine combinations. They received 4 vaccinations through a period of forty-eight weeks.
The vaccine was developed by Janssen pharmaceuticals.
Previous HIV-1 vaccine candidates have typically been limited to specific regions of the world. The trial drug has been proven safe and effective while being used by humans and is advancing to the next stage of testing.
At this point, however, the researchers clarified that the positive results were not guaranteed yet that an HIV treatment is at hand.
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Some of the volunteers reported some side effects but the researchers said they were tolerable.
"The challenges in the development of an HIV vaccine are unprecedented, and the ability to induce HIV-specific immune responses does not necessarily indicate that a vaccine will protect humans from HIV infection".
"These results represent an important milestone", Barouch said when speaking with BBC News.
"This one is novel in many ways, so it is exciting, but we have a long way to go". Implementation of even a moderately effective HIV vaccine together with the existing HIV prevention and treatment strategies is expected to contribute greatly to the evolving HIV/AIDS response.
With 37 million people living with HIV/AIDS, and an estimated 1.8 million new cases each year, a preventative vaccine is urgently needed to curb this worldwide pandemic. Death toll is estimated now at a million deaths per year. Nearly 21 million people were receiving antiretroviral treatment by mid-2017. The virus is able to mutate to avoid the attack of the human immune system, so we can't develop immunity to it.
In that same year, some 1.8 million people were newly infected while 1 million had already died because of HIV-related complications.
Condoms are still at the frontline of efforts to prevent infection - mainly through sex and blood contact - though more and more people use ART as prophylaxis.
The latest results come ahead of the International Aids Conference to be held in Amsterdam from July 23 to 27.