The results of the test on monkeys were so good that a human trial has begun to see if it can be a vital weapon in the war on HIV.

An experimental vaccine has prevented HIV infection in half of the monkeys that received it in a recent trial, and tests will be conducted on humans to see if scientists have really discovered the best tool yet that could lead to the eradication of the disease.

In the most recent tests, monkeys were given the vaccine and then subjected to high doses of an aggressive virus that is considered a simian cousin to HIV, which leads to AIDS, according to a Daily Mail report.

The results were astonishing: about half of the monkeys were protected from the virus, and now Johnson & Johnson is stepping in to begin a trial in 400 healthy volunteers spread out in Thailand, the United States, and East and South Africa. It’s the first time a major pharmaceutical company has sponsored efforts to develop an HIV vaccine since Merck failed to get the necessary results in a 2007 trial.

A total of 35 million people have HIV in the world. The disease first began spreading 30 years ago, and it is believed that 40 million have died from the disease.

While treatment has been getting better allowing those with AIDS and HIV to live longer lives, scientists believe that if they want to eradicate the virus, the best chance is through vaccines.

This two-step vaccine essentially primes the immune system. First, a weakened version of the cold virus is injected. In the second phase, purified HIV surface proteins are injected to provoke a strong immune response. It’s similar with how scientists are battling the Ebola virus.

Scientists were especially aggressive in the HIV vaccine trial with the monkeys in order to test the limits of the vaccine.