Robert Gallo's HIV Vaccine Has a Long Way to Go Before We Know If It Works

The man who discovered HIV says he's developed a vaccine. It's still years away, if it works at all.

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Oct 14 2015, 4:50pm

Image: University of Maryland/Flickr

Robert Gallo, the man who helped discover HIV and AIDS, thinks he may have a vaccine that'll prevent people from getting it.

Gallo announced late last week that his vaccine will soon enter human trials. Some are casting this as a Michael Jordan-coming-out-of-retirement to save the team type situation, with Gallo cast as the person perfect to help eradicate the disease he discovered. That's a nice narrative (and maybe a flawed analogy on my part), but the truth is that Gallo hasn't gone anywhere. His vaccine has been in development for the last 15 years—these things take a lot of time.

There's often confusion about how new drugs and vaccines ultimately end up being approved by the FDA, which makes sense, because it's a complicated process. Here's how the testing process works, and here's what Gallo's news means.

Two previous vaccine candidates entered Phase III human trials; both of them "failed to confer protection against HIV

Before any drug or vaccine is tested, there's lots of basic research: HIV is identified, its mechanisms of infection and structure are studied, patient outcomes are studied as well.

Basic research is incredibly important to eventually finding new drugs, but basic research is also often hyped by both researchers (who have to prove their grants were worth it to their funders) and the media (who need to explain to readers what the possible applications for a finding are) as being direct antecedents to new treatments.

Eventually, a drug or vaccine is developed, and it's often tested on individual cells. Then come animal trials. If a vaccine works in mice or monkeys, it's also often promoted as being potentially viable in humans, though that's often not the case.

Successful animal trials don't always predict whether a vaccine will work in humans, but it's an important step on the road to eventual FDA approval: "We wanted more and more answers before going into people," Gallo told Science.

Gallo's work is exciting, but it's too early to get excited.

And now, here we are. Human clinical trials. Gallo's vaccine is entering what's known as a Phase I trial: 60 people will get the vaccine, and Gallo will simply monitor whether or not the vaccine is "safe," whether or not the human immune system responds to the virus, and whether or not there are any side effects. If people start getting sick or the immune system doesn't respond, the vaccine will likely hit a dead end.

If it's deemed safe, it'll move to Phase II trials. The vaccine will be given to a larger group of people and its efficacy will actually be tested. Does it prevent people from getting HIV at the "time of infection," as Gallo says it should? Phase II is when we should know if it at least shows promise.

Phase III tests are the last stop before FDA approval. It'll be given to large groups of people, probably all over the country. Its efficacy and side effects will still be studied. New drug effectiveness will be compared to existing treatments (and to a placebo). New vaccines will be tested to show whether they actually confer immunity to those who receive it.

This is all to say that, 15 years in, it's still very early for Gallo's vaccine. Two previous vaccine candidates entered Phase III human trials; both of them "failed to confer protection against HIV," according to the National Institutes of Health. Finally, in 2009, a combination of those two vaccines together in a third Phase III trial showed "modest preventative effect in humans."

The results of this trial were not enough to get FDA approval, and further research is ongoing. Other HIV "cures" have stumbled late in the approval process.

Developing a vaccine—especially for a virus that mutates as often as HIV—is hard. Gallo's work is exciting, but it's too early to get excited.