Sexual Health Buzz

The trial of a much-anticipated new HIV vaccine was suspended last week, following a review by an independent monitoring board that deemed the vaccine ineffective. The suspension of the phase II clinical trial of Merck & Co.’s investigational HIV vaccine (V520), in development for a decade, marks a setback in the global effort to combat the worldwide HIV epidemic.

The trial, called STEP, was an international phase II “test of concept” trial in uninfected volunteers at high risk for acquiring HIV infection. It intended to test both whether the vaccine would help prevent the occurrence of new HIV infections as well as reduce the amount of virus in those who developed infection. The trial enrolled 3,000 HIV-negative volunteers from areas of North and South America, the Caribbean, and Australia between 18 and 45 years of age. A planned interim efficacy analysis conducted in approximately 1,500 volunteers revealed the disappointing results.

The vaccine did not prevent infection. In volunteers who received at least one dose of the three-dose vaccine series, 24 cases of HIV infection were observed in the 741 volunteers who received vaccine, while 21 cases of HIV infection were observed in the 762 participants in the placebo group. In the subgroup who had received at least two vaccinations and who were HIV negative for at least the first 12 weeks of the trial, 19 cases of HIV infection were observed in the 672 volunteers who received vaccine and 11 cases were observed in the 691 volunteers who received placebo. In addition, the vaccine did not reduce the amount of virus in the bloodstream of those who became infected; HIV RNA levels approximately 8 to 12 weeks after diagnosis of infection were similar in the vaccine and the placebo arms.

Though the results are disappointing, researchers have stated that there are many other trial vaccines currently being tested, as well as some that are soon to go into testing. This is promising, due to the fact that different vaccines stimulate different types of immunity. “It isn’t the end of the line,” said Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition, a New York group advocating prevention. Merck’s data “aren’t the answers we wanted, but they will help improve our other vaccine candidates.”

This information brought to you by the American Social Health Association and presented strictly for educational purposes.