November 18, 2002
The trial vaccine incorporates parts of four different HIV genes. These are drawn from subtype B, which is the most prevalent form of HIV in North America and Western Europe, as well as subtypes A and C, which are the most common types in Africa and Asia. The three types, or clades, account for about 90 percent of HIV infections worldwide.
"The idea behind this global vaccine candidate is to broaden the coverage of the vaccine," said VRC Director Dr. Gary Nabel. Early lab tests with animals have shown that immune response to any single HIV type was not diminished by combining protection against all three major types.
The history of vaccine development supports the concept of a combination vaccine, Nabel said. "If you look at the polio vaccine, it actually contains three different strains of the disease to cover the three different most prominent strains, so there's an important precedent for that concept." Nabel noted that the virus "is constantly mutating, and seems to be adapting to different populations. So the idea behind having this global vaccine is that we are trying to ... have a better chance of resisting the newer viruses that develop."
Even if all goes well throughout the clinical trial, the vaccine will not become available to the public for at least five years from now, Nabel said.
11.14.02; Alan Mozes