One Shot May Someday Replace Six for Rabies

WEDNESDAY, Sept. 23 (HealthDay News) -- An experimental rabies vaccine that may require only one injection produced promising results in animals, U.S. researchers report.

Currently, people exposed to rabies have to undergo six shots over 28 days -- five injections of the rabies vaccine and one injection of rabies immunoglobulin.

The new replication-deficient rabies virus vaccine lacks a key gene called the matrix (M) gene, according to a news release from Thomas Jefferson University, where the research was performed.

"The M gene is one of the central genes of the rabies virus, and its absence inhibits the virus from completing its life cycle. The virus in the vaccine infects cells and induces an immune response, but the virus is deficient in spreading," James McGettigan, an assistant professor of microbiology and immunology at Jefferson Medical College at the university in Philadelphia, said in the news release.

The immune response triggered by the vaccine is so strong that a single injection may be sufficient to protect a person who has been exposed to rabies, usually through being bitten by a rabid animal. The vaccine produced a rapid and efficient anti-rabies immune response in mice and non-human primates. The vaccine also appears to be efficient when used both before and after exposure to rabies, according to the research, which was published online Sept. 18 in the Journal of Infectious Diseases.

Worldwide, rabies kills between 40,000 and 70,000 people each year. Rabies is endemic in developing regions, where the six-shot anti-rabies regimen isn't feasible for many people due to cost and availability. Each year, about 10 million people undergo the post-exposure regimen, according to the World Health Organization.

"Developing countries do not have the resources to vaccinate people six times after exposure, so many of these 10 million do not receive the full regimen," McGettigan said. "Therefore, simpler and less expensive vaccine regimens are needed. The alternative may also be to treat people pre-exposure, as they are with many of the current vaccines used. Although our vaccine was tested primarily to be a post-exposure vaccine, the data we collected show it would be effective as a pre-exposure vaccine as well."

-- Robert Preidt

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SOURCE: Thomas Jefferson University, news release, Sept. 21, 2009