Dengue Vaccine Undergoing Clinical Trials in Puerto Rico

by VR Sreeraman on Aug 17 2007 4:11 PM

A vaccine designed to immunise people against four strains of dengue fever transmitted by the Aedes aegypti mosquito is undergoing clinical trials in Puerto Rico and could be on the market within a few years.

If the current round of testing is successful, the vaccine could be the answer for the illness that affects millions of people in the world's equatorial regions. So far this year, dengue has taken the lives of at least 22 people in Central America, Mexico and the Caribbean.

One of the doctors participating in the investigation, Javier Morales, Wednesday said that the first effective vaccine against the four types of dengue successfully passed laboratory tests using animals. It also passed a first phase of testing with humans during which it was administered to 30 people, reported Spanish news agency EFE.

The first time that a person is infected with one of the four types of dengue, he acquires classical dengue. Despite the fact that he will never suffer from the same strain of the disease again, he can contract the other three types.

If the person is infected again he could suffer hemorrhagic dengue, which can be fatal.

After the US Food and Drug Administration (FDA) approves the first experiments on dose size and toxicity, the vaccine will be given to 720 people to test its statistical effectiveness.

The GlaxoSmithKline pharmaceutical firm and the US Army's Walter Reed Hospital are developing the vaccine along with five other US institutions.

Morales said that although vaccines have been developed to treat specific types of dengue, none has yet been developed to impart permanent immunity to patients.

Last month, researchers began vaccinating a new group of patients in San Juan who range in age from seven months to 50 years. The patients must be healthy and if they are women they must not be pregnant or have the intention of becoming pregnant within the next year.

After the vaccine is administered, researchers take blood samples from the patients to analyse the immediate creation of antibodies and if 'immunological memory' has been developed. This is done with an eye toward determining whether the antibodies will continue to be active over the short and long term and if booster shots will be necessary.

Morales said that he was hopeful that after administering a second dose six months later and presenting the results to the FDA it would pre-approve the vaccine for 'thousands of people' before it goes on the market, although the process could take several years.