THE EDITOR, Sir:

We are writing to address some of the issues raised in two recent Letters to the Editor in relation to HIV vaccine trials in Jamaica. Contrary to what was stated, the experimental vaccines do not use any part of whole or live HIV and cannot cause HIV or AIDS.

The vaccines have synthetic copies of small parts of the virus that stimulate the person's immune system to produce antibodies orwhite blood cells (T cells) that fight HIV infection.

Three phases of testing

Clinical trials are essential in order to determine the safety and effectiveness of any new vaccine or drug. New HIV vaccines must go through three phases of testing:

Phase 1 involves a small number of persons and determines the safety of the vaccine.

Phase 2 involves hundreds of persons and determines how the vaccine works within the immune system and studies safety issues more carefully.

Phase 3 involves thousands of persons over several years and determines the protective benefits of a vaccine against HIV and AIDS.

Jamaica is one of several countries involved in testing vaccines to prevent HIV and is currently participating in phase 2 clinical trials. The experimental vaccines used in these trials have gone through animal testing and phase 1 trials, and the vaccines have been found to be safe for use in clinical trials. Safety information is collected at every phase of testing and continues to be collected even after a vaccine or drug is approved for public use.

All volunteers for HIV vaccine trials must be healthy and HIV-negative. At each clinic visit, volunteers receive risk-reduction counselling and condoms. They are encouraged to practise safe sex in order to avoid exposure to HIV.

Unfortunately, some persons with high-risk sexual behaviour do not change their behaviour despite extensive counselling and may become infected during the course of a trial. We will know if the vaccine is effective, if fewer persons receiving the vaccine are infected during the course of the trial when compared to those receiving a placebo (saline without vaccine).

Legitimate study

The HIV vaccine trials in Jamaica are part of the HIV Vaccine Trials Network (HVTN), which has more than 25 study sites on four continents. The vaccine trials follow international guidelines for ethical conduct of clinical trials and all study materials are approved by local ethics committees (Ministry of Health, Jamaica and University of the West Indies). These materials and the activities of the Vaccine Trial Unit are also reviewed by a Community Advisory Board which consists of members of the community.

The recruitment process includes a detailed informed consent procedure in which volunteers are given information on the vaccines, potential risks and benefits. Volunteers can withdraw from a clinical trial at any time.

For further information on the HIV vaccine trials contact the Epidemiology Research and Training Unit at 55 Slipe Pen Road (922-4873 or 922-4461) or visit the HVTN website at www.hvtn.org.

I am, etc.,

PROF. PETER FIGUEROA

Chief, Epidemiology & AIDS

Principal Investigator

Dr. JACQUELINE DUNCAN

Co-investigator

Ministry of Health

Health Promotion & Protection Division