What is a vaccine and how does it work?

Millions of lives, across the world, are saved each year because of a small but powerful collection of 10-20 different vaccines. These protect both children and adults from a whole range of otherwise life-threatening diseases like diphtheria, tetanus, measles, rabies, hepatitis, influenza, meningitis and yellow fever. Without vaccines, we would still be battling polio on a global scale and would still be living in fear of small pox across India. Vaccines are among the safest and most cost-effective public health tools that have shaped human well-being as we know it today.

A vaccine works in a seemingly simple manner. The human body has a built-in mechanism to fight disease, which is called the immune system. In normal course, an individual’s immune system learns how to protect him/her against a disease only after the body is exposed to the disease or infection once. But a vaccine stimulates the immune system to recognise the disease/infection in advance, by teaching the immune cells to identify certain invaders, such as germs, that cause disease. These lessons of being able to distinguish invaders are then stored by the memory of the immune system, so that it quickly responds the next time the body is exposed to the same risk. To put it simply, vaccines allow humans to not leave the important job of fighting infection to chance and prime the body to take charge and keep dangerous diseases at bay.

Is there a vaccine against AIDS?

Currently, there is no effective AIDS vaccine available, but the need for one is urgent because it remains the best long-term hope to bring an end to the AIDS epidemic. The scientific search for such a vaccine is almost as old as the discovery of HIV and AIDS, but developing a safe and effective AIDS vaccine is turning out to be a bigger challenge than other vaccines.

Many common vaccines are based on killed or weakened versions of the germ which causes the disease against which they build protection. No one is looking at vaccines of this type against HIV. All of the AIDS vaccines which are being tested in humans are based on a new way of making vaccines: scientists take tiny, harmless bits of HIV and hide them inside common germs that we know the body can recognise. There is no way that such vaccines can cause infection. Researchers hope that the body will find the hidden fragments and then learn to recognise HIV if it tries to attack the body.

Several candidate AIDS vaccines are in various stages of being tested in the laboratory, animals and humans. It is a long and tedious process but there is sufficient evidence to believe that an effective AIDS vaccine is a scientific possibility.

Most vaccines in use today are designed to protect humans from disease or infection, i.e. they are preventive vaccines. Most scientific efforts in the search for an AIDS vaccine are also focussed on finding a preventive AIDS vaccine. A preventive AIDS vaccine will be meant only for people who are not infected with HIV, for it will prepare the immune system to respond in case of exposure to the virus. All references in this document are to a preventive AIDS vaccine.

	WHAT ARE THERAPEUTIC AIDS VACCINES ? There are scientists who are working to develop therapeutic AIDS vaccines too. These are designed for people who are already infected with HIV and an ideal therapeutic vaccine will teach the immune system to control HIV in the body and prevent progression of infection to disease. Therapeutic vaccine research is still in its early stages of development.

How is an AIDS vaccine developed?

AIDS vaccines are tested in various stages over several years, as with most other vaccines. Initial laboratory work is followed by animal studies and then human clinical trials. Many of the modern, licensed vaccines that are used today have taken several decades before they cleared the many complicated stages of their development. Experts believe a safe and effective AIDS vaccine may be found within the decade, but there are others who feel it may take much longer than that.

In keeping with international regulatory requirements, a vaccine clinical trial has three phases:

If the vaccine is found to be safe and effective, it may be licensed for widespread public use by the Drugs Controller General of India. It would then be available for use in the community.

Is it necessary to test an AIDS vaccine in humans?

Any vaccine has to be tested in humans to make sure that it does not cause side effects and that it works. After initial laboratory work and animal testing, human trials provide conclusive results on whether the vaccine is successful in protecting against the infection or disease and poses no danger to the human body. The necessity of testing AIDS vaccines in humans is even stronger because:

HIV is a virus that exclusively infects and causes disease in human beings;

There are no good animal models that can mimic what happens in the human body because our immune system is very different; although animal model data provide insights into vaccine concept and design, and reassurance about safety, only human clinical trials can determine whether the vaccine actually works the way it is supposed to (vaccine efficacy).

Why does India need to participate in AIDS vaccine trials?

India today is a strong global partner in the worldwide quest for a safe and effective AIDS vaccine for the world. Indian scientists and top Indian medical research institutions are collaborating with international partners to develop a preventive AIDS vaccine. Multiple vaccine candidates are being considered for testing in India . Development and deployment of an AIDS vaccine for India would require participation by the people in testing out the vaccine. Clinical trials in humans are already underway in many other countries to test AIDS vaccine candidates.

Are there other countries conducting AIDS vaccine trials?

Since 1987, more than 40 different AIDS vaccines have already been tested in over a 100 clinical trials. These trials have taken place or are ongoing in many countries across the world including Australia , Belgium , Botswana , Brazil , Canada , China , Cuba , Finland , France , Germany , Haiti , Kenya , Malawi , Peru , Puerto Rico , South Africa , Switzerland , Thailand , Trinidad and Tobago , the United Kingdom , the Netherlands , Uganda , and. USA . More than 15,000 volunteers have participated in such clinical trials worldwide.

Are there plans to conduct AIDS vaccine trials in India?

India's first-ever clinical trial of a preventive AIDS vaccine began in February 2005 at the National AIDS Research Institute (NARI) in Pune, Maharashtra, after obtaining all ethical and regulatory approvals from the Government of India. The vaccine candidate being tested for safety and imunogencity at NARI is tgAAC09 (AAV).

The second Phase I trial is scheduled to begin shortly at the Tuberculosis Research Centre (TRC) in Chennai, Tamil Nadu. The approval process for the second candidate,TBC-M4 (MVA), to be tested at TRC is also complete..