1. Africa's victory, Africa's sorrow

2. A tough challenge

3.Multiple proteins

4. Immune-system helper

5. Making sense of vaccines

Three mothers gaze at the camera in Zuiginchor, Senegal. The battle against the AIDS epidemic has been more effective in Senegal than most African countries.
© David Tenenbaum

Once the virus has been defeated, a few cells specifically targeted to that infection linger, ready for the next infection. These "memory cells" explain why you normally can't get chicken pox twice.

Although the immune system is smart, it sometimes needs an introduction -- via a vaccine -- to its enemies. Vaccines "prime" the immune system with a glimpse of the enemy -- say a part of a live virus, or a killed whole virus. You don't get sick, but your immune system "remembers" the pathogen with weapons ready to attack next time around.

Africa's AIDS belt. In these countries, more than 10 percent of people aged 15 to 49 are infected with HIV.

Vaccines are older than microbiology. Back in 1796, long before viruses were known, Edward Jenner, an English doctor, invented the smallpox vaccine. Eventually, in 1980, vaccine made smallpox the first and only disease ever eradicated.

In the 1950s, two vaccines banished the paralytic scourge of polio. These days, you can get vaccinated against measles, mumps, yellow fever, some forms of hepatitis, and a bunch of other diseases.

Why not AIDS?
Next to clean water, vaccines may be the most significant factor behind the steady, global improvement in public health -- the very improvement threatened by AIDS. Thus when the AIDS virus was identified in 1984, federal officials predicted a vaccine would be ready for testing in two or three years (see "Shots in the Dark" in the bibliography).

Not exactly. Instead, AIDS vaccine research fumbled for a decade:

Vaccines that worked in lab dishes failed in animals.

Vaccines reduced virus numbers without preventing infection.

Rapid mutations in HIV raised the possibility that many vaccines might be needed for complete protection.

The vaccine market -- largely poor people in Africa and Asia -- did not interest bottom line-conscious investors and big drug companies. Far more profitable was the search for AIDS drugs, which must be taken day after day.

As time passed and AIDS-prevention failed, particularly in Africa, HIV became the best-studied virus in history. Problems with vaccines were due to the shifty, malign HIV, which:

Attacks the immune system, the body's defense against disease,

Hides in the body, even from powerful drugs, and

Mutates constantly, making an elusive target.

Save Your Generation Association is an Ethiopian self-help initiative run by young people. The goals are to improve living conditions and prevent unwanted pregnancies and sexually transmitted diseases, including AIDS. In December, 1999, 11 percent of Ethiopians aged 15 to 49 had HIV. Courtesy: German Foundation for World Population

Better late than never
Seventeen years after the AIDS virus was identified, no vaccine is on the market or in advanced clinical trials. Vaccine progress has been much too slow and too chaotic.

Today, spurred by the relentless growth of the epidemic and new discoveries in immunology, vaccine research is arising from the ashes. With luck, effort and money, we might see an AIDS vaccine -- or a therapy that prevents immune collapse -- in a decade or less. Or maybe never.

Are there some promising vaccines and related immune therapies?