A Tricky Virus Over the past 25 years, a disease swept the world, killing an estimated 26 million people and infecting 33 million more. That disease is called acquired immunodeficiency syndrome, or AIDS.
AIDS is caused by the human immunodeficiency virus (HIV), which attacks the T cells that help the body fight infection. HIV is transmitted directly or indirectly by contact with body fluids.
Sexual contact is one method of direct contact. Contaminated needles are a method of indirect contact.

Failed Vaccines
Since AIDS was first identified in the 1980s, scientists have been working to develop an AIDS vaccine. In 1984, the secretary of the U. S. Department of Health and Human Services predicted that it would take two years to create the vaccine. However, scientists did not realize at the time that HIV has an uncanny ability to mutate quickly. Different strains of the virus are present in different people and within the same person over time.
Several AIDS vaccines have been developed over the years, but none has worked. The antibodies produced by the vaccines were unable to fight the virus because they did not recognize the newly mutated strains.
The Search Continues
Many people are disappointed by the failure to develop an AIDS vaccine. But scientists point out that it often takes decades to develop an effective vaccine. For example, the polio vaccine took nearly 50 years to develop. There is still no vaccine for malaria.
Scientists such as David I. Watkins stress that people should remain hopeful. In a recently published article, Watkins wrote, “Far from giving up, HIV vaccine researchers are gearing up for a renewed fight. We could never have imagined in [1984] how stubbornly this virus would resist traditional vaccine techniques, but we are a stubborn bunch, too, and given time, science will find a way to defend against HIV.”

Applying Critical-Thinking Skills
Distinguish: Do vaccines cause active or passive immunity? Explain.

Weigh: Do you agree with scientist David I. Watkins that an AIDS vaccine will be developed one day? Why?