Immunization, Vaccines and Biologicals


HIV/AIDS is a disease caused by the Human Immunodeficiency Virus (HIV), which targets the immune system and weakens people's surveillance and defense systems against infections and some types of cancer. As the virus destroys and impairs the function of immune cells, infected individuals gradually become immunodeficient. Immunodeficiency results in increased susceptibility to a wide range of infections and diseases that people with healthy immune systems can fight off.

HIV can be transmitted via the exchange of a variety of body fluids from infected individuals, such as blood, breast milk, semen and vaginal secretions but not by ordinary day-to-day contact such as kissing, hugging, shaking hands or sharing personal objects, food or water. The symptoms of HIV vary depending on the stage of infection. Though people living with HIV tend to be most infectious in the first few months, many are unaware of their status until later stages. The first few weeks after initial infection, individuals may experience no symptoms or an influenza-like illness including fever, headache, rash or sore throat. As the infection progressively weakens the person's immune system, the individual can develop other signs and symptoms such as swollen lymph nodes, weight loss, fever, diarrhoea and cough. Without treatment, HIV/AIDS invariably leads to the death of the infected individual.

There is currently no vaccine against HIV/AIDS. However, there are a number of very encouraging leads towards the development of a HIV vaccine. Thus, a combination of two vaccines, a modified poxvirus expressing HIV antigen and a so-called protein subunit vaccine, was shown to provide over 30% protection against HIV infection in a human clinical trial, the “RV144 protocol”, in Thailand, in 2009. The current vaccine development effort is therefore two-pronged: to improve on the results of the RV144 protocol, in trials planned in Thailand and South Africa and to develop a whole range of “second generation” products to address challenges such as the extreme variability of the HIV virus, which is recognized as an important bottleneck to HIV vaccine development.

In the absence of a licensed vaccine, WHO recommends prevention of HIV infection through:

  • male and female condom use,
  • testing and counselling for HIV and Sexually Transmitted Infections,
  • voluntary medical male circumcision,
  • anti-retroviral (ARV) drug-based prevention, including pre- and post-exposure prophylaxis,
  • harm reduction for injecting drug users and (f) elimination of mother-to-child transmission of HIV.

The development of an HIV vaccine is a high priority and WHO supports this effort through technical guidance and advice.

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Last updated: 27 January 2014