Vaccination
Administration of a vaccine for either preventive or therapeutic purposes.
See Also:   Vaccine
                   Preventive HIV Vaccine
                   Therapeutic HIV Vaccine

Vaccine
A substance that stimulates the body’s immune response in order to prevent or control an infection. A vaccine is typically made up of some part of a bacteria or virus that cannot itself cause an infection. Researchers are testing vaccines both to prevent and treat HIV/AIDS; however, there is currently no vaccine approved for use outside of clinical trials.
See Also:   Preventive HIV Vaccine
                   Therapeutic HIV Vaccine

Vaccinia
A cowpox virus that is used as a vaccine against smallpox infection and as a vector, or carrier, for other types of vaccine. In HIV vaccine clinical trials, vaccinia and other herpesviruses have been used as vectors.
See Also:   Vector
                   Herpesviruses

Varicella Zoster Virus (VZV)
A virus in the herpes family that causes chicken pox (usually during childhood) and may reactivate later in life to cause shingles.
See Also:   Herpesviruses
                   Shingles

VAT
See: Visceral Adipose Tissue

Vector
A harmless virus or bacteria used as a vaccine carrier to deliver pieces of a disease-causing organism (such as HIV) into the body’s cells in order to stimulate a protective immune response.
See Also:   Vaccine

Vertical Transmission
A term used to describe the transmission of a disease from parent(s) to offspring. For example, HIV can be spread vertically from mother to child during pregnancy, at birth, or through breastfeeding.
See Also:   Mother-to-Child Transmission
                   Horizontal Transmission

Viral Load (VL)
The amount of HIV RNA in a blood sample, reported as number of HIV RNA copies per mL of blood plasma. The VL provides information about the number of cells infected with HIV and is an important indicator of HIV progression and how well treatment is working. The VL can be measured by different techniques, including branched chain DNA (bDNA) and reverse transcriptase-polymerase chain reaction (RT-PCR) assays. VL tests are usually done when an individual is diagnosed with HIV infection and at regular intervals after diagnosis.
See Also:   Branched Chain DNA Assay
                   Reverse Transcriptase-Polymerase Chain Reaction

Viral Load Test
Test that measures the quantity of HIV RNA in the blood. Results are reported as the number of copies of HIV RNA per mL of blood plasma. The two types of HIV viral load test are reverse transcriptase-polymerase chain reaction (RT-PCR) and branched chain DNA (bDNA).
See Also:   Viral Load
                   Reverse Transcriptase-Polymerase Chain Reaction
                   Branched Chain DNA Assay

Viral Rebound
Reappearance of HIV in the blood after having been successfully suppressed to undetectable levels following anti-HIV drug treatment.
See Also:   Undetectable Viral Load
                   Virologic Failure

Viremia
The presence of virus in the bloodstream.

Viricide
Any substance that can destroy or inactivate a virus.

Virion
A mature virus particle existing freely outside a host cell.

Virologic Failure
Inability of anti-HIV drug treatment to reduce viral load or to maintain suppression of viral load. Virologic failure is the most common type of treatment failure and may lead to immunologic and clinical failure.
See Also:   Immunologic Failure
                   Clinical Failure
                   Viral Load

Virology
The study of viruses and viral disease.

Virus
A microscopic organism that requires a host cell to make more copies of itself. Examples of human diseases caused by virus infections are AIDS, measles, mumps, rubella, polio, influenza, and the common cold.

Visceral Adipose Tissue (VAT)
A type of adipose (fat) tissue that surrounds internal organs in the abdominal cavity. Accumulation of this fat is known as central fat deposition or visceral lipohypertrophy, and may occur as a side effect of some anti-HIV medications, especially PIs and NRTIs.
See Also:   Subcutaneous Adipose Tissue

VL
See: Viral Load

VZV
See: Varicella Zoster Virus