Virus like particle (VLP)

Nanoscale structures made up of assembled viral proteins that lack viral genetic material and are therefore non-infectious.


The relative capacity of a pathogen to overcome body defenses and elicit symptoms.


A tiny organism that multiplies within cells and causes diseases such as chickenpox, measles, mumps, rubella, and hepatitis. Viruses are not affected by antibiotics, the drugs used to kill bacteria.

Virus Vector

A form of a virus used to deliver genetic material into a cell.

VLP vaccine

Vaccine made from virus like particle (VLP). VLPs contain repetitive, high density displays of viral surface proteins that present conformational viral epitopes that can elicit strong T cell and B cell immune responses. Since VLPs cannot replicate, they provide a safer alternative to attenuated viruses. Vaccines for Hepatitis B and human papillomavirus, are developed and FDA-approved.

Volume of distribution(Vd)

A pharmacokinetic parameter representing an individual drug’s propensity to either remain in the plasma or redistribute to other tissue compartments.

Vulnerable Subjects

Groups of people whose range of options is severely limited, who may be subjected to coercion or who may be compromised in their ability to give informed consent to receive medical or surgical treatments or to participate in research. This includes pregnant women and fetuses, minors, prisoners, persons with diminished mental capacity, and those who are educationally or economically disadvantaged.


Cowpox is an infectious disease caused by the cowpox virus. Cowpox is similar to, but much milder than, the highly contagious and often deadly smallpox disease. Its close resemblance to the mild form of smallpox and the observation that dairy farmers were immune to smallpox inspired the modern smallpox vaccine, created and administered by English physician Edward Jenner.


Characterized by small fluid-containing elevations of the skin (blisters).


The physical act of administering any vaccine.


A branch of medicine that focuses on animal (non-human) care.

Vaccination schedule

A series of vaccinations, including the timing of all doses, which may be either recommended or compulsory, depending on the country of residence.

Viral shedding

Expulsion and release of virus progeny following successful reproduction during a host cell infection. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell. This can also occur in instances of infection caused by some attenuated vaccines. A human with a viral disease can be contagious if they are shedding virus particles, even if they are unaware of doing so.


A substance used to stimulate immunity to a particular infectious disease or pathogen. A suspension of live (usually attenuated) or inactivated microorganisms (e.g., bacteria or viruses), highly defined antigens, or genetic material of the administered to induce immunity and prevent infectious diseases and their sequelae.


The presence of a virus in the blood.

Vaccine Adverse Event Reporting System (VAERS)

A national program managed by the CDC and the US Food and Drug Administration (FDA) to monitor the safety of all vaccines licensed in the United States. VAERS is a system for collecting and reviewing reports of adverse events that occur after vaccination.


The infectious form of a virus as it exists outside the host cell, consisting of a nucleic acid core, a protein coat, and, in some species, an external envelope.

Vaccine Safety Datalink Project (VSD)

A collaboration between CDC and eight large Health Management Organizations (HMOs) to continually evaluate vaccine safety and increase knowledge of vaccine adverse events. Medical records of more than 6 million people are monitored for potential adverse events following vaccination, which supports vaccine safety studies and enables timely investigations.


A virus related to the smallpox and cowpox viruses, which is used in smallpox vaccine.

Vacuum Drying

A drying method that places the object to be dried in an enclosed container to vent air and reduce the pressure with a vacuum pump in order to artificially increase the water vapor partial pressure difference.


Establishing documented evidence that provides a high degree of assurance that a specific process will consistently produce a product meeting its predetermined specifications and quality attributes.


The act or process of making a judgment about the price or value of something.


The expected value of the squared deviation from the mean of a random variable. In other words, a measurement of the spread between numbers in a data set.

Validation Master Plan

A summary outlining the overall plan for validation, including methods, organization, and validation targets, to ensure proper execution of validation.


A subtype of a microorganism that is genetically distinct from a main strain, but not sufficiently different to be termed a distinct strain.

Validation Report

A document describing the reporting format of results after validation.


An acute contagious disease characterized by papular and vesicular lesions. Also known as chickenpox.

Viral vector vaccine

A vaccine that uses a modified, harmless fraction of a different virus (a vector virus) associated with an antigen that can induce production of important instructions that are delivered to the body’s cells.


An acute, highly infectious, often fatal disease caused by a poxvirus and characterized by high fever and aches with subsequent widespread eruption of pimples that blister, produce pus, and form pockmarks. Also known as smallpox.


A vector is any particle used as a vehicle to artificially carry a foreign nucleic sequence (usually DNA) into another cell, where it can be replicated and/or expressed. The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes.