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Vaccines are biological preparations developed from modified versions of the micro-organisms that cause a disease. Vaccines improve or convey immunity to particular diseases, usually in an effort to prevent or cure disease.


Scientific validity refers to how well a measurement, test or study measures what it is intended to measure.

Valstybinė vaistų kontrolės tarnyba


In gene therapy, a vector is a method of delivering DNA into patients' cells. A common vector used in gene therapy is the adenovirus. A gene therapy vector must be customised to attempt treatment of a particular disorder. To be successful, a vector must target the right cells, the gene it is carrying must be activated in the patient, and it must avoid harmful side effects.

Vulnerable participants or populations

Vulnerable participants or populations are individuals or groups of individuals who are unable to give informed consent to take part in a clinical trial, such as children or people affected by mental health conditions, or who may come under pressure from others to take part. It also includes people whose willingness to volunteer in a clinical trial may be unduly influenced by their expectations of taking part.

If a trial is to include people from vulnerable populations, special attention should be paid to protecting their well-being, both by the investigators and the ethics committee that reviews the trial protocol.