Medical research (or biomedical research), also known as experimental medicine, encompasses a wide array of research, extending from "basic research" (also called bench science), involving fundamental scientific principles that may relate to a preclinical understanding to clinical research, which involves studies of people who may be subjects in clinical trials.

Both clinical and preclinical research phases exist in the pharmaceutical industry's drug development, where the clinical phase is denoted by the term clinical trial. Though, only part of the clinical or preclinical research is oriented towards a specific pharmaceutical purpose. The basis for fundamental and mechanism-based understanding, diagnostics, medical devices, and non-pharmaceutical therapies means that pharmaceutical research is only a small part of medical research.

A COVID-19 vaccine is intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease (COVID-19). Earlier to the COVID-19 pandemic, work to develop a vaccine against coronavirus diseases like severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS) established knowledge about the structure and function of coronaviruses, this knowledge enabled accelerated development of various vaccines

So many countries have implemented phased distribution plans that prioritize those at highest risk of complications, such as the elderly, and those at high risk of exposure and transmission, such as healthcare workers.