A vaccine is often the solution in Hollywood’s portrayal of contagious disease outbreaks. The fictional vaccine is created on the fly and with little or no testing, is given to the public.
Nothing could be further from reality as vaccine development is a highly regimented process that typically takes 10 to 15 years.
The first step always starts by learning about the germ and how it causes illness. Researchers identify the germ’s weaknesses and develop candidate vaccines to exploit them.
Candidates are then tested in animals in which the germ causes an illness similar to that in humans. It is often challenging to create such animal models but necessary to demonstrate a candidate’s potential effectiveness. Additionally, promising candidates are tested for safety in several different animal species. It usually takes four to six years to get to this point.
The only way to truly know if a candidate is safe and effective is to test it in humans. Human trials can only start if the animal data is convincing of such.
Trials are broken into three phases. During Phase 1, the candidate is given to a small group of adults, usually 20 to 80. They must be extremely healthy to best handle harmful effects if they should occur. Subjects are usually tested in groups with the first group receiving a low dose. If the group does well, the next group is tested at a higher dose and so on until the desired immune response is reached.
The primary aim is testing safety and tolerability but information about the immune response is collected as well. The knowledge gained is used to move into Phase 2.
Phase 2 involves testing the selected dose in several hundred subjects. The subjects’ health is similar to the general population except they must be free of chronic medical conditions. The larger number of subjects allows for discovery of less common side effects.
Phase 2 studies often include other target populations such as the elderly and children. Typically, this phase is designed to show the candidate is protective either by showing it prevents illness or induces protective antibodies levels. Most candidate vaccines fail at this point and do not move into Phase 3.
Thousands of subjects are tested in Phase 3 to identify rare side effects. Usually, subjects are followed for 18 months after vaccination to ensure long-term safety. In total, human testing commonly takes five to 10 years.
So, to answer the million-dollar question: When will we have a COVID-19 vaccine? Fortunately, Phase 1 safety trials are in process, bypassing the initial four to six years of pre-clinical evaluation needed for usual vaccine studies.
This head start is because much is already known from the study of outbreaks caused by other coronaviruses (MERS and SARS). Rapid identification of COVID-19 and sequencing its genetic code were possible because of recent technological advances.
Innovative vaccine types, which can be produced quickly, have been worked on for years. Still, the time required for human testing can only be compressed so much. Optimistic estimates are for a COVID-19 vaccine licensed in 18 months.
While that might not fit the silver screen script, it would be a lifesaving accomplishment.
Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email vaccine.smarts@utmb.edu
by DRS. MEGAN BERMAN AND RICHARD RUPP
Also see:
General Academic Pediatrics at UTMB Health Pediatrics
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