Phase 3 of vaccine trial

Subject: Science and tech

Context:

University of Oxford and AstraZeneca said they were resuming clinical trials for a new coronavirus vaccine across all U.K. sites.

Concept:

• Vaccine trials follow a four-stage process when they are tested in people.
• After a drug has proven itself safe in a variety of animals — usually mice, rabbits, hamsters and primates that mirror human physiology and the way it reacts to diseases — it enters Phase-1 studies.
• A small group of volunteers is given the drug in small doses and monitored to see if it is safe and whether it was well tolerated. This is also when any occurrences of side effects are closely monitored. On an average, 10-50 candidates are chosen.
• In the normal course, those undergoing the trial must report results to the drug regulator which gives the go-ahead for the next stage of trials.
• Phase-2 is when a group of volunteers, usually in the hundreds, are selected. This is the stage when researchers try to determine what dosage would be necessary for it to take effect or produce the desired response.
• In the case of the COVID-19 vaccine, this is the stage when it’s determined if the inoculation had triggered a desired level of antibodies and a sufficient cell response in terms of stimulating T-cells that are known to block and neutralise the virus particles respectively. Again, side effects and adverse reactions are monitored and reported.
• Each of these stages can take several months and that includes the time taken to recruit patients as well as the time involved in observing the effects of drugs and vaccines at various intervals of time. Such data is again sent to regulators, who, if satisfied, given the green signal for Phase-3.

Phase-3

• In Phase 3 stage, the drug or vaccine is tested at multiple locations in thousands of volunteers or patients.
• In the case of a drug, this is the stage when a new drug is compared to the existing standard of care and when it must prove that it is either more efficacious, or is of similar potency but is safer, better tolerable or delivers any of the goods that the drug makers had claimed when making the drug.
• In the case of a vaccine for a new disease, there is usually nothing to compare it to, so Phase-3 becomes a larger version of the Phase-2 trial. A Phase-3 trial is held at multiple locations to capture the demographic variability in the population.
• It is also double-blinded and randomised and may have multiple treatment arms, meaning some participants may get a placebo, some may get lower doses, some higher doses, and in an ideal trial, neither the doctor nor the recipient knows who is getting the drug and who the placebo.