Dr.Abinash Kumar Jha
Vaccine for coronavirus is recently under clinical trials. Researchers around the world are developing more than 165 vaccines against coronavirus and 28 vaccines are in human trials. The first vaccine safety trials in humans started in march but the road ahead remains uncertain. Currently, some vaccines are under phase 3 trials and some are in phase 2 trials. Some trials will fail and others may end without a clear result. But few may succeed in stimulating the immune system to produce effective antibody against the virus.
For the vaccine to get FDA approval to be used by the public the vaccine must undergo several clinical trials and the final results proven to be safe and effective. The phases of clinical trials are:-
1) Pre-clinical trial –Scientists give the vaccine to animals such as mice or monkeys to see if it produces an immune response and to assure whether it is safe for human trials or not.
2) Phase 0 clinical trial –It is the first clinical trial among people. In these trials, a very small dose of a drug is given to about few number of people. They aim to learn how a drug is processed in the body and how it affects the body ( pharmacokinetics and pharmacodynamics).
3) Phase I clinical trial –Done in small group of healthy volunteers. Primary focus of this trial is the determination of clinical tolerance and safety. Once phase I studies have been successfully completed with a satisfactory outcome, the vaccine undergoes phase II clinical trial.
4) Phase II clinical trial –Done in large group of patients to know safety and efficacy of vaccine. The main distinction between phase I and phase II studies is that phase II studies involve larger number of subjects and are often randomised and well controlled. The outcome measures are however often similar.
Phase II vaccine trials are intended to demonstrate the immunogenecity of the relevant active component and the safety profile of candidate in target population. Ultimately, phase II studies should define the optimal dose, initial schedule and safety profile of a candidate vaccine before work can proceed to phase III trials.
5) Phase III clinical trial –It is a large scale clinical trial designed to provide data on vaccine efficacy and safety. These studies are usually performed in large population to evaluate efficacy and safety of formulation of immunologically active component. Vaccine efficacy is the percentage reduction in the incidence rate of disease in vaccinated compared to unvaccinated individuals.
The ultimate acceptance of a prophylactic vaccine as a general public health measure depends upon clear and definitive evidence that the vaccine is safe and actually prevents fromthe infectious disease in question or significantly alters the natural history of disease.
6) Phase IV clinical trials – Done for post marketing surveillance to know rare side effects, chronic side effects, effect of drug on special population – pregnancy, lactation.
Approval – Regulators in each country review the trial results and decide whether to approve or not. During a pandemic, a vaccine may receive emergency use authorization before getting formal approval.
