Covid-19: What is a placebo? Why is it used in vaccine trials?
After Haryana health minister Anil Vij, who had participated in a vaccine trial, tested positive for the coronavirus disease (Covid-19), it triggered a lot of questions around the efficacy of the vaccine candidate Covaxin, developed by Bharat Biotech. The company later issued a clarification, saying the trial volunteers receive the two vaccine doses 28 days apart and the efficacy of the vaccine can be determined 14 days after the second dose is administered.
The Biotech firm further added that the phase 3 trial is a double-blinded study where half of the participants receive the vaccine and the other half receive a placebo. A double-blinded study means neither the participant nor the investigator knows whether the person was administered a vaccine or a placebo.
What is a placebo?
According to the dictionary definition, a placebo is a medicine or procedure prescribed for the psychological benefit to the patient rather than for any physiological effect. It is a substance or treatment which is designed to have no therapeutic value, including inert injections, pills, or any other kind of fake treatment.
Why is it used in vaccine trials?
The researchers compare the results of the vaccine with those obtained from the placebo and the placebo-controlled trials are widely regarded as a standard method for testing the efficacy of new treatments. The aim of administering a placebo in trial volunteers is to observe how many people in each group naturally contract the virus and fall ill.
In the United States, if the number of inoculated volunteers contracting Covid-19 is at least 50 per cent lower than the number in the placebo group, Food and Drug Administration (FDA) can grant the emergency use authorisation. The drug regulator requires a longer period of study to grant permanent approval to the vaccine candidates.
The United Kingdom has authorised Pfizer’s vaccine for emergency use and the company is now awaiting emergency use authorisation from the FDA for its roll-out in the US. The biotech firm had announced that the final efficacy analysis of its vaccine candidate, BNT162b2, undergoing Phase 3 trial met all of the study’s primary efficacy endpoints.