What Is a Placebo Vaccine? Why Is It Used in Covid-19 Clinical Trials?
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Vaccine research began early against the novel coronavirus (SARS-CoV-2) responsible for the Covid-19 Pandemic, which swept the entire world within one year. Now, phase-III clinical trial results are beginning to be announced, and vaccine candidates are being tested in human trials against placebo vaccines as comparators.
What Is a Placebo?
According to the dictionary definition, a placebo is a procedure or drug administered for psychological benefit rather than any physiological effect. It is a substance or treatment involving inert injections, pills or any type of sham treatment designed to have no therapeutic value.
- Related Topic: Placebo and Nocebo – Illuminating Many Mysteries of Medicine through the Power of Expectations
What Is a Placebo Vaccine?
A placebo vaccine is an injection containing no active ingredient. In other words, it is a neutral substance made to look like a vaccine.
What Is a Double-Blind Vaccine Study?
A double-blind study means that neither the participants nor the researchers know whether a person has received the real vaccine or a placebo.
Which volunteer in the sequence will receive the active ingredient is determined in advance using randomization tables. Both the vaccine and placebo are packaged identically, with a code on each package. Healthcare personnel record the code on the substance they administer. Only a few people who plan the study and manage its database know whether this code indicates the active ingredient or placebo. Neither the volunteers nor the healthcare workers who administer the substances and follow them up can know whether a vaccine or an imitation vaccine is being used. Both sides are blind to this fact, which is why it is called double blind as a study design.
In an exceptional situation, for example if a volunteer experiences a serious side effect or death, this code is broken at the study center to determine whether the volunteer received the active ingredient or placebo. In other words, the nature of the substance received by that volunteer is revealed. Otherwise, blinding continues until the study is concluded and analysis begins.
Because obtaining results as quickly as possible was important under pandemic conditions, an interim target was set in Covid-19 vaccine studies for breaking the codes before the study ended. This target was the number of Covid-19 cases seen across the entire study group. This number was again calculated to detect a statistically significant difference between the vaccine and placebo arms.
Why Is a Placebo Used in Vaccine Trials?
A placebo vaccine is the most important guarantee that the results obtained reflect reality rather than chance.
Researchers compare the results obtained from the placebo with those from the real vaccine, revealing how effective the developed vaccine is in protecting against disease. Placebo-controlled experiments are widely regarded as a standard method for testing the effectiveness of new treatments. The purpose of administering a placebo to volunteers is to observe how many people in each group naturally contract the virus and become ill.
In the United States, if the number of volunteers who contract Covid-19 after receiving the real vaccine is 50% lower than the number in the placebo group, the FDA (United States Food and Drug Administration) may grant emergency use authorization. A longer study period is required for the drug regulator to grant permanent approval to vaccine candidates.
Once the clinical trial is completed, if the experimental vaccine is found effective and receives approval for use, those who received the placebo vaccine are among the people prioritized for vaccination.
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