Scientists agree that immunization of placebo recipients with COVID-19 vaccines will affect the study on long-term effects.
The U.S. FDA has approved three vaccines for emergency use after extensive trials. The experimental vaccines are found to be effective and safe in fighting the coronavirus. However, the efficacy studies will continue for at least two years to collect data on the vaccine's effectiveness in real life. It will help in identifying hazards, if any, and demonstrate continued protection.
During the start of the clinical trials, companies had registered volunteers who gave consent to receive shots of an experimental vaccine or a placebo. But as more evidence emerged on the safety of the vaccines, many volunteers opted out of the follow-up research and have been offered vaccine shots through their work or their local health department.
The placebo-controlled trials are considered to be the surest way of obtaining reliable results. Scientists say losing study participants assigned to placebo trials will affect the chances of obtaining reliable evidence. They would no longer be able to compare the health of both groups, and the chances of collecting new data would vanish.