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Why Emergency COVID Vaccine Approvals Could Pose a Dilemma

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Why Emergency COVID Vaccine Approvals Could Pose a Dilemma

If approval comes before clinical trials end, this could complicate the study of vaccines’ long-term effects


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Scientists say speedy COVID-19 vaccine approvals could damage efforts to study their long-term effects. 

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In the race to inject COVID-19 vaccines into millions of arms worldwide, scientists wrestle with the ethics of whether to allow a clinical trial’s placebo participants to get a vaccine immediately after it’s approved for emergency use. Some say studying the long-term effects of vaccines, such as their safety and efficacy, could be compromised by doing so. Other researchers insist that the potential for human suffering overrides the possibility of long-term data damage.


Emergency-use approvals (EUAs) of COVID-19 vaccines could complicate ongoing clinical trials.

Scientists worry that when tens of millions of people receive COVID-19 vaccines through EUAs, clinical trials will be interrupted or compromised. Positive early results of phase III trials allowed Pfizer, BioNTech and Moderna to seek deployment under FDA’s EUA guidelines in December 2020. Vaccine developers can apply for EUA when half of their trial subjects have taken the full dosage. They must then show limited adverse results and demonstrate effectiveness over two months.

At that point, vaccine suppliers can offer immunization to their placebo groups, even though that would limit important data established by long-term monitoring. Such information includes how long the vaccine’s protection lasts, its long-term safety, and whether it prevents SARS-CoV-2 infections or just protects infected individuals from developing COVID-19.

In 2020, for the first time, the World Health Organization approved emergency use of a vaccine for a poliovirus that was afflicting the Southern Hemisphere, with phase III ...

About the Authors

David Cyranoski reports for Nature from Shanghai, China. Additional reporting by Smriti Mallapaty.

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