Covid Vaccine: When and How We'll Know It's Safe and Effective

Duane Townsend

The Conversation - September 22, 2020

"I expect that the FDA will approve several vaccines by the end of 2020 under its Emergency Use Authorization authority so that vaccination can begin immediately, starting with high-risk groups including first responders, health care personnel, and the elderly and those with preexisting medical conditions."

With COVID-19 vaccines currently in the final phase of study, you’ve probably been wondering how the FDA will decide if a vaccine is safe and effective.

Based on the status of the Phase 3 trials currently underway, it is unlikely that the results of these trials will be available before November. But it is likely that not just one but several of the competing COVID-19 vaccines will be shown to be safe and effective by the end of 2020.

I am a scientist and infectious diseases specialist at the University of Virginia, where I care for patients with COVID-19 and conduct research on the pandemic. I am also a member of the World Health Organization Expert Group on COVID-19 Vaccine Prioritization.

What is the status of COVID-19 vaccines in human clinical trials?

Phase 3 studies are underway for the Moderna and BioNTech/Pfizer vaccines and the Oxford/AstraZeneca viral vector vaccine.

Each of these vaccines uses the SARS-CoV-2 spike glycoprotein, which the virus uses to infect cells, to trigger the immune system to generate protective antibodies and a cellular immune response to the virus. Protective antibodies act by preventing the spike glycoprotein from attaching the virus to human cells, thereby neutralizing the SARS-CoV-2 virus that causes COVID-19.

In the case of Moderna’s nucleic acid vaccine, the messenger RNA encoding the spike glycoprotein is encased in a fat droplet – called a liposome – to protect the mRNA from degradation and enable it to enter cells. Once these instructions are inside the cells, the mRNA is read by the human cell machinery and made into many spike proteins so that the immune system can respond and begin producing antibodies against this coronavirus.

The Oxford/AstraZeneca uses a different strategy to activate an immune response. Here an adenovirus found in chimpanzees shuttles the instructions for manufacturing the spike glycoprotein into cells.

Phase 1 and 2 studies by pharmaceutical companies Janssen and Merck also use viral vectors similar to the Oxford/AstraZeneca vaccine, while vaccines by Novavax and GSK-Sanofi use the actual spike protein itself.

Animal tests show the vaccines provide protection from coronavirus infection

Studies in animal models of COVID-19 provide convincing evidence that vaccination with the spike glycoprotein will protect from COVID-19. Experiments have show that when the immune system is shown the spike protein – which alone cannot trigger disease – the immune system will generate an antibody response that protects from infection with SARS-CoV-2. ...
Read full report at The Conversation

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