COVID-19 vaccine
COVID-19 vaccine iStock

Drug giant Pfizer and its partner BioNTech have begun an advanced trial of one of their experimental coronavirus vaccines in volunteers in the United States, CNN reported on Tuesday.

The first four participants were dosed Monday at the University of Rochester Medical Center, a spokesman there said. The combined Phase 2/3 trial, which looks for safety, efficacy and optimal dosing of a vaccine or drug, will include up to 30,000 participants.

It was the second advanced trial of a coronavirus vaccine to get under way in the United States Monday. Earlier in the day, Moderna started a Phase 3 trial in the United States of its experimental vaccine.

Pfizer's vaccine is different, noted CNN, but also uses an experimental approach that employs genetic material to stimulate an immune response against a key part of the coronavirus.

Earlier this month, Pfizer and BioNTech released preliminary data showing that one of their vaccines, known only by its experimental name BNT162b1, appeared safe and elicited antibody and T-cell immune responses in a Phase 1/2 trial.

The company, however, has moved ahead with a slightly different candidate. This one will move forward in the combined Phase 2/3 trial, at about 120 sites worldwide, including 39 US states and Argentina, Brazil and Germany.

Pfizer's coronavirus vaccines all use pieces of genetic material to prompt the vaccine recipient to make antibodies against specific parts of the coronavirus. Pfizer and BioNTech's first vaccine targeted a piece of the spike protein, a structure the virus uses to infect human cells. The second vaccine, being moved into advanced trials, targets the entire spike structure.

"This decision reflects our primary goal to bring a well-tolerated, highly effective vaccine to the market as quickly as possible, while we will continue to evaluate our other vaccine candidates as part of a differentiated COVID-19 vaccine portfolio," BioNTech founder Dr. Ugur Sahin said in a statement.

A Phase 1 study typically involves a small number of people and focuses on whether a vaccine is safe and elicits some kind of immune response. In Phase 2, the clinical study is expanded and the vaccine is given to people who have characteristics -- such as age and physical health -- similar to those for whom the new vaccine is intended, according to the US Centers for Disease Control and Prevention. In Phase 3, the vaccine is given to thousands of people and tested for efficacy and again for safety.

Last week the US Department of Health and Human Services and Department of Defense announced a $1.95 billion agreement with Pfizer to produce 100 million doses of a Covid-19 vaccine. The deal also allows the US government to acquire an additional 500 million doses.

On Sunday, White House chief of staff Mark Meadows said that the administration is “hopeful” it can announce new therapies to treat the coronavirus “in the coming days”.

Meadows said in the interview that the White House has been “working around the clock,” with a focus on COVID-19 therapeutics, vaccines and mitigation therapies.

“The president has been very clear — whatever amount of money and whatever amount of time needs to be invested, we’re doing that,” the White House chief of staff said.

Meadows' comments came after President Donald Trump acknowledged last week that the virus will “get worse before it gets better,” following case surges in states such as Florida and Texas.

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