Weakened or inactive virus vaccines grown in eggs or cells is what's commonly heard of.
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Now the coronavirus is about to take it to a whole new level in genetically engineered vaccines.
"The mRNA is really a novel strategy," says vaccine researcher, Dr. Eric Daar with Lundquist Institute-Harbor UCLA.
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Instead of injecting bits of the virus, Dr. Darr says Pfizer and Moderna's mRNA approach sends an instruction manual to the cells, telling it to churn out a protein normally found on the coronavirus.
"It's encapsulated in a lipid capsule. It gets injected in your arm," he says, "Then that will get expressed on the surface of the cell and the immune system will respond."
Phase three results look promising and because mRNA are just chemicals, they can be manufactured rapidly.
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The Astrazeneca/Oxford vaccine Dr. Daar is testing uses a viral vector to deliver a small amount of coronavirus' genetic material into the cells. In this case, the vehicle is a cold virus.
"They use the virus to get into the cells, but the virus doesn't replicate beyond that. It can get in once and then that's it," he says.
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The delivery virus can't make you sick, but experts say people might develop an immunity to it, limiting the ability to give multiple booster shots.
Dr. Daar says," The subunit is the other big strategy. That's what people are more familiar with."
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Subunit vaccines use a more traditional method that delivers viral fragments to trigger an immune response.
Novavax is using this type of vaccine. It's slightly slower to produce, but it's a tried-and-tested approach.
Although two vaccines are nearing the finish line, scientists say people can't rest now. Multiple types of vaccines will be needed to meet the global demand to help end this epidemic.
Researchers still need thousands of volunteers to sign up so they can finish their work.
"It's clear that a single vaccine is not going to be enough to interrupt transmission throughout the world. So it's in the interest of all of us to have more than one vaccine," says Dr. Edward Jones-Lopez with the Keck School of Medicine of USC.
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