In brief, the article discusses:
- How vaccines work
- How researchers develop a vaccine
- How scientists make sure a vaccine is safe
- A COVID vaccine needs to prevent the disease or reduce its severity by at least 50%
The full article is reproduced below.
How Is A Vaccine Developed?
An immunologist explains the process and offers a timeline to a COVID vaccine.
Even before the novel coronavirus, now known as COVID-19, made its way to the United States, scientists around the world had already begun the race to develop a vaccine. As institutions like the University of Oxford, Pfizer, Moderna, and many more hurdle toward the proverbial finish line, many of us who aren’t scientists may wonder: How do researchers develop a vaccine? And how do we know that one developed so rapidly will be safe?
Where scientists start
Fundamentally, vaccines work by injecting weakened or dead strains of a virus into a person’s body. The presence of these strains stimulates your immune system to produce antibodies, just as it would if you had been exposed to the disease. Think, for example, of chickenpox. Once you get it, you rarely get it again. But with a vaccine, you develop immunity to that disease without having to get sick first.
According to Betty Diamond, MD, an immunologist and the director of Northwell Health’s Institute of Molecular Medicine, scientists’ first task is to find the virus (or bacteria or other germ) that is causing a particular disease and then determine how it works.
Sometimes this process can take years, as scientists try to locate the disease-causing germ; this was the case with HIV. “But we had an advantage with COVID-19,” explains Diamond, “because we had seen other coronaviruses before, including the SARS outbreak in 2003.”
After researchers isolate the germ, they grow it in a culture, so they can find the specific protein that helps the germ bind to the body, as well as the body’s receptor—or doorway.
Because scientists were already familiar with coronaviruses, they knew that the disease entered human cells through a “spike protein.” They also knew that the receptor for this protein within the human body was an enzyme called ACE2, a protein that sits on the surface of many types of cells, including those in our hearts, intestines, lungs, and nasal passages. “So, in this case,” she says, “we were pretty well ahead.”
With this knowledge in hand, researchers can then start the work to develop a vaccine that aims to stimulate the production of antibodies without making a person sick.
Creating and testing a vaccine
While creating vaccines from live or weakened strains works well for diseases that are not potentially fatal or for which there is effective treatment, unfortunately, it’s not an option for COVID. Instead, says Diamond, researchers are focused on using genetic materials such as RNA or DNA to “encode” the spike protein so it can be made by the body safely and stimulate an immune response, rather than introducing the whole virus.
Once scientists have developed a vaccine, they often test it for toxicity on animals first. In the case of COVID, some vaccines were tested in animals, some were not, and others are being tested concurrently with human trials.
Next is a Phase I/ II trial, which is overseen by the Food and Drug Administration (FDA). These are small trials of less than 50 people, in which, Diamond says, “you look for toxicity and a hint of efficacy.”
Once a vaccine has passed this hurdle, researchers move into Phase III human testing, which usually involves a larger sample of 30,000 people or more. In this phase, scientists administer the vaccine to half of the trial participants while giving the other half a placebo. Then, scientists watch to see if participants develop the disease or any side effects and regularly test to determine if any have developed antibodies to the disease.
Because researchers have just begun Phase III trials for a COVID vaccine, they will be watching participants this fall to see how they react—and whether they stay healthy.
What’s the timeline for a vaccine?
That, of course, is what everyone wants to know.
“It’s going to take a while, I think,” says Diamond. “Vaccine development usually takes a long time. People always talk about it being a decade or so, but we really did have the advantage of being able to isolate and grow this virus very quickly.”
Given researchers’ leg up, Diamond thinks that there’s a good chance we’ll have a vaccine in early 2021—especially with so many financial resources behind the effort. But, with so much that still remains uncertain, she says, it’s hard to predict.
Will it be safe?
“I’m less concerned that these vaccines won’t be safe as I am that they won’t necessarily be effective,” says Diamond. “Last year’s flu vaccine was 45% effective. But with a virus as infectious as COVID, that probably won’t be good enough.”
In June, the FDA announced that any COVID vaccine would have to prevent the disease, or reduce its severity, in at least 50% of the people who receive it in order to be approved.
Despite the many challenges, Diamond feels optimistic about the vaccines currently in progress. “I think there’s reason to be hopeful,” she says. “It’s hard to know how effective they’ll be, but the vaccines we’re looking at now are leading to good antibodies, and that’s what you want.”
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