Coronaviruses have a spike-like structure on their surface called an S protein. The spikes create the corona-like, or crown-like, appearance that gives the viruses their name.The S protein attaches to the surface of human cells.
A vaccine that targets this protein would
prevent it from binding to human cells and stop the virus from reproducing.
Why does it take so long?
First, a vaccine is tested in animals to see if it works and if
it's safe. This testing must follow strict lab guidelines and generally takes
three to six months. The manufacturing of vaccines also must follow quality and
safety practices.
If a vaccine is approved, it will take
time to produce, distribute and administer to the global population. Because
people have no immunity to theCOVID-19 virus, it's
likely that two vaccinations will be needed, three to four weeks apart. People
would likely start to achieve immunity to the COVID-19 virus one to two
weeks after the second vaccination.
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The goal of vaccine developers is to mimic a natural infection as closely as possible without getting a healthy individual sick. There are many ways to do this. You can give a person a weakened virus or a dead virus.
You can also show the
immune system just part of the virus. Many manufacturers are creating vaccines
involving only the “spike protein,” the part on the surface of the coronavirus
that attaches to the human cell it is trying to enter. Once the immune system
has learned what the spike protein looks like, when it encounters it again, as
part of a real coronavirus, it should know how to defend itself.
When vaccine manufacturers talk about “effective,” there are two common definitions. One is preventing people from getting sick. The other is preventing people from getting infected at all. In the case of COVID-19, this could be a nontrivial difference.
The three vaccine candidates:
1- One is being developed by researchers at Oxford University in the U.K. It uses a weakened version of a virus that causes common colds in chimpanzees. Researchers then added proteins, known as antigens, from the novel coronavirus, in the hope that these could prime the human immune system to fight the virus once it encounters it.
2- Another candidate is being developed in China. It uses a killed, and thus safe, version of the novel coronavirus to spur an immune reaction.
3- One U.S. biotech firm, Novavax, is receiving federal funding to produce a vaccine that uses a lab-made protein to inspire an immune response.
About
100 research groups are pursuing vaccines with nearly a dozen in early stages
of human trials or poised to start.
Microsoft
billionaire Bill Gates has committed hundreds of millions of dollars
to develop a vaccine through the Bill and Melinda Gates Foundation.
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Dr. John
Mascola, director of the Vaccine Research Center at the NIH’s National
Institute of Allergy and Infectious Diseases, said he is hopeful because our
natural immune system, when healthy, is capable of handling the infection.
“Most of the time, people recover from COVID-19, because their immune system
eventually clears the virus,” he said. He contrasted the coronavirus to HIV,
for which scientists so far have struggled to create an effective vaccine: “In
HIV, the natural immune system is not effective and people get AIDS.” In this
virus’s case, if we can mimic a natural infection closely enough, it’s likely
that a vaccine will work.
