As the number of COVID-19 cases surpasses 3.5 million globally, scientists around the world are scrambling to find a vaccine.
More than 20 candidates are under study, including some that already are being tested in human clinical trials. How soon, then, can we expect an effective vaccine against the novel coronavirus to be available?
Estimates vary from a few months to five years, but the first vaccines may be ready for widespread use in under two years, say Michael J. Buchmeier, PhD, and Donald N. Forthal, MD, scientists with the UC Irvine Center for Virus Research.
“There are more than 60 companies and the NIH [National Institutes of Health] today trying to develop a vaccine,” says Buchmeier, professor of medicine in the infectious diseases division at UCI School of Medicine and a coronavirus expert who has been studying this virus since it was discovered in China in late 2019.
“There is zero chance we will have a vaccine in six months, and I would predict we won’t have a stable situation with a vaccine for five years,” he says, adding that early vaccines will be developed and released, only to be superseded by later products.
How do vaccines work?
Vaccines expose a person to weakened or killed versions of a virus, or to parts of the virus. The immune system sees them as a threat and produces antibodies against them. The memory of that threat remains in the body’s immune cells, so when the virus comes around, they leap into action quickly after being recognized.
Today, only a few vaccines — measles, chickenpox, yellow fever — use an attenuated, or weakened, version of a live virus. These may protect people for 20 or 30 years, or even a lifetime, but there is a small risk that some who are vaccinated will develop the disease.
Others, like some polio and influenza vaccines, use a killed virus. These do not infect people who receive the vaccination.
“We know enough about this virus right now to make a vaccine if only we could get the right formulation,” Buchmeier says. “You should be able to adapt a killed vaccine or a protein encoded by the virus.”
How are vaccines made?
The process to develop a vaccine for a new virus can be long and complicated. But a vaccine that uses an inactivated, or killed, virus can be developed relatively quickly, he says.
The first step is to determine how to develop and deliver a vaccine. Will it be attenuated, killed, or use some other method? Will it be delivered via an injection or nasal spray?
Seed money is needed to develop the proposed vaccine and get clinical research started, which proceeds in multiple phases before the U.S. Food and Drug Administration (FDA) will allow it to be used on the general public.
Clinical trials to determine the safety and efficacy of vaccines proceed in phases. Its safety is first tested in animals. Once proven, testing of its safety can proceed in a small group of humans. If that goes well, a third-phase clinical trial to evaluate its effectiveness as well as safety must be conducted in a larger group of people.
FDA scientists review efforts at every stage and they require researchers to make adjustments and modify clinical trials where necessary.
That’s why the vaccine development process is expected to take up to two years, and ongoing adjustments may mean that control of the virus is not stable for up to five years.
Once a vaccine is on the market, large surveillance studies continue to monitor safety.
Prospects for COVID-19
COVID-19 is caused by a virus formally known as SARS-CoV-2. It’s one of a large group of coronaviruses that cause diseases ranging from the common cold to SARS, short for severe acute respiratory syndrome, and MERS, short for Middle East respiratory syndrome.
Although work began on developing a vaccine for SARS when it appeared on the international scene in the early 2000s, the spread was contained through strict public health measures like those we’re experiencing today with COVID-19. The far more lethal SARS virus resulted in fewer than 8,500 cases and about 900 deaths before it abruptly dissipated.
COVID-19 has proven to be much more contagious than SARS, spreading farther and more quickly. It’s unlikely to disappear soon.
“It would be terrific if [COVID-19] behaved like SARS,” says Forthal, professor of medicine and molecular biology and biochemistry and chief of the Division of Infectious Diseases at UCI School of Medicine. “But I don’t see any reason to suspect that this is going to happen with this virus.
The challenge ahead
One important question is, what’s the future of this epidemic, Forthal says. “Some people predict there will be a seasonality to it, with it returning next fall through winter. What happens if we don’t have a vaccine?”
A person who has survived a COVID-19 infection may have some protection against getting re-infected. Not enough is known yet, but Forthal suspects any protection may be partial, short-lived and result in mild disease in subsequent infections.
“That’s what happens with the common coronaviruses that cause colds,” he explains.
If SARS-CoV2 does reappear before testing is widespread enough to detect hotspots and contain them, and before a treatment or vaccine is developed, Forthal says, “We’ll be right back where we started.”