Successfully rolling out a coronavirus vaccine by Nov. 1 will rely on clinical trials conducted at unprecedented speed, coupled with public release of research that shows it is both safe and effective, experts say.
Reaction to the Centers for Disease Control and Prevention's letter to states to prepare for "large-scale" distribution of the vaccine in November — specifically, two days before the presidential election — triggered swift concern that political pressure could override commitments to safety.
"I want to see the data," said Dr. Carlos del Rio, executive associate dean of the Emory University School of Medicine in Atlanta. "I need to show that there is true efficacy and safety."
Having a vaccine ready for potential distribution to select groups of high-risk people or front-line health care workers by November will rely on phase 3 clinical trials that started enrolling human volunteers in July.
It's possible that the Data and Safety Monitoring Board, which is run by the National Institutes of Health, could stop the trials early if it's determined that the vaccine works, said Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia. "It's rare, but it does happen," he said.
Doctors will insist on seeing the full data and will demand that the information come from those in the scientific community.
"I want the physician scientists and not the political leadership to make these decisions," said Dr. Steven Nissen, a cardiologist at the Cleveland Clinic.
"If it's made from the Oval Office," Nissen said, "there's going to be a lot of skepticism."
New York Gov. Andrew Cuomo has already said he's suspicious of any vaccine that would be rolled out by early November.
"It's going to be an Election Day miracle drug," Cuomo said during a call with reporters Thursday, adding that the New York State Department of Health would review safety and efficacy data before recommending the vaccine to residents.
The necessary large-scale clinical trials needed to show that a vaccine works are underway, with tens of thousands of volunteers in the United States. Drug manufacturers have committed to produce millions of doses of their vaccines before they even know whether they work.
To show that a vaccine is effective, clinical trials need people who have been infected with the coronavirus. Not thousands of people — just 150.
"When you get that many infections, you will know whether the vaccine works or does not work," Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Disease, told NBC News on Thursday.
Vaccine manufacturers have a goal of enrolling at least 30,000 study participants, some of whom would get the vaccine and others of whom would get a placebo. But it takes only 150 of those people to become infected for researchers to learn whether the shot offers some protection.
"If you have 100 infections in the placebo group and 50 in the vaccinated group, that would suggest that the effectiveness of the vaccine is 50 percent," said Dr. Walter Orenstein, associate director of the Emory Vaccine Center and a professor of infectious diseases at Emory University School of Medicine.
The Food and Drug Administration has said an effective vaccine needs to protect only 50 percent of people to be considered effective.
At least one of the leading vaccine candidates could be on target to have such data before Nov. 1.
On Thursday, Pfizer's chief operating officer, Albert Bourla, said the company could have results from its phase 3 trial as early as next month.
"By the end of October, we should be able to have enough events to say if the product works," Bourla said during a meeting with the International Federation of Pharmaceutical Manufacturers and Associations, a trade group. "Events," in this case, refers to infections.
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Fauci said he "would not be overly surprised" if a vaccine were announced this fall.
"The projection would be that by the end of November or December of this calendar year that we would have an answer whether or not we have a safe and effective vaccine that's approvable," Fauci said.
"Is it possible that it could be before then? The answer is yes. I think it's unlikely, but I think it's possible," he added.
Will the vaccine be safe?
Logging just 150 infections to determine efficacy is unlikely to prove the safety of a vaccine, experts say, which is why continued scientific scrutiny is key. One of the reasons phase 3 clinical trials usually enroll many thousands of people is to tease out those rare adverse events.
"We need to have good, ongoing surveillance to determine whether there are safety problems," Orenstein said. "It's extremely important to have good follow-up."
New vaccines must be rigorously tested to ensure safety. The consequences of not so doing can be devastating: In the 1970s, the U.S. pushed hard for quick work on a flu vaccine, which was later linked to hundreds of cases of Guillain-Barré syndrome, a type of paralysis.
Beyond any evidence of efficacy, trials must answer questions about how a vaccine works in certain populations.
Both the FDA and the CDC have monitoring services to track how people react to vaccines after they've been approved for use.
"It's always a matter of weighing risk versus benefits," Offit said. "There is no such thing as absolute safety when it comes to medicine."