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A Covid-19 Vaccine Doesn’t Need to Be Perfect

The first vaccine may not even be 50 percent effective. But that will still help to bring the coronavirus pandemic under control.

A nurse administers a flu shot at a free clinic, wearing protective gear against Covid-19.
Mario Tama/Getty Images
A nurse administers a flu shot at a free clinic. Medical experts are hoping the flu shot this year will help prevent a “twindemic” of both influenza and Covid-19.

This year has brought an unprecedented race to develop, test, and manufacture vaccines and treatments for SARS-CoV-2, the virus that causes Covid-19. Experts say they’ve never seen anything like it: the international collaboration, the round-the-clock work, the scope and scale of more than 150 different vaccines already in the pipeline mere months after the novel virus emerged. And several of those vaccines seem promising. “I feel cautiously optimistic, as a scientist, that we will have a safe and effective vaccine,” Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said last month. “I believe it will happen, and it will happen likely by this end of the calendar year.”

But as vaccines start emerging in the coming months, we may be confronted with a new issue: What if the vaccines are only mediocre? Will we be able to control the virus—and, perhaps more importantly, convince people they should get vaccinated, now and in the future—if the first Covid-19 vaccines are not actually that effective?

The U.S. Food and Drug Administration has set the minimum efficacy of vaccines in these trials at 50 percent, which means the people who receive the vaccines in the trial are half as likely (or less) to get sick as those who receive a placebo. But there’s a chance the efficacy could be lower in reality. After all, what happens in a clinical trial might not mirror what happens in the real world. Some have taken this as evidence that we’re in for a very rough ride, even once vaccines emerge. The release of early, mediocre vaccines could disrupt the clinical trials for better vaccines, as people become less willing to participate in studies if they can get vaccinated at the doctor’s office, a New York Times piece suggested last week. “It has not yet dawned on hardly anybody the amount of complexity and chaos and confusion that will happen in a few short months,” Dr. Gregory Poland, the director of vaccine research at the Mayo Clinic, told the Times.

But even vaccines that only protect a small fraction of the people who get them could make a big difference, experts told me. It just means the vaccines won’t be the only solution. To prepare for what’s ahead, both the public and policymakers should discard the mindset that anything short of a silver bullet is a letdown.


“Vaccines don’t have to be perfect to be potent,” said Dr. Gregg Gonsalves, an assistant professor in epidemiology at Yale School of Medicine. “An imperfect vaccine may be able to stem infections considerably while we wait for the next round of better vaccines to come.” The flu vaccine, for instance, is about 40 to 60 percent effective every year. Even so, it helps keep many people safe from serious illness—and it considerably cuts down on community spread. “We need a vaccine to be able to beat the virus,” he said.

Gonsalves is optimistic when it comes to the development of effective SARS-CoV-2 vaccines, but he cautions that vaccines—even very effective vaccines—don’t halt pandemics right away. “If we have a vaccine in January, first of all, it’s going to take a very, very long time to get people immunized. So we’re not going to have community-wide protection anytime soon,” he said. “I don’t think you’re going to see a vaccine on Tuesday, and on Wednesday, you’re going to see cases collapse.”

It takes time and resources to manufacture vaccines and to set up a system across the country for vaccinating people. Then the immunizations will be given to the people at highest risk of contracting the virus, of becoming very sick, or of spreading it to others. Those who work or live in nursing homes, hospitals, and daycare centers will likely receive the first round of vaccines.

If the first round of vaccines does not work as well as hoped, Gonsalves said, there will be others, particularly given the “global” nature of the current vaccine development efforts. Sometimes, with rarer or more neglected illnesses, approval for the first few vaccines—even if they’re only so-so—means that more won’t be developed, because there’s little market for them. But Gonsalves doubts this would happen with SARS-CoV-2 because of the scale of the pandemic.

Dr. Rajeev Venkayya, president of the global vaccine business unit at Takeda Pharmaceutical Company and a former special assistant for biodefense during the Bush administration, agrees. (Takeda is not developing its own vaccine, but it has agreed to help develop and manufacture the platform vaccine being developed by Novavax.) “There will absolutely be more vaccines coming after the first wave of vaccines are evaluated, even if we have emergency use authorizations granted,” Venkayya told me.

Emergency use authorizations are issued to put a treatment into widespread use before official FDA approval. “If you’re not in a high-risk population, chances are you’re not going to be getting a vaccine under EUA,” Venkayya said. “And since you won’t have access to the vaccine, because you’re not in the EUA population, you have every incentive to be part of a clinical trial, even a placebo-controlled clinical trial, to potentially get access to a vaccine that’s in development.” Until the vaccines have been mass-produced, it won’t be as simple as asking for them at a doctor’s office. It’s possible that companies and researchers could end their trials early, once they have the first indications that the vaccines may work, but they would continue following participants for safety, he added. And a vaccine that emerges in one country won’t necessarily disrupt vaccine development in another, since access to vaccines across borders won’t be immediate or universal.


The first round of vaccines could also be more effective than regulators expected. Vaccine makers and researchers hope for better protection than the 50 percent minimum set by the FDA. “You always try to get a highly efficacious vaccine. Sometimes it’s just not biologically possible to do that, but your goal is to get something that’s as close to 100 percent efficacious as possible,” Venkayya said.

Even if a vaccine offers disappointing coverage, he said, it’s better than nothing. Vaccines will be added to a public health arsenal that includes masks, distancing, ventilation, testing, and other measures. “You can take multiple imperfect interventions, put them together, and collectively create a pretty effective shield against transmission,” Venkayya said, referencing the “Swiss cheese model” of several imperfect layers combining to provide protection. “There’s not a moment in time where you say, OK, we can now stop doing everything that we’ve been doing to prevent transmission. It’ll be a gradual process, as there’s more and more uptake of the vaccine in the population,” he said. “It’s not an all-or-nothing proposition.”

And how well the vaccine works is only one part of the equation, Dr. Ruth Faden, founder of the Johns Hopkins Berman Institute of Bioethics, told me when I asked about President Trump’s efforts to speed up the process before Election Day. “We basically have two challenges toward being able to employ Covid-19 vaccines to help contain this pandemic. One challenge is getting safe and effective vaccines and how quickly we can get them. And the other is getting people to take the vaccine,” she said. Trump’s overt and controversial focus on an October surprise undermines confidence in safe and effective vaccines.

“I don’t want to reinforce the message that we’ll have a perfect vaccine, and that perfect vaccine is going to come in like a knight in shining armor and get us out of this pandemic all on its own. That’s not likely how it’s going to work. But vaccines, good vaccines, safe and effective vaccines, will play a very critical role if we can have them, in helping us to get out of the worst of the pandemic,” Faden said. In order for that to happen, politics need to stay out of the regulatory process—and the public needs total transparency on how the vaccines are being developed and vetted.

Some of the most important parts of the vaccine effort may come down to social science, not medical science—in particular, “incentivizing” people to make good choices, Gonsalves said. “Do we send a mask out to every person in the country? Do we give people tax credits for changing ventilation in their businesses? What kind of things can we do to get people to do the right thing?” he asked. And sometimes it’s about creating the circumstances for people to be able to do the right thing. “If we want people to stay home, maybe we should have universal sick days.”

The pandemic has been a generation-defining event, he said, like World War I or II. “It’s unreasonable to think that we’re going to go back to normal next month, next spring, next fall, whatever. I think the point is that we have a world-historical event, basically—that there was a before and there was an after.”

“We’re going to have to change the way we’ve lived our lives,” Gonsalves said. “Other people have risen to these challenges across human history, and this is our time. So, yes, we’re going to get an imperfect vaccine, and we’re going to still be telling people, you need to wash your hands, you need to wear masks, you need to social distance. We’ll slowly reopen schools and other sorts of places.… Things will be better. But I’m not sure things will be normal.”

Maybe that’s a good thing, he added. After all, this pandemic happened because of the ways our leaders gutted not just epidemic preparedness but also health care and social safety nets. “Even if we could hit the reset button and go to 2019, we’d have avoided this pandemic, but we wouldn’t have avoided the next one,” Gonsalves said. “We have to learn the lessons of Covid-19 so that we don’t have Covid, you know, 2026.”

We have probably all been guilty of thinking in absolutes in the past few months—wishing that 2020 had never happened; dreaming of the day when a vaccine arrives and fixes everything; wondering if the solution is either masks or no masks, lockdowns or no restrictions at all. But it’s never been all or nothing, and there will be no magic cure to take away the hundreds of thousands of people dead and countless others battling chronic illness. We shouldn’t expect a miracle from these vaccines. We also need to rid ourselves of the idea that anything that isn’t a miracle is a failure.