Health officials have set targets for how good and how safe a COVID-19 vaccine needs to be, but communicating that to the public can present challenges.
Private David Lewis was hiking with his platoon through the snow, despite feeling unwell from the flu. It was January 1976, and the 19-year-old Lewis was stationed in New Jersey's Fort Dix, where about 230 other soldiers ultimately fell ill. But Lewis, who collapsed 13 miles into the training hike and succumbed soon afterward, was the only one to die. His passing sent the United States into panic mode.
The strain collected at Fort Dix appeared similar to the one behind the 1918 flu pandemic, and this connection made it big news. By the 1970s, high-risk groups were being urged to get flu shots—so the government immediately sought to tailor the vaccine against the Fort Dix strain, hoping 80 percent of the population would take it.
What followed was a debacle. The hastily-developed vaccine was linked to more than 500 cases of paralysis, and 25 people died from it. Soon after news of the Fort Dix outbreak first broke, half of the general public had voiced their intentions to get immunized. But as events unfolded, only 22 percent of the U.S. population ended up getting the vaccine by year's end.
Now, as COVID-19 sweeps across the world and more than 140 vaccines are in the works to protect against it, the question is: How will we know when one is good enough and safe enough to counsel people to take it?
Although a typical vaccine can take years to get off the ground, those designed in this pandemic are moving ahead at a pace never seen before. At least one candidate, from the biotech company Moderna, is headed into phase three trials in July. In May, the U.S. government launched Operation Warp Speed, putting billions of dollars toward accelerating the design and testing of potential vaccines.
Some scientists are wary of settling on the first vaccine that comes to fruition. It's a delicate balancing act for public health officials to decide when a vaccine is ready for mass rollout to the public.
If, for instance, they scale up production of a vaccine with limited effectiveness and promote it heavily, that might dissuade developers from striving to bring a better one to the market. "If you accept a vaccine with low efficacy, then you probably prevent the development of a vaccine with higher efficacy," cautions Roland Sutter, who was coordinator for research, policy, product development, and containment for polio at the World Health Organization (WHO) in Geneva, Switzerland, until retiring in December.
Parsing what makes a COVID-19 vaccine good enough for mass rollout is the primary challenge for scientists and policy makers in the coming months. They'll also need to ensure appropriate safety checks—or risk repeating the mistakes of 1976 and losing public confidence.
SETTING THE GOAL POSTS
Vaccine development comes in stages, starting with phase one trials. These clinical trials generally assess the initial safety of a drug in a relatively small number of people; sometimes about 50 or so participants, although the number can vary widely.
Expanded phase two trials give an inkling of the vaccine's efficacy. That's often gauged by analyzing people's blood to see if antibodies or other immunity sentinels are present that can neutralize the targeted pathogen.
Phase three trials try to better measure how well the vaccine protects people by scaling up to include thousands of participants and typically comparing the protection conferred to those who undergo immunization against those who receive a placebo.
But the real test, vaccine scientists say, comes when these preventative drugs are approved and given widely.
"A clinical trial is still quite a controlled environment," says Charlie Weller, head of the vaccines program at Wellcome, a London-based biomedical research funder. People participating in the testing of a vaccine might be more conscientious about their actions and take fewer risks that might expose them to a virus because they are being followed by doctors. "You know you're in a clinical trial when you're in a clinical trial, and that might change your behavior," she says. "So the real test for a vaccine is when it's rolled out into a population."
Even if they've advanced through these trials, some vaccines are simply more effective than others. (The reasons for this are not always clear. It may have to do with intrinsic factors of the virus being targeted—its propensity to mutate and how it propagates in the body—as well as how our immune system naturally interacts with it.)
