A vaccine reality check
So much hope is riding on a breakthrough, but a vaccine is only the beginning of the end
Nearly five months into the pandemic, all hopes of extinguishing COVID- 19 are riding on a still-hypothetical vaccine. Normal life is on the other side, and we just have to wait— until we have a vaccine.
Feeding these hopes are the Trump administration’s exceedingly rosy projections of a vaccine as early as October, as well as the media’s blow-by-blow coverage of vaccine trials. Each week brings news of “early success,” “promising initial results,” and stocks rising because of “vaccine optimism.” But a COVID- 19 vaccine is unlikely to meet all of these high expectations. The vaccine probably won’t make the disease disappear. It certainly will not immediately return life to normal.
Biologically, a vaccine against the COVID- 19 virus is unlikely to offer complete protection. Logistically, manufacturers will have to make hundreds of millions of doses while relying, perhaps, on technology never before used in vaccines and competing for basic supplies such as glass vials. To complicate it, 20 percent of Americans say they will refuse to get a COVID19 vaccine, and with another 31 percent unsure, reaching herd immunity could be that much more difficult.
The good news is that experts think there will be a COVID- 19 vaccine. Scientists have gone from discovery of the virus to more than 165 candidate vaccines in record time, with 27 vaccines already in human trials. Human trials consist of at least three phases: Phase 1 for safety, Phase 2 for efficacy and dosing, and Phase 3 for efficacy in a huge group of tens of thousands of people. At least six COVID-19 vaccines are in or about to enter Phase 3 trials, which will take several more months.
We are almost five months into the pandemic and probably another five from a safe and effective vaccine — assuming the clinical trials work out perfectly.
All of this means that we may have to endure more months under the threat of the coronavirus than we have already survived. Without the measures that have beat back the virus in much of Europe and Asia, there will continue to be more outbreaks, more school closings, more loneliness, more deaths ahead. A vaccine, when it is available, will mark only the beginning of a long, slow ramp down. And how long that ramp down takes will depend on the efficacy of a vaccine, the success in delivering hundreds of millions of doses, and the willingness of people to get it at all.
“There’s a lot of hope riding on these vaccines,” says Kanta Subbarao, the director of the World Health Organization’s flu collaborating centre in Melbourne, who has also worked on other coronavirus vaccines. “Nobody wants to hear it’s not just right around the corner.”
Vaccines are, in essence, a way to activate the immune system without disease. They can be made with weakened viruses, inactivated viruses, the proteins from a virus, a viral protein grafted onto an innocuous virus, or even just the mRNA that encodes a viral protein. Getting exposed to a vaccine is a bit like having survived the disease once, without the drawbacks. A lot remains unknown about the long- term immune response to COVID- 19, but there are good reasons to believe getting COVID-19 will protect against future infections in some way.
Vaccine-induced immunity tends to be weaker than immunity that arises after an infection. Vaccines are typically given as a shot straight into a muscle. Once your body recognises the foreign invader, it mounts an immune response by producing long- lasting antibodies that circulate in the blood.
But respiratory viruses don’t normally fling themselves into muscle. They infect respiratory systems, after all, and they usually sneak in through the mucous membranes of the nose and throat. Although vaccine shots induce antibodies in the blood, they don’t induce many in the mucous membranes, meaning they’re unlikely to prevent the virus from entering the body. But they could still protect tissues deeper in the body such as the lungs, thus keeping an infection from getting worse. “The primary benefit of vaccination will be to prevent severe disease,” says Subbarao. A COVID19 vaccine is unlikely to achieve what scientists call “sterilising immunity,” which prevents disease altogether.
With this first generation of vaccines, though, speed is of the essence. An initial vaccine might limit COVID-19’s severity without entirely stopping its spread. Think flu shot, rather than polio vaccine.
In recent weeks, multiple vaccine groups have released promising data that show their candidates can induce antibodies that neutralise the coronavirus in lab tests. Their next challenges are about scale: testing the vaccine in a Phase 3 trial with tens of thousands of people to prove it prevents infection in the real world, and then, if it works, manufacturing hundreds of millions, even billions, of doses. This is why even a vaccine that has already been tested in small numbers of people is still many months away.
Vaccine makers need to enroll tens of thousands of people to confirm efficacy and to look for rare and long-term side effects. It will take time to recruit participants, time to wait for them to be naturally exposed to COVID-19, time for any long- term side effects to show up, and time to simply analyse all of the data.
The leading COVID- 19 vaccine candidates rely on technology that ’ s never been used before in approved vaccines. Moderna’s vaccine, for example, is a piece of RNA that encodes a coronavirus protein. Oxford and AstraZeneca’s vaccine attaches a coronavirus protein to a chimpanzee adenov i rus. Neither has been manufactured before on the necessary scale.
Even if all of this goes well— the earliest candidates are effective, the trials conclude quickly, the technology works— another huge task lies ahead: When vaccines are approved, billion doses will not be available at once, and a system is needed to distribute limited supplies to the public.
The virus is already too widespread. A vaccine could still mitigate severe cases; it could make COVID- 19 easier to live with. The virus is likely here to stay, but eventually, the pandemic will end. (Courtesy The
Atlantic)