It’s been four months since researchers in China sequenced the novel coronavirus now known as SARS-CoV-2. In those four months, at least 3.8 million people around the world have been diagnosed with Covid-19, the deadly respiratory disease it causes. As of Friday morning, more than 267,000 people have died. Doctors have been trying lots of existing drugs—from malaria medications to anti-influenza pills to Ebola treatments—in an effort to save patients from the ravages of the disease, which can damage the heart, kidneys, brain, and lungs. But so far, no blockbusters have emerged. Researchers are still testing hundreds of potential candidates in search of a cure.
A vaccine, which would teach people’s immune systems to recognize and fend off the virus before an infection can take hold, would be even better. An inoculated public could get back to work, stop sheltering in place, resume normal life. Developing a safe, effective vaccine against a new pathogen typically takes years, if not decades. That’s because, unlike with experimental treatments, it’s impossible to know right away if a vaccine has worked. During testing, researchers have to wait for participants to encounter the real virus in the wild, which if people are sheltering in place or an outbreak has ended, can take a very long time.
Clinical testing generally has three stages: Phase I involves a few dozen healthy volunteers, Phase II expands to several hundred in an outbreak area, and Phase III repeats the experiment with several thousand. Then US Food and Drug Administration officials must review the data and decide if the shot is safe and effective enough to approve.
But in the face of the current global pandemic, scientists, pharmaceutical companies, and regulators are sprinting at record-shattering speeds to test hundreds of vaccine candidates. Without clinical trial data, it’s impossible to predict which contenders will emerge from the onslaught of experiments as the most successful. For the front-runners, that information could arrive as early as this fall. Here’s what you need to know:
Phase II candidates: Moderna gets the green light, joining Oxford group and CanSino Biologics
On Thursday, Boston biopharma company Moderna announced that its vaccine candidate, mRNA-1273, had been cleared by the FDA to move into a Phase II trial. The study, which will begin enrolling 600 participants in the coming weeks, is designed to begin assessing whether or not the potential vaccine can induce a person’s immune system to produce antibodies that recognize SARS-CoV-2.
With the news, Moderna pulls neck and neck with the current coronavirus vaccine leader: Oxford University’s Jenner Institute. Scientists there had a head start, as The New York Times reported last month. Having already acquired safety data from human trials of similar vaccines for the related coronavirus that causes MERS, Oxford researchers convinced British regulators to push forward with a large Phase II study involving 6,000 people while the outbreak in the UK is still raging. The vaccine is based on a technology that involves genetically modifying a harmless virus to create a SARS-CoV-2 look-alike that doesn’t cause disease but does trigger an immune response.
Moderna’s vaccine candidate, which was developed in collaboration with scientists at the National Institutes of Allergy and Infectious Disease, is made out of messenger RNA, hence the phrase mRNA in the vaccine’s name. This molecule is responsible for carrying the genetic recipes for making different proteins to a cell’s protein production factories. The version inside Moderna’s vaccine carries the instructions for making a little bit of the spike protein that SARS-CoV-2 uses to infect human tissues. The idea is that a vaccine recipient’s cells will produce this partial spike protein, which will train their bodies’ immune systems to recognize the virus and attack it the next time it shows up.