Monkeys given the Moderna coronavirus vaccine and then deliberately infected were able to fight off the virus, quickly clearing it from their lungs, researchers reported on Tuesday.
The findings do not guarantee that the vaccine will perform the same way in people, but the results are considered encouraging and a milestone in the struggle against the pandemic. If an experimental vaccine fails in monkeys, that is generally seen as a bad sign for its ability to work in humans. This type of study is considered valuable because infecting people on purpose, though sometimes done, is not standard practice.
On Monday clinics around the country began a Phase 3 trial of the vaccine candidate from Moderna, a biotech company based in Massachusetts, with the aim of enrolling 30,000 people to test for safety and effectiveness.
“The virus was cleared very rapidly in the vaccinated animals,” said Dr. Barney S. Graham, the senior author of a report in The New England Journal of Medicine, and the deputy director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases. Dr. Graham’s scientific team collaborated with Moderna to develop the vaccine.
Unvaccinated animals in the control group did not quickly get rid of the virus.
The vaccine uses a synthetic form of genetic material from the coronavirus, called messenger RNA or mRNA, wrapped in tiny particles of fat that helps it enter human cells. Then, the mRNA prompts the cells to make a fragment of the virus, which primes the immune system to attack if it encounters the real coronavirus.
The study involved 24 Rhesus macaques: eight controls, eight given a low dose of vaccine and eight given a high dose. Each animal received two shots, four weeks apart. A month after the second shot, researchers dripped the coronavirus into their noses, an amount comparable to that found in the airways of infected people. This type of monkey does not become very ill from the coronavirus, but does become infected.
The vaccine did not completely prevent infection, but kept the virus from propagating greatly. The vaccinated animals still had some virus in their noses, but significantly less than unvaccinated animals did.
“If you get a little infection that is cleared rapidly and doesn’t shed very long, it reduces the likelihood of transmission,” Dr. Graham said.
Lab tests also found that the vaccine stimulated strong immune responses, including high levels of antibodies capable of neutralizing the virus — more than found in people who had recovered from the infection.
The lab results were comparable to those seen in people in early tests of the vaccine.
“This bodes well for the Phase 3 trials,” said Dr. Angela Rasmussen, a virologist at Columbia University who was not involved in the study. “It’s still hard to make predictions on what it’s going to do in a huge, diverse group of people, based on monkeys, but it’s reassuring that it provides protection in this model. Overall, my verdict is ‘promising but preliminary.’ ”
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Frequently Asked Questions
Updated July 27, 2020
Should I refinance my mortgage?
- It could be a good idea, because mortgage rates have never been lower. Refinancing requests have pushed mortgage applications to some of the highest levels since 2008, so be prepared to get in line. But defaults are also up, so if you’re thinking about buying a home, be aware that some lenders have tightened their standards.
What is school going to look like in September?
- It is unlikely that many schools will return to a normal schedule this fall, requiring the grind of online learning, makeshift child care and stunted workdays to continue. California’s two largest public school districts — Los Angeles and San Diego — said on July 13, that instruction will be remote-only in the fall, citing concerns that surging coronavirus infections in their areas pose too dire a risk for students and teachers. Together, the two districts enroll some 825,000 students. They are the largest in the country so far to abandon plans for even a partial physical return to classrooms when they reopen in August. For other districts, the solution won’t be an all-or-nothing approach. Many systems, including the nation’s largest, New York City, are devising hybrid plans that involve spending some days in classrooms and other days online. There’s no national policy on this yet, so check with your municipal school system regularly to see what is happening in your community.
Is the coronavirus airborne?
- The coronavirus can stay aloft for hours in tiny droplets in stagnant air, infecting people as they inhale, mounting scientific evidence suggests. This risk is highest in crowded indoor spaces with poor ventilation, and may help explain super-spreading events reported in meatpacking plants, churches and restaurants. It’s unclear how often the virus is spread via these tiny droplets, or aerosols, compared with larger droplets that are expelled when a sick person coughs or sneezes, or transmitted through contact with contaminated surfaces, said Linsey Marr, an aerosol expert at Virginia Tech. Aerosols are released even when a person without symptoms exhales, talks or sings, according to Dr. Marr and more than 200 other experts, who have outlined the evidence in an open letter to the World Health Organization.
What are the symptoms of coronavirus?
Does asymptomatic transmission of Covid-19 happen?
- So far, the evidence seems to show it does. A widely cited paper published in April suggests that people are most infectious about two days before the onset of coronavirus symptoms and estimated that 44 percent of new infections were a result of transmission from people who were not yet showing symptoms. Recently, a top expert at the World Health Organization stated that transmission of the coronavirus by people who did not have symptoms was “very rare,” but she later walked back that statement.
Dr. Rasmussen said that even if a vaccine does not completely prevent infection, but makes the illness less severe and cuts the risk of death, it is still a valuable public health measure.
Another outside expert, Dr. Paul Offit, an infectious disease expert at the University of Pennsylvania and Children’s Hospital of Philadelphia, said: “It’s always encouraging when things work in nonhuman primates, but nonhuman primates aren’t humans. We really only learn about these products when they’re put in humans.”
Dr. Graham said, “I think we have a chance of having some protection from this vaccine, but we have to do the Phase 3 trial to find out.”
He said the study could also help establish guidelines for evaluating this type of research on other vaccines.
“It kind of puts a stake in the ground for what kind of things might be needed to see this level of protection in a nonhuman primate,” Dr. Graham said. “We don’t know how it will relate to Phase 3. We’ll find out as data builds from this product and others. We’ll develop a more clear picture of which vaccines work and maybe why they work. But we really need the human data.”
