Two vaccines cleared for emergency use in the United States to prevent COVID-19 appear increasingly likely to work against two highly contagious strains that first emerged in the United Kingdom and South Africa, according to two vaccine experts.
The scientists based their optimism partly on early findings released Friday from an experiment by Pfizer-BioNTech that indicated its vaccine neutralized a key mutation found in both variants. The Food and Drug Administration cleared that vaccine last month and a similar one by Cambridge-based Moderna a week later. Moderna is testing its vaccine against the variants, too.
“That’s great news,” said Dr. Drew Weissman, a professor of medicine at the University of Pennsylvania who helped invent the messenger RNA technology that powers both vaccines. “Before it came out, we were saying we thought the vaccine would be effective. Now we have data that show for the principal mutation, it is effective.”
David Montefiori, a Duke University virologist who is beginning to test the effectiveness of both vaccines against the British strain with help from Weissman, was also encouraged. Nonetheless, he said the Pfizer-BioNTech study was “somewhat limited” because it only focused on one mutation.
The British strain, he explained, has eight mutations on the spike protein — the part of the coronavirus that the pathogen uses to invade a cell — that distinguish it from the dominant virus in the pandemic. The same is true of the South African variant, although some mutations differ between the two.
“The mutation [Pfizer-BioNTech] studied ... is the one scientists were most concerned about because of where it is located on the Spike protein,” Montefiori said in an e-mail. “However, it is important to get a more definitive answer with the complete variant containing all 8 mutations.”
Montefiori and Weissman are studying how effective both vaccines are against the complete British variant, Montefiori said. Researchers at the National Institute for Communicable Diseases in South Africa are doing the same with the strain that emerged in their country, he added. Montefiori hoped results would be released within a couple of weeks.
The Pfizer-BioNTech findings appeared on a pre-print server and have yet to be subjected to peer review. They indicate the key mutation in both strains “does not create resistance” to the immune response stimulated by the Pfizer vaccine, according to a statement by the partnership.
The companies and the University of Texas Medical Branch, which participated in the study, acknowledged more research is needed to determine if the vaccine protects recipients against the two new strains.
Researchers used blood samples taken from 20 people who were vaccinated in Pfizer-BioNTech’s late-stage clinical study, and mixed them with the virus containing the key mutation.
The new coronavirus variants have rattled people around the world.
The website of the Centers for Disease Control and Prevention identifies three coronavirus variations from the dominant strain: one first detected in September and now highly prevalent in London and southeast England; another first detected in October in South Africa; and a third recently isolated in Nigeria.
There is no evidence that the three variants cause more severe illness, according to the CDC, but they have led to tighter restrictions.
Prime Minister Boris Johnson on Monday announced a new national lockdown for England until at least mid-February to combat the new variant. He said people must stay home, as they were ordered to in the first wave of the pandemic in March, because the new strain was spreading in a “frustrating and alarming” way.
The British variant has been detected in parts of the United States, including California, Colorado, Connecticut, Florida, Georgia, and New York. Governor Charlie Baker on Tuesday urged Massachusetts residents to redouble their efforts to control the spread of the coronavirus based on the assumption that the British strain has arrived in Massachusetts, although public health officials have not confirmed that.
The South African strain has not been detected in the United States. But Dr. Scott Gottlieb, the former head of the Food and Drug Administration in the Trump administration, said in an interview on CNBC on Tuesday that it appears to be prevalent in South America and he was worried that it would soon spread in the United States. He also said current medical treatments might not work as well against it, making vaccinations more urgent than ever.
In addition, the White House coronavirus task force sent a report to states on Sunday saying the United States might have its own version of a more transmissible coronavirus that could be fueling the aggressive spread of the virus, CNN reported Friday. But the CDC shot down the report Friday night, saying health officials have not determined that a “USA variant” exists.
The World Health Organization said Tuesday that the strain in the United Kingdom has been detected in a small number of cases in 40 other countries and areas and that the South African variant has been found in six other countries and areas.
The Pfizer-BioNTech and Moderna vaccines were about 95 percent effective at preventing the dominant strain of COVID-19 in large late-stage clinical trials, according to data released by the FDA. Each vaccine requires two shots a few weeks apart.
Weissman, an immunologist with a medical degree and PhD from Boston University whose lab licensed messenger RNA technology used by both vaccines, had already been optimistic that they would prove effective against new variants.
His reason: The coronavirus strain that has locked down much of the world for the past 10 months, he said, is actually a mutation of the original virus first identified in Wuhan, China, last December. The Moderna and Pfizer vaccines were custom-made to prevent the Wuhan strain, he added, but demonstrated even better results against the second coronavirus strain, according to a recently published study he coauthored with Montefiori and other researchers in the journal Cell Host & Microbe.
“I’m pretty confident they will be effective” against the latest variants, Weissman, 61, told the Globe earlier this week. “The spike [protein] is a very big protein, and it has many regions that antibodies can neutralize, so the mutations might affect a few small areas, but they’re not going to change the entire protein to make it resistant.”
The Pfizer and Moderna vaccines rely on synthetic messenger RNA — technology that Weissman has worked on for about 25 years — to instruct cells to build the spike protein after people are vaccinated. When cells make the distinctive protein, it stimulates an immune response that protects people from the virus.
The emergence of new coronavirus strains comes as no surprise to scientists. When a virus replicates itself inside a cell that it has infected, the copies often have small differences because of errors, and those errors can lead to mutant strains. People get influenza shots every year because new variants emerge after such errors.
“The coronavirus replication enzymes are less prone to errors than those of viruses like influenza virus, but still quite prone to errors,” Pfizer said in a statement this week.
Ray Jordan, a Moderna spokesman, said his company is also testing its vaccine against several variants, but he had no details.
Weissman has studied messenger RNA since the 1990s with Katalin Kariko, a colleague at Penn who joined BioNTech, Pfizer’s German partner, in 2013 as senior vice president. After years of trial and error, they figured out a way to create a form of messenger RNA that could sneak its way into cells without being destroyed by the body’s natural defenses.
Derrick Rossi, a stem cell biologist who helped found Moderna in 2010, recently told the Globe that he believes the groundbreaking work of Kariko and Weissman deserves the Nobel Prize in chemistry.
Weissman, whose laboratory has developed a potential COVID-19 vaccine for the government of Thailand, said he would worry about new strains if they proved more deadly. But that hasn’t happened where they have spread.
COVID-19 has caused more than 366,000 deaths in the United States, and the mortality rate is averaging under 2 percent.
“If the mortality rate suddenly increased to 10 percent [as a result of new strains], that’s a big problem,” Weissman said.
Jonathan Saltzman can be reached at email@example.com.