Early studies show the coronavirus variant that’s spreading widely across California is somewhat resistant to antibodies that fight off infection, but the vaccines still should offer plenty of protection, infectious disease experts say.
Antibodies generated by the vaccines, or by previous coronavirus infection, were two to four times stronger against earlier versions of the virus compared to the new variant, scientists at UCSF found in laboratory studies. They released preliminary results this week.
The finding is disappointing, but not cause for alarm, said scientists involved with the study as well as outside observers. The vaccines are extremely powerful, and even with a drop in antibody strength, they likely will be about as effective against the variant as they are against the original version of the virus they were designed to fight.
If there is a reduction in effectiveness, the vaccines still should prevent almost all cases of severe illness and death, even from the new variant.
“In my opinion it will make no difference in terms of the efficacy of the vaccine,” said Raul Andino, a UCSF virologist who led the variant antibody research. “I would say there is nothing to be afraid of just now.”
The California variant is now dominant in much of the state; there are technically two variants, known as B.1.429 and B.1.427, but they are nearly identical and carry the same key mutations. Scientists generally are studying them as a singular variant.
Two teams of UCSF scientists released study results this week showing for the first time that the variant appears to be more infectious than earlier coronavirus versions, and that it may also cause more serious illness and be resistant to antibodies.
All of the results suggest this variant is worrisome and should be closely monitored. That it’s so widespread should remind people to stay vigilant about wearing masks and keeping social distance, even as the winter surge fades and the state reopens, experts warn.
But the antibody research in particular is important to put in context, scientists say. The research itself is critical: If variants appear able to evade vaccines, public health officials want to know that right away. The vaccine manufacturers, too, need to know if they should update their formulas to better match new variants.
The California variant — along with one from South Africa — could render the vaccines marginally less effective in subtle but important ways. As with so many aspects of this pandemic, scientists won’t have all those answers until they’ve done more research.
Studies in South Africa have shown that vaccines work somewhat less well against a different variant there. The Johnson & Johnson vaccine, for example — which the Food and Drug Administration is considering for emergency authorization — is about 64% effective in South Africa and 72% effective in the United States. Moderna updated its vaccine to better match the South Africa variant after studies found it was less effective; the new version is still under review.
Similar studies haven’t been done yet for the California variant. For now the only sign that there may be trouble is antibody resistance in the lab, but that doesn’t mean the vaccines won’t work in real life.
Antibodies are the immune system’s most powerful response to disease-causing pathogens. They are specialized proteins let loose by the immune system to target and kill invaders.
When someone is infected with a virus or other pathogen, the immune system learns from that experience and if it encounters the same virus again, it will quickly gather an army of antibodies. Vaccines similarly prime the immune system to release antibodies. The vaccines used in the United States trigger huge antibody responses that are about 95% effective at killing the coronavirus.
To understand antibody effectiveness against the new variant, UCSF scientists did a common experiment called a neutralization assay. They collected antibodies from people who had been infected and others who had been vaccinated, and diluted those antibodies to varying degrees.
They let samples of the California variant and a non-variant virus soak in the various antibody dilutions for half an hour. Then the antibody-soaked viruses were mixed with cells in petri dishes to test whether the viruses were still alive and infectious. Scientists focused on how much the antibodies could be diluted and still manage to kill, or neutralize, the virus.
The UCSF team found that antibodies generated by the vaccines could be diluted twice as much against the original virus as they could against the California variant. Antibodies from people who were previously infected could be diluted four times as much.
In other words, the antibodies were stronger against earlier versions of the virus compared to the new variant. Similar studies from South Africa found antibodies to be six to 10 times stronger against the original form of the virus compared to the variant there.
The California variant should cause concern, “but certainly not like South Africa,” said Dr. Jay Levy, an infectious disease expert at UCSF who said he found the results released this week reassuring. “The vaccines will work, unless it mutates to become worse. You’re still neutralizing the virus.”
There are several caveats to these early results, the most important of which is these are laboratory experiments that analyze interactions between the virus and antibodies in a highly controlled setting. In real life, the body mounts a complex immune response to the virus. That may be further helped or hindered by environmental factors that can’t be replicated in a lab.
Vaccine effectiveness is nuanced too. The vaccines in use in the United States are nearly 100% effective at preventing hospitalization and death from COVID-19, but it’s unclear how well they protect against asymptomatic disease. Vaccinated people may still be carriers of the virus. It’s also not yet known how long vaccine protection lasts.
The key takeaway remains: Everyone should get vaccinated when their turn comes, said Bali Pulendran, a professor of microbiology and immunology at Stanford.
“If you asked me, ‘would you take the vaccine in the hope that it might offer some protection against variants?’” he said. “My answer would be a resounding yes.”
Erin Allday is a San Francisco Chronicle staff writer. Email: eallday@sfchronicle.com Twitter: @erinallday
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