The main concern about B.1.1.7 is that it is highly infectious and spreads quickly among the unvaccinated, potentially overwhelming hospitals in areas where cases are surging.
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Do the vaccines work against B.1.1.7?
All of the major vaccines in use — Pfizer-BioNTech, Moderna, Johnson & Johnson, AstraZeneca, Sputnik and Novavax — have been shown to be effective against B.1.1.7. We know this from a variety of studies and indicators. First, scientists have used the blood of vaccinated patients to study how well vaccine antibodies bind to a variant in a test tube. The vaccines have all performed relatively well against B.1.1.7. There’s also clinical trial data, particularly from Johnson & Johnson and AstraZeneca (which is the most widely used vaccine around the world), that shows they are highly effective against both preventing infection and serious illness in areas where B.1.1.7 is circulating. And in Israel, for instance, where 80 percent of the eligible population is vaccinated (all with the Pfizer shot), case counts are plummeting, even as schools, restaurants and workplaces open up, suggesting that vaccines are tamping down new infections, including those caused by variants.
If the vaccines are working, why do I keep hearing about “breakthrough” cases?
No vaccine is foolproof, and even though the Covid vaccines are highly protective, sometimes vaccinated people still get infected. But breakthrough cases of vaccinated people are very rare, even as variants are fueling a surge in case counts. And the vaccines clearly prevent severe illness and hospitalization in the few vaccinated patients who do get infected.
So what’s the risk of getting infected after vaccination? Nobody knows for sure, but we have some clues. During the Moderna trial, for instance, only 11 patients out of 15,210 who were vaccinated got infected. Both Pfizer and Moderna now are doing more detailed studies of breakthrough cases among vaccinated trial participants, and should be releasing that data soon.
Two real-world studies of vaccinated health care workers, who have a much higher risk of virus exposure than the rest of us, offer hopeful signs. One study found that just four out of 8,121 fully vaccinated employees at the University of Texas Southwestern Medical Center in Dallas became infected. The other found that only seven out of 14,990 workers at UC San Diego Health and the David Geffen School of Medicine at the University of California, Los Angeles, tested positive two or more weeks after receiving a second dose of either the Pfizer-BioNTech or Moderna vaccines. Both reports were published in the New England Journal of Medicine, and are a sign that even as cases were surging in the United States, breakthrough cases were uncommon, even among individuals who were often exposed to sick patients. Most important, patients who were infected after vaccination had mild symptoms. Some people had no symptoms at all, and were discovered only through testing in studies or as part of their unrelated medical care.
Researchers are still studying whether the variants eventually might increase the number of breakthrough cases or if vaccine antibodies begin to wane over time. So far, data from Moderna show the vaccine still remains 90 percent effective after at least six months. Pfizer has reported similar results.
A recent study of 149 people in Israel who became infected after vaccination with the Pfizer vaccine suggested that a variant first identified in South Africa was more likely to cause breakthrough infections. However, those eight infections occurred between days seven and 13 following the second dose. “We didn’t see any South Africa variant 14 days after the second dose,” said Adi Stern, the study’s senior author, a professor at the Shmunis School of Biomedicine and Cancer Research, Tel Aviv University. “It was a small sample size, but it’s very possible that two weeks after the second dose, maybe the protection level goes up and that blocks the South Africa variant completely. It gives us more room for optimism.”