Your questions, answered "Is there any information on how protected a person is against omicron (or delta for that matter) who received the Johnson & Johnson vaccine and the Moderna booster?" — Karen Unfortunately, like so much related to omicron, the data here is quite sparse. The new variant has only been with us for about a month, and the population of people who got this vaccine series is small. According to the CDC, just 2.5 million Americans received a shot of the Johnson & Johnson vaccine followed by a booster dose of the Moderna or Pfizer-BioNTech vaccines, compared with more than 60 million who got three shots of the mRNA vaccines. We know that Johnson & Johnson recipients who got boosted with an mRNA shot are well protected against the delta variant. But omicron is far more slippery. To get a real-world sense of how these patients' immunity holds up against the new variant, "you'd need enough people with that vaccine pattern exposed to omicron... and that's something we just don't have at this point in time," David Dowdy, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, told me. For now, three mRNA shots appears to be the gold standard in keeping people safe from omicron. Health officials say the additional doses of the Moderna and Pfizer vaccines seem to restore most people's antibody levels enough to fight off the variant. A combination of Johnson & Johnson and an mRNA booster doesn't appear to have the same effect, early and not yet peer-reviewed research shows. But that doesn't mean immunity disappears. Many people who got this series are expected to retain significant protection against serious covid-19, according to Jesse Erasmus, a virologist at the University of Washington. "I'd put them in the same category as individuals who had two mRNA vaccines, maybe slightly better," Erasmus told me. "I'd say the majority are going to be protected from severe disease." So far, omicron appears to cause mild or moderate illness in many otherwise healthy people with two vaccine doses, though they may develop more intense and longer-lasting symptoms than fully boosted patients, as my colleague Yasmeen Abutaleb reported this week. An emergency room doctor from Columbia University Medical Center, Craig Spencer, offered similar observations, saying in a widely-circulated Twitter thread that patients he saw with two doses of either the Pfizer or Moderna vaccines had relatively mild symptoms. Patients with a single dose of Johnson & Johnson, without a booster, were worse overall but didn't have life-threatening illness, he said. Erasmus said he hopes officials will soon extend a second mRNA booster shot to Johnson & Johnson patients to bring their protection all the way up to the level we're seeing in people who've gotten a triple dose of the mRNA vaccines. Dowdy, too, said additional boosters for these patients would probably be a good idea at the six-month mark. "I think they should be getting a third dose," Erasmus said. "That's the hard part — waiting for health officials to catch up on the data." For the time being, both experts recommended people in this group take precautions such as masking and distancing. | 
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