Your questions, answered Is there any evidence that mixing the two vaccination types (mRNA and traditional) is more effective than sticking with one approach? My instinct is to select J&J as my booster; I received both Moderna shots last winter. Everything I've seen about mix&match only talks about getting an mRNA after a J&J, but never explores the concept of whether we should ALL be mixing it up. - Anonymous in Idaho I had the same question when health officials started rolling out the booster shots. After getting my two Pfizer doses in the spring, I wondered if my immune system would benefit from a shot of Johnson & Johnson. As you point out, the vaccines use different techniques to toughen your body's defenses. The Moderna and Pfizer shots send in molecules called mRNA to stimulate an immune response that protects you from getting dangerously sick. The Johnson & Johnson vaccine sends a harmless virus called an adenovirus to achieve the same goal. Intuitively, it makes sense that combining the shots in the way you describe might offer a more robust reaction than sticking with what you've got. But there's no indication so far that it does. "We don't have any evidence, especially with the coronavirus, that this actually happens," David Dowdy, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, told me this week. "Whereas we do have evidence — increasing evidence — from people getting boosted with the same shots." The idea that you can get the best of both worlds by combining the vaccines isn't entirely unfounded. There's a "theoretical potential" for using Johnson & Johnson to enhance an mRNA recipient's immune response, according to Robert Atmar, an infectious-disease expert at Baylor College of Medicine and author of a federally-backed study on booster shots. But further research is necessary to see how this works. What is clear is that all three of the vaccines authorized in the United States are safe and effective in any combination. The Centers for Disease Control and Prevention says any booster is fine for those eligible. Data from Atmar's study shows that you'll get the strongest antibody response from three mRNA shots, or boosting a Johnson & Johnson dose with Moderna or Pfizer. But if you want to top your Moderna shots with one of Johnson & Johnson, that's okay, too. If you're confused by all the options, Dowdy recently put together a handy Twitter thread with some recommendations on what to do. But his overarching advice is to keep it in perspective. Again, health officials and experts say any combination will deliver the immune response you need. "After boosters," Dowdy said, "we're talking about a more than 95 percent protection against getting sick." | 
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