Does the coronavirus delta variant mean Ill need a vaccine booster?
Both types of vaccine are very effective at preventing severe disease, hospitalizations, and deaths from the virus. Health experts say that is the most important factor. The Johnson & Johnson vaccine is somewhat less effective than the mRNA vaccines at preventing mild and moderate disease  about 66% compared to about 95%. I think in some ways, because of that difference, the [J&J] vaccine has been viewed as an inferior vaccine, when in fact its actually highly effective. And to the extent that a primary objective from a public health perspective is to prevent severe illness, death, hospitalizations, and ICU admissions, its an extremely effective vaccine, said Dr. Esther Chernak, an associate professor at Drexel Universitys Dornsife School of Public Health and College of Medicine, and director of the Center for Public Health Readiness and Communication. However, health experts have been concerned about several variants of the virus that can be more contagious and cause more serious illness. The delta variant  now present in all 50 states  accounts for 26% of new cases in this country. Studies vary, but many suggest that the Pfizer and Moderna vaccines protect people from the delta variant, with slight decreases in effectiveness from the original strain. In May, British researchers reported that the Pfizer vaccine was 88% effective against symptomatic disease from the delta variant. But last week, Israels Ministry of Health announced that its effectiveness was 64% against all coronavirus infections. Another study published last month also found that mRNA vaccines have long-lasting protection. Pfizer said Thursday that its booster study suggests antibody levels increase after a third dose compared to the second dose months earlier. The company said it will ask the Food and Drug Administration for emergency authorization of a third dose in August. There is not a lot of information yet, at least outside laboratory settings, about the effectiveness of the Johnson & Johnson vaccine compared to the mRNA vaccines. A study of the AstraZeneca vaccine, which uses the same technology as the Johnson & Johnson vaccine, was 60% effective against the delta variant. Thats one of the reasons why  in addition to reports of rare blood clots  Canadas vaccine advisory committee supports following a single dose of the AstraZeneca vaccine with a single dose of an mRNA vaccine. But lab studies suggest that people who have received the J&J vaccine are able to neutralize the delta variant, which Chernak said is reassuring. Johnson & Johnson announced earlier this month that its vaccine produced a strong antibody response to the current circulating variants, according to two small, not-yet-peer-reviewed studies. The company said those studies also suggest the vaccine offers immunity for at least eight months. That doesnt mean that it wont last beyond that, it just means that the information still needs to be evaluated on a consistent basis, said Dr. Delana Wardlaw, a family medicine physician at Temple University and a health care advocate. I had the J&J vaccine. Many health experts, including Chernak, say its too early to know. But she said Johnson & Johnsons recent announcement is a positive sign. I think the calls for needing to boost the Johnson & Johnson vaccine  are probably premature. We just dont know that thats necessary. And at least from a laboratory study perspective, theres a lot of indications that it really may not be necessary, Chernak said. Wardlaw agreed. That information did come out too soon, because we did not have enough information to say if the vaccine was or wasnt effective against the variants. And again, we have since received some information that the J&J vaccine is effective against the delta variant, and to date, we do not have any information to say that we have to booster the Johnson & Johnson vaccine, Wardlaw said. There was more data available on the messenger RNA vaccines because those vaccines have been used more than the Johnson & Johnson vaccine. So, of course, that allows for more data to be readily available, she said. If were starting to see increased spikes in cases, if were starting to see decreased response to immunity levels, those are things that will let us know that we will potentially need a booster, Wardlaw added. One of the challenges, Chernak said, is that in the United States more people have received the mRNA vaccines than the Johnson & Johnson vaccine. More than 145 million people in the U.S. have been fully vaccinated with an mRNA vaccine, compared with more than 12 million for the J&J shot. It would be nice to have clinical studies that show the percentage or proportion of people who have breakthrough infections, perhaps relative to other vaccines or just in general. But we dont have a lot of information about that. And its not going to be easy to get that information just given the fact that not that many people have received it from a broader perspective, Chernak said. And unfortunately, what happens when we have surges in particular jurisdictions, particularly fueled by, say, the delta variant, those become opportunities to really look at the effectiveness of different vaccines among folks who have received it in those regions. So well have to see what happens, she said. But I think at the moment, the evidence that all the virus vector vaccines, including the AstraZeneca vaccine, which is not approved in this country, are actually highly effective so far, but specifically with respect to these newer variants, and I think time will tell. And of course, one of the other biggest issues is what variants await us that were not aware of at the moment, that dont exist at the moment, but have the potential to emerge and evade our immune system. Those I think are the biggest concerns.