(CNN) The first single-dose Covid-19 vaccine has been authorized for use in the United States after advisers to the US Centers for Disease Control and Prevention unanimously voted to recommend the Johnson & Johnson shot for Americans 18 and older.
Distribution of the vaccine began last night, right after the CDC Director Dr. Rochelle Walensky officially rubber-stamped the authorization. The first doses of the vaccine will be delivered as early as tomorrow morning, one senior administration official said in a briefing call.
The J&J vaccine is a bit different than the two already in use in the US. Most importantly, it only requires one dose and is easier to handle, because it can be kept at simple refrigerator temperatures for up to three months. That makes its rollout a lot easier compared to the Moderna and Pfizer vaccines.
The technology is different too. The Moderna and Pfizer vaccines use a brand-new technology called messenger RNA, or mRNA. They deliver genetic material directly into cells, which then follow the genetic instructions to make tiny pieces that look like a part of the coronavirus. Those little proteins stimulate an immune response, generating antibodies and immune cells that "remember" what they look like and that will be ready to respond quickly in case of a fresh attack.
The Johnson & Johnson vaccine uses viral vector technology. A common cold virus called adenovirus 26 is genetically engineered so that it can infect cells, but it won't replicate there. It cannot spread in the body, and won't give people a cold. Like the Pfizer and Moderna vaccines, it delivers genetic instructions.
The J&J vaccine has shown efficacy of 72% in the US and offered 86% protection against severe forms of the disease in the country. Moderna's and Pfizer efficacy rate in clinical trials was 94% to 95%.
Dr. Anthony Fauci, the nation's top infectious disease doctor, urged Americans to take any of the three "highly efficacious" coronavirus vaccines now available to them and not delay by seeking one vaccine over another. "If I were not vaccinated now and I had a choice of getting a J&J vaccine now or waiting for another vaccine, I would take whatever vaccine would be available to me as quickly as possible," he told CNN.
Q: J&J's vaccine has lower efficacy than Moderna and Pfizer. Is it a second-class vaccine?
A: In short: No. Experts agree that all the vaccines provide very good protection by the most important measure, which is whether they keep people from getting seriously ill.
It is true that in trials, the overall global efficacy of the J&J vaccine was 66% against moderate to severe illness and 85% against severe disease. In the US, the vaccine showed efficacy of 72%. Meanwhile, Pfizer and Moderna had efficacy rates of 94% to 95%.
But experts say these numbers can be misleading. The three vaccines have not been compared head to head, so it would be impossible to know if one is better than the other. The trials were different too. Pfizer's vaccine was tested in 43,000 people in the US, Germany, Turkey, South Africa, Brazil and Argentina. Moderna's was tested in 30,000 people, all of them in the US.
Meanwhile, the J&J vaccine was tested in 44,000 people in the US, South Africa and Latin America, and most of the testing was months later in the pandemic than the Pfizer and Moderna vaccines. That meant the vaccine was tested at a time when there were more variants in circulation. Tested in South Africa and in Brazil, an FDA analysis found that the majority of the Covid-19 cases in the J&J trials were due to variants that are thought to be more contagious.
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It's a simple enough concept. People cough, sneeze or simply breathe out particles constantly. If a person is infected with any virus -- including a coronavirus -- viral particles can be carried out on droplets that can become suspended in the air. In a closed room -- such as classroom -- those particles will build up and others will breathe them in.
The solution can also be simple -- air exchange. Swap the particle-laden air for fresh, clean air, and the risk of transmission falls. That's why the CDC posted new recommendations on the importance of good ventilation in preventing coronavirus spread in schools and daycares. Its top recommendation: Open a window.
"I think the narrative about herd immunity keeps cropping up again because it would be nice if Covid-19's gone forever. But, of course, if we can reduce death and suffering by 95%, then that's way more important than herd immunity." -- Dr. Christopher Murray, IHME
What will it take to achieve herd immunity? CNN Chief Medical Correspondent Dr. Sanjay Gupta speaks with Dr. Christopher Murray, who directs the Institute for Health Metrics and Evaluation at the University of Washington, about the role of vaccinations, variants and preventative behavior. Listen now.