UPDATE: The U.S. is recommending a “pause” in administration of the single-dose Johnson & Johnson COVID-19 vaccine to investigate reports of potentially dangerous blood clots.
In a joint statement Tuesday, the Centers for Disease Control and Prevention and the Food and Drug Administration said they were investigating unusual clots in six women that occurred 6 to 13 days after vaccination. All six cases were in women between the ages of 18 and 48. More than 6.8 million doses of the J&J vaccine have been administered in the U.S., the vast majority with no or mild side effects. Read more here.
With a third coronavirus vaccine nearing approval in the U.S., what is the difference between the vaccines and should you pick one over the other?
According to medical experts, two vaccines currently available in the U.S., as well as one from Johnson & Johnson, which is currently awaiting emergency use authorization, each offer some level of protection.
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Already, Pfizer and Moderna COVID vaccines have been circulating across the U.S., both requiring two shots for full protection.
But according to an analysis by U.S. regulators released Wednesday, Johnson & Johnson’s single-dose vaccine also offers strong protection against severe COVID-19, setting the stage for a final decision on a new and easier-to-use shot to help tame the pandemic.
The Food and Drug Administration’s scientists confirmed that overall the vaccine is about 66% effective at preventing moderate to severe COVID-19, and about 85% effective against the most serious illness. The agency also said J&J's shot — one that could help speed vaccinations by requiring just one dose instead of two — is safe to use. But that’s just one step in the FDA’s evaluation of a third vaccine option for the U.S.
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The Pfizer and Moderna vaccines now being used in the U.S. and numerous other countries must be kept frozen, while the J&J shot can last three months in the refrigerator, making it easier to handle. AstraZeneca's vaccine, widely used in Europe, Britain and Israel, is made similarly and also requires refrigeration but takes two doses.
J&J tested its single-dose option in 44,000 adults in the U.S., Latin America and South Africa. Different mutated versions of the virus are circulating in different countries, and the FDA analysis cautioned that it's not clear how well the vaccine works against each variant. But J&J previously announced the vaccine worked better in the U.S. -- 72% effective against moderate to severe COVID-19, compared with 66% in Latin America and 57% in South Africa.
Published results from a mass vaccination campaign in Israel showed Pfizer's vaccine was 92% effective at preventing severe disease after two shots and 62% after one. Its estimated effectiveness for preventing death was 72% two to three weeks after the first shot, a rate that may improve as immunity builds over time. Meanwhile, the Moderna vaccine provides a similar level of protection, 94.1%, and requires two shots, 28 days apart. It is not known if either prevents the spread of the virus by people who are asymptomatic.
While the overall effectiveness data may suggest the J&J candidate isn't quite as strong as the two-dose Pfizer and Moderna options, all of the world’s COVID-19 vaccines have been tested differently, making comparisons nearly impossible, CNBC reported.
"If you kind of do a comparison for influenza vaccines, which we do annually, influenza's efficacy can range anywhere from 40% to 60% - and that's a good year," Monica Hendrickson, public health administrator for the Peoria County Health Department said Wednesday. "So again, something that's high public health was, you know, we were hoping for something above 40%. To get to 95%, even 65%, that's a homerun."
Hendrickson noted that the vaccines each hold a high effectiveness against death and severe illness for coronavirus.
"So, really, you're looking at a distinction that from a clinical standpoint, or from, you know, an epidemiological standpoint is very minor compared to what we really are hoping for, which is decreases in death and decreases in severe illness, where they all match up between the three vaccines," Hendrickson said. "Most important thing though is that when these vaccines come on the market, if you have an option to any of these, get one of them."
Hendrickson's message echoes one made by Dr. Marina Del Rios, emergency medicine specialist at the University of Illinois-Chicago, during NBC 5's "Vaccinated State" panel last week.
“Part of my messaging in the community has been that the vaccines on the market are equally efficacious and equally safe," Del Rios said. "The best vaccine you can get is the one that you can get a hold of first, and getting vaccinated earlier, sooner rather than later, protects us from getting sick ourselves and also our community, which has been so terribly devastated by this virus.”
The Pfizer-BioNTech and Moderna vaccines differ from traditional vaccines in their use of mRNA. Instead of introducing a weakened or an inactivated germ into your body, this vaccine injects mRNA, the genetic material that our cells read to make proteins, into your upper arm muscle. It teaches your body how to make the protein that triggers antibody production so if the real virus later enters your body, your immune system will recognize it, according to the federal Centers for Disease Control and Prevention.
Unlike the Pfizer and Moderna shots, the J&J and AstraZeneca vaccines use a cold virus, called an adenovirus, to carry the spike gene into the body. J&J uses a human adenovirus to create its vaccine while AstraZeneca uses a chimpanzee version.
Like Pfizer and Moderna's COVID-19 vaccines, the main side effects of the J&J shot are pain at the injection site and flu-like fever, fatigue and headache. No study participant experienced the severe allergic reaction, called anaphylaxis, that is a rare risk of some other COVID-19 shots, although one experienced a less serious reaction.
The FDA said there were no serious side effects linked to the vaccine so far, although it recommended further monitoring for blood clots. In the study, those were reported in about 15 vaccine recipients and 10 placebo recipients, not enough of a difference to tell if the vaccine played any role.
On Friday, the FDA's independent advisers will debate if the evidence is strong enough to recommend the long-anticipated shot. Armed with that advice, FDA is expected to make a final decision within days.