What to Know About Johnson & Johnson’s Single-Dose COVID-19 Vaccine
The CDC now recommends the Pfizer and Moderna COVID-19 vaccines over Johnson & Johnson’s due to rare blood clotting complications.
Johnson & Johnson has been identified as the cause of a new, rare blood condition called TTS, which results in clotting and low platelets.
The vaccine will still be readily available for those who do not wish or who are unable to to access the mRNA vaccines.
Johnson & Johnson’s COVID-19 vaccine is still available—but its use is being narrowed. On December 16, the Centers for Disease Control and Prevention (CDC) updated its vaccine guidance, now recommending that eligible people receive mRNA vaccines Pfizer-BioNTech and Moderna over Johnson & Johnson’s single-dose option.
The decision comes after an influential CDC advisory committee expressed a preference for the mRNA vaccines; since Johnson & Johnson was approved earlier this year, 54 cases of a new, rare condition called thrombosis with thrombocytopenia syndrome (TTS), have been confirmed, a rate of about 3.83 cases per million doses administered. Nine of those patients died. The condition, which causes blood clotting and low platelets, have been confirmed by the CDC. TTS is most common in women between ages 30 and 49, at a rate of about one in 100,000 doses administered, per CDC data.
“Today’s updated recommendation emphasizes CDC’s commitment to provide real-time scientific information to the American public,” CDC director Rochelle Walensky wrote in a statement. “I continue to encourage all Americans to get vaccinated and boosted.”
Supplies of the two-dose Pfizer and Moderna vaccines are high—nearly 100 million doses are available immediately—meaning that there will be no shortage of mRNA options for people getting vaccinated for the first time or rolling up their sleeves for their booster. Johnson & Johnson will remain available for those who do not wish to receive or cannot access the other options. Canada and the United Kingdom have made similar decisions, the CDC says.
This isn’t the first time Johnson & Johnson has faced controversy: Two months after it first reached the arms of people in the United States, the CDC and Food and Drug Administration (FDA) recommended a 10-day pause over blood-clotting concerns.
Now that it’s officially recommended below the other two COVID-19 vaccines, here’s everything experts know about Johnson & Johnson’s vaccine, including how it works, its efficacy, and its side effects—plus how it compares to the other options.
How effective is the Johnson & Johnson COVID-19 vaccine?
Unlike its mRNA cousins from Pfizer-BioNTech and Moderna, Johnson & Johnson’s option uses a modified virus to spur antibody production. This vaccine is about 66% effective at preventing symptomatic COVID-19 and 85% effective at preventing a severe or critical form of COVID-19 that can lead to hospitalization or death at least 28 days after vaccination, according to data released by the company, which was confirmed in an FDA analysis.
The CDC recommends that everyone who received Johnson & Johnson—which, for now, only includes those 18 and older—get a booster shot two months after their shot. Although you can choose any of the three vaccines for your booster, new data shows that mix-and-match vaccinations, or receiving a dose of Pfizer or Moderna instead of a second shot of Johnson & Johnson, leads to the strongest immune response.
All of the available vaccines offer strong, worthwhile protection, as all of them have been shown to protect against severe illness and death, the two worst outcomes, explains Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University. The flu vaccine is usually only up to 60% effective, and that annual shot plays an integral role in decreasing flu-related hospitalizations and deaths every year, he says.
What’s really important with the vaccine is “not how well it protects against symptomatic disease, but how well it protects against severe disease,” says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security. These vaccines have been approved because they’re proven to work; getting vaccinated helps protect you, your loved ones, and those in high-risk groups.
How does the Johnson & Johnson COVID-19 vaccine work?
The Johnson & Johnson vaccine modifies an existing adenovirus, which usually causes colds, with the novel coronavirus’ spike protein, or the piece that latches onto human cells. The resulting adenovirus doesn’t have the ability to reproduce in the human body, meaning it can’t cause COVID-19 or any other illnesses.
When you get the Johnson & Johnson vaccine, the modified adenovirus is pulled inside your cells, where it travels to the cell nucleus, home to its DNA. The adenovirus then puts its DNA into the nucleus, the spike protein gene is read by the cell, and it’s then copied into messenger RNA, or mRNA. Your cells begin making spike proteins, which are then recognized by your immune system, causing your body to produce antibodies to the perceived threat.
It’s like a meet-and-greet between your immune system and COVID-19. Your body now knows how to produce antibodies for the illness, but without having to experience all of the side effects that come with a true SARS-CoV-2 infection. The immune system remembers how to respond to the spike protein, and if you come into contact with it in the future, your body will have the capability to fight it more efficiently. However, it’s not yet clear how long this protection lasts or whether the vaccine prevents person-to-person transmission of the virus, per the FDA.
This technology is unique, but Johnson & Johnson has a lot of experience with it, as it’s already been used for its Ebola vaccine. “They’ve given hundreds of thousands of doses of this similar vaccine,” which has had no major safety issues, says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. Other COVID-19 vaccines, like AstraZeneca’s vaccine, use similar adenovirus technology.
Johnson & Johnson’s vaccine works differently than the mRNA vaccines available from Pfizer and Moderna, which both introduce a piece of genetic code that essentially tricks the body into producing COVID-19 antibodies, no actual virus required. In a way, these vaccines skip some of the steps that adenovirus-vectored vaccines take. Like Johnson & Johnson’s vaccine, Pfizer’s and Moderna’s options are the first of their kind.
Because it requires just one dose and has manageable temperature storage requirements, Johnson & Johnson’s vaccine provided a helpful boost to the U.S. immunization effort when supplies of Pfizer and Moderna were more limited.
What are the side effects of the Johnson & Johnson COVID-19 vaccine?
The vaccine was “generally well-tolerated” in study participants, Johnson & Johnson said in a press release. According to the data so far, the vaccine may cause “mild-to-moderate side effects typically associated with vaccinations,” similar to those expected from the Pfizer and Moderna vaccines. This includes cold-like symptoms, like a headache, body aches, pain at the injection site, and a fever—a normal sign that the body’s immune response is being primed.
TTS, a very rare side effect of the vaccine, is more serious. Again, it’s a condition that causes blood clotting and low plate counts, which could turn deadly; out of 54 confirmed cases, nine of those patients died. TTS is most common in women between 30 and 49 years old; the condition appears in about one in 100,000 women in those age groups who receive Johnson & Johnson, per the CDC.
Because of this rare condition, the CDC now recommends Pfizer and Moderna over Johnson & Johnson. The CDC and the FDA recommend that anyone who received the Johnson & Johnson vaccine monitor for severe headache, abdominal pain, leg pain, and shortness of breath within three weeks of vaccination. If these symptoms develop, contact your healthcare provider for proper diagnosis and treatment.
To be clear, the experts agree that the vaccines are the best way to protect yourself and your loved ones amid a new surge of COVID-19—and this time, both patients and doctors are more aware of the slight risks involved.
This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.
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