Update, April 26, 2021: On April 23, after 11 days of an FDA- and CDC-recommended pause on the Johnson & Johnson COVID-19 vaccine, the government agencies announced that the benefits of the vaccine outweigh the rare risk of blood clotting. Since the initial pause, there have been 15 reported blood-clot cases out of almost eight million administered vaccine doses; all occurred in women between the ages of 18 and 59 (most were under 50) with symptoms beginning between six and 15 days postvaccination.
Three women have died and seven remained in the hospital as of April 23, according to the Associated Press, and The New York Times reported that 12 of these women developed blood clots in the brain specifically. Symptoms to watch out for include severe headaches, abdominal pain, nausea and vomiting, weakness on one side of the body, difficulties with speech, seizures, and loss of consciousness.
The vaccine label will be updated to indicate the blood-clot risks. A joint statement from the FDA and CDC reads, "teams at FDA and CDC also conducted extensive outreach to providers and clinicians to ensure they were made aware of the potential for these adverse events and could properly manage and recognize these events due to the unique treatment required for these blood clots and low platelets, also known as thrombosis-thrombocytopenia syndrome (TTS)."
Update, April 13, 2021: The FDA and the CDC announced on April 13 that federal distribution and vaccine sites will pause the Johnson & Johnson single-dose COVID-19 vaccine out of an abundance of caution after reports of six blood-clot cases in American women. These women are between 18 and 48 years old, and the cases were reported within six and 13 days of receiving the shot. One woman died and another is in critical condition. Close to seven million doses of the Johnson & Johnson vaccine have been administered so far in the United States, and a joint statement acknowledges that the blood clotting seen in these six cases still appears to be extremely rare.
The type of blood clotting in these cases is cerebral venous sinus thrombosis, meaning, according to the Associated Press, the clots occurred in veins that drain blood from the brain. The clots were also seen in combination with low levels of blood platelets. "Treatment of this specific type of blood clot is different from the treatment that might typically be administered," the joint statement from the CDC and the FDA reads. "Usually, an anticoagulant drug called heparin is used to treat blood clots. In this setting, administration of heparin may be dangerous, and alternative treatments need to be given."
The CDC's Advisory Committee on Immunization Practices will meet on April 14 to review these cases, and the FDA said it will review that analysis and look into these cases as well. The FDA and the CDC advise the same pause on the state level while investigations take place.
Another adenovirus-based vaccine, AstraZeneca, has caused concern in Europe over similar blood-clot reports that may stem from a rare antibody reaction, studies found. Health officials have maintained, despite a pause of AstraZeneca last month, that the benefits of the vaccine far outweigh the risks, and researchers haven't pinpointed any underlying medical condition that might explain the blood clotting, according to The New York Times. The AstraZeneca vaccine has not yet been authorized for emergency use in the US.
Update, Feb. 27, 2021: On Feb. 27, the FDA approved Johnson & Johnson's single-dose coronavirus vaccine for emergency use — it is the third vaccine granted an emergency-use authorization in the US behind mRNA-based shots from Pfizer-BioNTech and Moderna. This authorization allows Johnson & Johnson to distribute its vaccine to people 18 and older.
This adenovirus-based vaccine is 85 percent effective in preventing severe cases of COVID-19. According to the FDA, when a person receives the vaccine, adenovirus type 26 delivers a piece of the DNA that makes the spike protein present in the SARS-CoV-2 virus. Due to this, "the body can temporarily make the spike protein, which does not cause disease, but triggers the immune system to learn to react defensively, producing an immune response against SARS-CoV-2," the FDA stated in a news release.
Johnson & Johnson's vaccine can be stored at normal refrigeration for up to three months. The Moderna and Pfizer vaccines, on the other hand, are stored at below-freezing temperatures (minus four degrees Fahrenheit for Moderna and minus 94 Fahrenheit for Pfizer), making storage and distribution more complex. Johnson & Johnson has pledged to provide the US with 100 million doses by the end of May.
Johnson & Johnson Coronavirus Vaccine Effectiveness
On Feb. 24, 2021, the one-shot Johnson & Johnson coronavirus vaccine was determined to be safe and effective against COVID-19 and prevent hospitalizations and death, according to a review posted by the FDA. According to The Washington Post, the Johnson & Johnson vaccine was 85 percent effective at preventing severe illness, but when moderate cases were factored in, it was only 66 percent effective overall. The New York Times reported that the vaccine was also 64 percent effective overall in South Africa, where most of the cases are from a variant of the virus, which is up seven points from previously released data.
"We know this vaccine prevents 85 percent of the severe disease," said Nancy M. Bennett, a professor of medicine and public health sciences at the University of Rochester School of Medicine and Dentistry, according to The Washington Post. "It was 100 percent effective in preventing hospitalization and deaths, and that's really what's important."
Why Did Johnson & Johnson Originally Pause Its Vaccine Trial?
On Oct. 23, 2020, Johnson & Johnson resumed its large-scale Phase 3 "Ensemble" human trial that began in September and was paused in mid-October. According to The Washington Post, a man who received a vaccination during the trial suffered a stroke that could have been triggered by an infection, but after an investigation, "no clear cause" was identified, and there was no evidence that the vaccine was the cause.
After 11 days of this pause, trial recruitment resumed, "following consultation with the U.S. Food and Drug Administration" and other regulators around the world, Johnson & Johnson said in an Oct. 23 news release.
— Additional reporting by Sam Brodsky
POPSUGAR aims to give you the most accurate and up-to-date information about the coronavirus, but details and recommendations about this pandemic may have changed since publication. For the latest information on COVID-19, please check out resources from the WHO, the CDC, and local public health departments.