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The Johnson & Johnson COVID-19 vaccine sits on a table at a pop up vaccinations site in the Staten Island borough of New York on April 8, 2021. (AP/Altaffer) The Johnson & Johnson COVID-19 vaccine sits on a table at a pop up vaccinations site in the Staten Island borough of New York on April 8, 2021. (AP/Altaffer)

The Johnson & Johnson COVID-19 vaccine sits on a table at a pop up vaccinations site in the Staten Island borough of New York on April 8, 2021. (AP/Altaffer)

Bill McCarthy
By Bill McCarthy April 13, 2021

If Your Time is short

  • Six women ages 18 to 48 experienced severe adverse reactions involving blood clots within two weeks of getting the Johnson & Johnson COVID-19 vaccine. The FDA and CDC have recommended a pause on the vaccine’s use while they investigate.

  • More than 6.8 million Americans have received the Johnson & Johnson vaccine without reporting similar medical issues. Many millions more have received doses of the Pfizer or Moderna vaccines, which have not triggered any of the same reactions.

  • People who got the Johnson & Johnson vaccine more than a few weeks ago and have not experienced serious blood clotting symptoms should be fine, experts said. Those who got it more recently are also likely to be fine, but they should watch for symptoms.

Question: I got the Johnson & Johnson vaccine. Am I going to be OK?

Answer: People who got the Johnson & Johnson vaccine should seek medical assistance if they experience severe headaches, abdominal pain, leg pain or shortness of breath within three weeks of receiving the shot. Otherwise, there’s little reason for concern about what federal officials said is a very rare reaction involving blood clots.

On April 13, U.S. federal health agencies recommended a pause on the administration of the Johnson & Johnson COVID-19 vaccine while they investigate six reports of a rare but serious type of blood clot among the more than 6.8 million people who got the single-shot vaccine.

Six women who got the vaccine suffered a severe type of blood clot affecting the brain, along with low levels of blood platelets, which help to stop bleeding. All six are between the ages of 18 and 48, and each developed symptoms six to 13 days after vaccination, the Centers for Disease Control and Prevention and the Food and Drug Administration said in a statement.

One woman has died, and another is in critical condition, officials from those agencies said.

The adverse reactions are extremely rare, and the recommendation was made "out of an abundance of caution" while experts work to determine if the vaccine was responsible for the blood clots, officials said. But if you’re one of the millions of people who already received the Johnson & Johnson vaccine, you may be wondering: Am I going to be OK?

For the vast majority of people, the answer is yes.

"For people who got the vaccine more than a month ago, the risk to them is very low at this time," said Dr. Anne Schuchat, the CDC’s principal deputy director. "For people who recently got the vaccines within the last couple weeks, they should be aware to look for any symptoms."

What to watch for if you’ve been vaccinated

The adverse events that led the agencies to recommend pausing use of the Johnson & Johnson vaccine are worth investigating but extremely uncommon, federal officials said.

The six patients experienced blood clots known as cerebral venous sinus thrombosis, combined with low levels of blood platelets.

"This is a really rare event," said Dr. Anthony Fauci, the nation’s top infectious diseases expert, during a White House press conference.

Each of the six cases involved women of childbearing age, but federal officials said it’s too early to say whether preexisting conditions or factors such as oral contraceptive use may predispose certain people to developing blood clots after vaccination.

The CDC and FDA recommended that any person who gets the Johnson & Johnson vaccine should seek medical assistance if they experience severe headaches, abdominal pain, leg pain or shortness of breath within three weeks of receiving the shot.

But for patients who got the Johnson & Johnson vaccine more than a few weeks ago and have not experienced any severe side effects beyond the mild headaches and flu-like symptoms that are common in the first days after vaccination, there’s little reason to stress, experts said.

"If you received J&J more than three weeks ago, there is little to worry about," said Dr. Shruti Gohil, associate medical director for epidemiology and infection prevention at the University of California, Irvine. "If within three weeks, you should know that this event still appears to be rare."

"If nothing has happened within two weeks, you’re good," added Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia. 

Federal officials stressed that vaccines produced by Pfizer-BioNTech and Moderna have not triggered the same problems as the Johnson & Johnson shots, which have accounted for just 5% of all vaccines administered to Americans, according to the White House. The two-dose Pfizer and Moderna vaccines are made using mRNA technology, while the single-dose Johnson & Johnson is not.

"There have been no red flag signals from those, so you’re talking about tens and tens and tens of millions of people who have received vaccines with no adverse effect," Fauci said.

Asked what advice he’d give to people who had recently got the Johnson & Johnson vaccine, Fauci urged people to "pay attention" to severe symptoms such as headaches and seizures.

"Don’t get an anxiety reaction, because remember, it’s less than one in a million," he said, adding that the news "doesn’t mean anything" for people who got the shot months ago.

That rate is about the same or lower than the rate of blood clotting disorders seen in the general population before the vaccines were introduced, Gohil said. But it’s high enough to investigate.

Why are federal agencies recommending a pause for Johnson & Johnson?

After vaccines are made widely available to the public, federal health agencies keep tabs on any adverse medical reactions experienced by patients who get them. 

Recommended pauses at the sign of a potentially serious side effect, such as the blood clots, are "part and parcel of what we expect to have to do as a safety mechanism," Gohil said.

"This pause should actually be very comforting to the public, and affirm that things are being done carefully, responsibly," Gohil said. 

The recommendation is not mandatory, said Dr. Peter Marks of the FDA, who described some scenarios where health care providers could decide to continue administering the vaccine. But a growing list of states and companies such as Walgreens and CVS have decided to halt its use.

Johnson & Johnson said that it has also proactively delayed the rollout of its vaccine in Europe.

The CDC’s Advisory Committee on Immunization Practices, which advises the agency on vaccines, is set to hold a special meeting on April 14 to review the Johnson & Johnson data.

Federal officials described two reasons why the CDC and FDA recommended the pause. The first is to investigate the six cases further, and the second is to advise health care providers on how to assess and treat patients experiencing the same symptoms as the six women identified.

Treating the condition with the common blood thinner Heparin, for example, could accidentally cause "tremendous harm, or the outcome can be fatal," Marks said.

After the CDC and FDA investigate the six cases and any others that arise, the agencies could go in one of several directions, Offit said. They might decide to continue using the vaccine while naming blood clots as a potential side effect, they might scrap its use, or they might limit its use to people who are determined to be at little or no risk of suffering such adverse reactions.

Several European countries restricted the use of another vaccine from AstraZeneca to older adults after reports of similar blood clotting issues. The U.S. has not approved that vaccine.

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Our Sources

U.S. Food and Drug Administration on YouTube, "Joint Media Call: FDA & CDC to Discuss Janssen COVID-19 Vaccine - 4/13/2021," April 13, 2021

The White House on YouTube, "Press Briefing by Press Secretary Jen Psaki, Dr. Anthony Fauci, and Jeff Zients," April 13, 2021

The White House, "Statement from Jeff Zients, White House COVID-19 Response Coordinator on Johnson & Johnson Vaccine," April 13, 2021

U.S. Centers for Disease Control and Prevention, "Joint CDC and FDA Statement on Johnson & Johnson COVID-19 Vaccine," April 13, 2021

Johnson & Johnson, "Johnson & Johnson Statement on COVID-19 Vaccine," April 13, 2021

CNN, "’Don’t freak out’ over Johnson & Johnson vaccine pause, infectious diseases professor says," April 13, 2021

The New York Times, "J&J Vaccine and Blood Clots: A Risk, if It Exists, Is Tiny," April 13, 2021

PolitiFact, "Why Europe took a closer look at AstraZeneca’s COVID-19 vaccine," March 18, 2021

Phone interview with Paul A. Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia and chair of vaccinology at the University of Pennsylvania’s Perelman School of Medicine, April 13, 2021

Email interview with Shruti Gohil, associate medical director for epidemiology and infection prevention, and assistant professor of infectious diseases, at the University of California, Irvine, School of Medicine, April 13, 2021

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