What you need to know about the J&J vaccine pause

  • The U.S. is recommending a "pause" in use of the single-dose Johnson & Johnson COVID-19 vaccine, which also is known as the Janssen vaccine.

    The U.S. is recommending a "pause" in use of the single-dose Johnson & Johnson COVID-19 vaccine, which also is known as the Janssen vaccine. Associated Press

Updated 4/13/2021 9:04 PM

Federal health officials Tuesday called for a pause in the use of the Johnson & Johnson single-dose COVID-19 vaccine after reporting six women 18 to 48 years old had developed rare and severe intracranial blood clots.

One woman died. Three remain hospitalized, authorities said.


Nearly 7 million doses of the vaccine have been administered in the U.S., much fewer than the vaccines from the other two manufacturers, Pfizer-BioNTech and Moderna.

Here are some answers to frequently asked questions about this "pause" in the use of the Johnson & Johnson vaccine from medical professionals and other health experts.

Q. Is there any significance that it's happening only in women?

A. Premenopausal women are more susceptible to blood clots, said Dr. Emily Landon, head of the University of Chicago's infectious disease prevention and control program. Women on hormonal birth control are at an increased risk of blood clots in general.

"There's a relationship between estrogen and blood clots, so there's a biologically plausible reason for this connection," she said.

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"The fact that they can narrow the risk down to a gender and age group means that it will drag on a little, but for those individuals who won't be able to receive this vaccine type. But one of the first things that will be done is determining who definitely is not at risk."

Q. What are the symptoms?

A. Anyone who received a dose of the Johnson & Johnson vaccine "who develop severe headache, abdominal pain, leg pain or shortness of breath within three weeks after vaccination should contact their health care provider," according to a news release issued Tuesday by the U.S. Centers for Disease Control and Prevention.

The statement also notes the women who developed the blood clots had symptoms six to 13 days after inoculation.

Q. Is a bad headache the day after a Johnson & Johnson vaccination a sign of serious side effects?

A. Serious blood clot problems "are different than the short-term reactions that we will see in people in the 24 to 48 hours right after they get vaccinated," Chicago Department of Public Health Commissioner Allison Arwady said Tuesday. "If people had a headache in the day right after they got vaccinated and it went away, I would not have significant concerns about that at all."


Q. Why aren't they pausing the other two vaccines?

A. The vaccines are different types.

The Johnson & Johnson vaccine uses a different method to instruct human cells to fight the virus than the other vaccines use. The Johnson & Johnson vaccine is an inert adenovirus, some of which are often responsible for the common cold, that is specially engineered to carry the COVID-19 protein code that triggers our immune systems.

The Pfizer-BioNTech and Moderna vaccines use messenger RNA to deliver a "recipe" to human cells to recognize the viral invader and make the antibodies to fight it, Landon explained.

Q. How dangerous is the Johnson & Johnson vaccine?

A. The CDC and FDA took the rare step of pausing use of a vaccine to ensure its safety to the public. There is no timeline for when it will be reintroduced.

"But this is what should give us more trust," Landon said. "It was wise for us to pause and take a look at it. However, this is an event that's literally less than one in a million, something that happens less than getting struck by lightning. That's the level of safety you're being protected with. The risk of dying from COVID is much greater than one in a million."

• Daily Herald staff writer Marni Pyke contributed to this report.

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