Did you get a Johnson & Johnson vaccine? Here's what you need to know

If you received the Johnson & Johnson vaccine less than three weeks ago, here are symptoms you should be watching for, although serious side effects have been very rare.

  • Severe headache
  • Abdominal pain
  • Leg pain
  • Shortness of breath

The U.S. Food and Drug Administration and the Centers for Disease Control and Prevention are reviewing data involving the single-dose COVID-19 vaccine made by Johnson & Johnson and six cases of a rare and severe blood clot that affected women between the ages of 18 and 48.

The women's symptoms occurred between six and 13 days after the shot. One died and one is in critical condition, federal officials said Tuesday morning.

The six women had a blood clot called cerebral venous sinus thrombosis (CVST) in combination with low levels of blood platelets (thrombocytopenia).

Blood clots and low platelet counts have not been found to be an issue with the Pfizer and Moderna vaccines, which use a different type of vaccine technology, called mRNA. The vast majority of vaccinated Americans have received the Pfizer or Moderna vaccine. 

Estimated risk of blood clot is low

The Johnson & Johnson vaccine is still less risky than getting COVID-19, some health experts emphasized Tuesday after the two federal agencies recommended the vaccine's administration be paused pending a safety review.

"I don't think if you've gotten a J&J vaccine you should be particularly worried," Tara Kirk Sell, a senior scholar at the Johns Hopkins Center for Health Security,told The Arizona Republic.

"It's good that the FDA and CDC are taking a close look at this, and it's good that there is transparency with adverse events. But if we compare it with the risks of getting COVID-19 and having a severe outcome from that, I think the risk balance is still going to be in favor of getting the vaccine."

Nearly 7 million doses of the Johnson & Johnson COVID-19 vaccine have been administered in the U.S., including 122,000 in Arizona. Arizona's top health official said Friday she was following news out of other states but was not aware of any adverse events from the J&J vaccine in Arizona.

Sell said, "It's also going to require people to have nuanced thinking about risk. Right now it doesn't look like a severe risk, but if there are headlines blasted across the country about blood clots, people start to have a disproportionate view of the risk."

Dr. Deepta Bhattacharya, associate professor of immunobiology at the University of Arizona, said in a statement released by the Pima County Health Department that the estimated risk of a blood clot from the J&J vaccine is about 1 in a million, which is a far lower risk than an unvaccinated person has of dying from COVID-19 if they become infected.

“Let’s say that there is a 10% chance that someone will catch COVID-19,” Bhattacharya said. “Then the overall risk for an unvaccinated person catching and dying from COVID-19 is about 1 in 1,000, which is about 1,000 times more likely than having a complication from the J&J vaccine.”

The blood clot risk for the J&J vaccine is very low but could be slightly higher than 1 in 1 million, Sell said. She noted that the blood clots seem to be associated with younger, working-age women, so the risk to certain women could be higher, but more data is needed.

FDA and CDC officials in a Tuesday morning news briefing did not draw conclusions about any sub-populations that could be more at risk given the small number of known cases. They said they may learn of more cases since announcing the pause and spreading information about the blood clots.

“A review of six is difficult to make generalizations from," CDC Principal Deputy Director Dr. Anne Schuchat said. "We’re going to have our expert committee take a careful look and we’re of course trying to ensure that providers will report suspect episodes so that they can be further investigated because the numbers are quite small — small enough that it’s hard to generalize, but large enough that we wanted to take the action with the pause.”

Health care providers have to report adverse events related to the COVID-19 vaccine to the Vaccine Adverse Event Reporting System. The CDC also has a "V-safe After Vaccination Health Checker" smartphone-based surveillance tool for people who have received a COVID-19 vaccine to report any side effects directly to the federal agency.

'We are committed to safety and transparency'

Numerous people took to Twitter Tuesday to share the odds of women getting blood clots from hormonal birth control pills. It's about 1 in 1,000, a far higher identified risk than the current known risk of getting a severe blood clot from the Johnson & Johnson vaccine.

But the difference with the blood clots associated with the Johnson & Johnson vaccine is that they are severe, rare and could worsen if treated with heparin, which is typically used to treat blood clots. Alternative treatments are needed, federal officials said, which is why messaging is important.

Public health experts worry the news about Johnson & Johnson will affect vaccine confidence at a time when it's important for a majority of the population to be immunized to prevent future COVID-19 outbreaks.

"The overall concern for what this does to vaccine hesitancy is almost a larger problem," Sell said. "This just shows us that we have these symptoms in place to identify when these rare events occur and to say, 'Wait, we're going to figure out what is going on.' I think people should feel comforted and confident about those systems."

FDA and CDC officials said at the news briefing that's part of why they recommended the pause, which they hope to resolve quickly and see as part of their commitment to transparency and safety in the COVID-19 vaccine rollout.

“Right now I’d like to stress that these events appear to be extremely rare. However, COVID-19 vaccine safety is a top priority for the federal government, and we take all reports of adverse events following vaccination very seriously,” acting FDA Commissioner Dr. Janet Woodcock said.

Asked whether pausing the rollout was an overreaction given six adverse outcomes in nearly 7 million shots, Schuchat from the CDC said sharing information and reviewing the data is necessary. 

“We are committed to safety and transparency and to expeditiously learning as much as we can so that further steps can be taken. When we saw this pattern and were aware that treatment needed to be individualized for this condition, it was of the utmost importance for us to get the word out," she said.

"That said, the pandemic is quite severe, and cases are increasing in a lot of places and vaccination is critical, so we want to make sure that we make some recommendations quickly.”

The CDC's immunization committee is expected to meet Wednesday to review the cases, and the FDA also will investigate. 

Pharmacist Jay Mitchell administers the Johnson & Johnson COVID-19 vaccine to Hector Felix at the South Mountain Community College in Phoenix on April 10, 2021.

What patients should know

Although severe outcomes with the J&J vaccine have been very rare so far, CDC and FDA officials want patients and health care providers to keep an eye out.

The FDA is revising its fact sheet for health care providers administering the vaccine and for recipients and caregivers to include information on the adverse events and to make sure providers and patients weigh risks and benefits, Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said during the briefing.

For patients who have recently gotten the J&J vaccine, there are signs they can look out for.

“I know that the information we’re providing today is going to be very concerning to Americans who have already received the Johnson & Johnson or Janssen vaccine, and I want to let you know what we’re doing to learn more and to protect people in the meantime, and what you can do to be on the alert,” Schuchat said.

For people who got the vaccine more than a month ago, the risk is very low at this time, Schuchat said. People who got the vaccine within the past couple of weeks should know to watch for symptoms like severe headaches, abdominal pain, leg pain or shortness of breath and should contact their doctor and get medical care if that happens, federal officials said.

Those symptoms are different from the flu-like side effects, which can include headaches and muscle pain, that are typical in the couple of days immediately after the vaccine.

In clinical trials, side effects from the J&J COVID-19 vaccine were common within seven days of getting vaccinated but were mostly mild to moderate. Side effects were more common in people 18 to 59 years old compared with people 60 years and older, the CDC says.

Those six cases of concerning blood clots happened typically about a week after vaccination and no longer than three weeks after vaccination, with a median of about nine days after, Marks said.

FDA and CDC officials said there are too few cases right now to get a sense of whether certain people may be more predisposed to a severe reaction from the vaccine. More information may be available after Wednesday’s meeting of the Advisory Committee on Immunization Practices to review the data.

While the federal recommendation is to pause using that vaccine for now, it's not a mandate to stop using it, so patients and health care providers can still decide to use the J&J vaccine if they feel it's appropriate, Marks said. 

What health care providers need to know

Part of the pause that federal officials are recommending is to give health care providers time to understand what’s going on and how to respond in a rare case that a patient may be having a reaction to the J&J vaccine.

Federal officials want to make sure the health care system knows how to diagnose, treat and report these rare but severe events.

If health care providers see people presenting with a low blood platelet count or blood clots, they should ask about their recent vaccination history to determine the best treatment plan.

Marks said CVST tends to occur in between two and 14 people per million with normal platelet counts per year, but the six women are different because they also had low platelet counts, a pattern he said is similar to what's been seen in Europe with the AstraZeneca vaccine.

Blood clots are typically treated with heparin, an anticoagulant drug, but using heparin for this type of blood clot can be dangerous. Marks said alternative treatments are needed, preferably by doctors experienced in treating blood clots.

“The issue here with these types of blood clots is that if one administers the standard treatment that we as doctors have learned to give for blood clots, one can actually cause tremendous harm or the outcome can be fatal," he said.

"So one needs to make sure that providers are aware that if they see people who have low blood platelets or if they see people who have blood clots, they need to inquire about a history of recent vaccination and then act accordingly in the diagnosis and management of those individuals.”

Reach the reporter at Alison.Steinbach@arizonarepublic.com or at 602-444-4282. Follow her on Twitter @alisteinbach.

Reach health care reporter Stephanie Innes at Stephanie.Innes@gannett.com or at 602-444-8369. Follow her on Twitter @stephanieinnes.

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