CDC Recommends Pfizer and Moderna Vaccines Over Johnson & Johnson

Janssen vaccine

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Key Takeaways

  • The CDC now recommends Pfizer and Moderna mRNA COVID-19 vaccines over the Johnson & Johnson shot, following concerns about blood clots.
  • The J&J vaccine is linked to a rare but serious blood clotting problem called thrombosis with thrombocytopenia syndrome (TTS).
  • Protection from the Johnson & Johnson vaccine is still better than not getting a vaccine at all.

The Centers for Disease Control and Prevention (CDC) on Thursday recommended the Pfizer and Moderna COVID-19 vaccines over the Johnson & Johnson shot, citing concerns about the risk of rare but life-threatening blood clots.

The J&J vaccine, which is simpler to store and transport, is still available for people “who are unable or unwilling to receive an mRNA vaccine,” the agency said.

CDC advisers cited 54 documented cases of thrombosis with thrombocytopenia syndrome (TTS), a blood clotting condition. TTS is treatable, but complications can include heart attack and stroke. At least nine J&J vaccine recipients have died from TTS.

Around 16 million Americans have been received the J&J vaccine.

What Is Thrombosis With Thrombocytopenia Syndrome (TTS)?

TTS is a combination of thrombosis (when blood clots block blood vessels) and thrombocytopenia syndrome (a low number of platelets in the blood). This is a new syndrome, only identified after the introduction of adenovirus vector COVID-19 vaccines like J&J. It’s also referred to as vaccine-induced thrombotic thrombocytopenia (VITT).

"The U.S. supply of mRNA vaccines is abundant—with nearly 100 million doses in the field for immediate use," the CDC said in a statement, adding that some other countries have adopted similar recommendations for adenovirus vector vaccines like J&J and AstraZeneca.

In Canada, an mRNA vaccine should be offered first. Denmark took things one step further, completely halting the use of Johnson & Johnson shots because of blood clot risk.

Earlier this week, the Food and Drug Administration (FDA) officially revised the J&J vaccine fact sheet, indicating that anyone with a history of TTS following COVID vaccination should not receive this vaccine as a booster.


Adenovirus vector vaccines use a modified adenovirus—a virus that causes the common cold—as a vessel to deliver genetic material from the COVID-19 virus into the body.

Not the First Setback for J&J

In April, federal regulators temporarily paused the use of the J&J vaccine following six cases of cerebral venous sinus thrombosis (CVST), a type of blood clot in the brain.

The pause was lifted and a warning label was added to the vaccine. 

In July, the FDA added another warning label to the J&J vaccine for its potential to trigger an autoimmune disorder called Guillain-Barré Syndrome (GBS). At the time, about 100 cases had been reported. GBS can lead to full body-paralysis, though most people make a full recovery. 

What If You Received a J&J Vaccine?

If you received a J&J shot, you shouldn’t panic. Remember: The risk of experiencing this side effect is very low. According to CDC data, only 3.83 TTS cases were reported for every million doses of the J&J vaccine administered. 

TTS by the Numbers

CDC data shows the following statistics on the identified TTS cases after J&J vaccination:

  • Age range: 18-70 years old (median age is 44.5)
  • Among the 54 cases, 27 were women and 17 were men.
  • 83% of cases are in White people.
  • 54% of the TTS cases feature a cerebral venous sinus thrombosis (CVST).

The CDC advisory panel also reported that the median time from vaccination to symptom onset was nine days, with the longest record being 18 days after vaccination. If you’re two or three weeks past the date of your vaccination, you’re likely in the clear.

What Symptoms Should You Look For?

According to the CDC, symptoms of TTS can manifest itself in several ways:

  • Pain and swelling in an extremity
  • Chest pain
  • Numbness or weakness on one side of the body
  • Sudden change in mental status

If you experience any of the above symptoms within three weeks of receiving a COVID-19 vaccine, contact a healthcare provider.

How Is TTS Treated?

TTS treatment is different from that of standard blood clot. The low levels of blood platelets associated with this condition mean that anticoagulation medication like Heparin could worsen the condition.

Other blood thinners, like bivalirudin or argatroban, can be used instead. Bivalirudin was used to successfully treat a Colorado woman experiencing TTS in April.

What This Means For You

If you’re deliberating about which COVID-19 vaccine or booster to get, consider seeking out Pfizer or Moderna. But if J&J is much easier to come by, know that it’s still an option. The risk of complications from J&J is still extremely low. 

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. HealthDirect. Thrombosis with thrombocytopenia syndrome (TTS).

  2. Centers for Disease Control and Prevention. Understanding Viral Vector COVID-19 Vaccines.

  3. U.S. Federal Drug Administration. Coronavirus (COVID-19) Update: July 13, 2021.

  4. Advisory Committee on Immunization Practices (ACIP). Updates on Thrombosis with

    Thrombocytopenia Syndrome (TTS).

  5. Centers for Disease Contorl and Prevention. Updates on Thrombosis with Thrombocytopenia Syndrome (TTS).