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Investigators Working To Determine Whether Johnson & Johnson Vaccine May Cause Blood Clots

NEW YORK (CBSNewYork) - Investigators are working feverishly to determine whether the Johnson & Johnson may cause serious brain blood clots in six women.

While that analysis proceeds, the FDA's pause in using the J&J vaccine continues.

As CBS2's Dr. Max Gomez reports, while the J&J vaccine pause came with little notice and may increase vaccine hesitancy, the White House coronavirus response coordinator defended the decision and subsequent transparency.


"We believe that by empowering Americans with data and facts, we will strengthen the public's trust in government and increase their confidence in the vaccines," Jeffrey Zients said.

Here's what we know so far about these cases:

  • These blood clot symptoms are different than the mild flu-like symptoms common for a day or two after any vaccine. These started 6-13 days after the J&J vaccine and include severe headache, leg or abdominal pain or shortness of breath
  • If you do develop these symptoms, go to a doctor or hospital immediately and tell your doctor that you recenetly got the J&J vaccine because the usual treatment for blood clots, Heparin, could be dangerous or even fatal
  • If you received the J&J vaccine a month or more ago, you are likely safe and don't need to worry - and you are also likely protected against COVID-19

At this time it's not at all clear whether women of child bearing age, smokers or those on oral contraceptives are at greater risk, although it's possible that these groups may now be advised against the J&J vaccine.

The cause of the blood clots seems to be an autoimmune overreaction that attacks platelets in the blood. Women are known to be more at risk for most autoimmune diseases and that may account for the fact that these clots have only been seen in women so far.

There is a possibility that this blood clot complication is comparable to complications seen in Europe with the AstraZeneca vaccine. Both use similar common cold viruses in their vaccines. Neither the Moderna nor the Pfizer vaccines have had any such reactions.


A Centers for Disease Control and Prevention advisory committee said Wednesday that more data on the blood clots needs to be done before deciding on the next steps of the vaccine.

They will reconvene in 7-10 days to re-evaluate.

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