j & j vaccine bottle in handsPhoto: ROB ENGELAAR / ANP / AFP (Getty Images)

Six out of over 6 million people who received the Johnson & Johnson / Janssen COVID vaccine have developed a rare type of blood clot. As a result, the FDA and CDC did announced a break in using this vaccine. The break will likely only last a few days.

The reason for the hiatus, according to spokespersons for the FDA and CDC, is to give health care providers across the country time to look out for this rare complication and get the CDC approved Advisory Committee on Vaccination Practices Review the evidence and decide whether to change their recommendations on who should receive the vaccine.

What is the rare complication?

The six cases were from cerebral venous sinus thrombosisA type of stroke that occurs when a clot prevents blood from draining from the brain. This is already a rare condition (2 to 14 cases per million people per year according to the CDC), but what is unusual here is that all six people had CVST along with low platelet counts. Platelets are blood cells that are involved in clotting; Usually CVST occurs in people with normal platelet counts.

These cases are unusual in that they involved CVST and low platelet counts and occurred 6 to 13 days after receiving the Johnson & Johnson vaccine. They are of particular concern because the normal treatment for blood clots is to use anticoagulants such as heparin. However, heparin can be harmful to people with CVST. Therefore, the FDA and CDC want providers to be aware of this rare disease and know that they need to treat it differently.

The people who developed this rare condition were all women between the ages of 18 and 48 years. One case was fatal and one person is in critical condition. It is not yet known whether age, gender, or other medical conditions can predispose a person to developing this complication. We may find out more in the coming days.

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What if i just got the J&J vaccine?

If you received the vaccine a month or more ago, your chances of developing this condition are extremely slim. There are no known cases that started more than 13 days after vaccination.

If you have had the vaccine in the past few days then there is nothing to worry about flu-like symptoms that follow– including headache, tiredness and fever – if they occur within the usual time (a few days or up to about a week after vaccination).

If you’ve had the vaccine in the past few weeks, see a doctor if you develop any of the following symptoms:

  • Strong headache
  • Severe stomach ache
  • Pain in the legs
  • shortness of breath

If you are seeking care, be sure to let your provider know that you received the Johnson & Johnson vaccine and the date you received it. The FDA and CDC state that they are making “aggressive contacts” to ensure all vendors know they are looking for this rare complication.

Is that a problem with the other vaccines?

There is no evidence that these rare blood clots occur in people who received Moderna or Pfizer vaccines. To date, 121 million Americans have received at least one dose of a COVID-19 vaccine, with J&J accounting for between 6 and 7 million of them. If this complication had occurred with the other two vaccines, we would probably have noticed by now. (That doesn’t guarantee they’re completely safe, but the odds are very good.)

However, the AstraZeneca vaccine has been linked to rare blood clots. Both the AstraZeneca and J&J vaccines use an adenovirus vector. One hypothesis is that, on very rare occasions, a person’s immune system may respond to the vector by attacking their own body’s platelets. CDC advisors plan to review current and past research on these and other adenoviral vaccines to find out what is going on.

What does a “pause” actually mean?

The vaccine is not being recalled and is still approved for use in an emergency. The break is a “recommendation, not a mandate,” said Peter Marks, director of the FDA’s Center for Biological Research and Evaluation, at a press conference. If you discuss the vaccine with your provider and the provider agrees that the benefits to you outweigh the risks, they can still give the vaccine. But the recommendation is to hold back for the time being.

If you have an appointment in the next few days, you will likely be asked to reschedule or you may be offered one of the other two vaccine formulations available. If your appointment is longer than a few days, it’s probably best to wait and see.

The CDC Advisory Committee, ACIP, will meet tomorrow to discuss what is currently known on the matter and to consider whether recommendations should be changed. We may know more soon.

Janet Woodcock, Acting Commissioner of the FDA, said in a press conference that “the time frame of the break depends on what we learn in the next few days,” but also, “We expect this to be a matter of days of break.”

How does this compare to the rate of blood clots as a complication of birth control?

Pulmonary embolism and deep vein thrombosis (two types of blood clots that are not the same as CVST) occur in 0.3% to 1% of people who have been taking oral contraceptives containing estrogen for 10 years. Blood clots can also occur as a result of pregnancy. Therefore, the risk of blood clots with birth control pills has long been known, understood, and balanced against the other risks and benefits of taking or not taking these contraceptives.

I only mention this because several people on social media have found a one-in-a-million risk of blood clots from the vaccine compared to the risk we already know and (in many cases) accept from birth control pills have faded.

Numerically that is correct. However, the complication of the vaccine is noteworthy because it is new, because providers need to know that it cannot be treated with standard blood clot treatments, and because it may be possible to avoid the risk altogether by using a different vaccine instead administered.

What does this tell us about vaccine safety in general?

For people who are skeptical of vaccines, the news of this frightening complication seems to be evidence that the vaccines are dangerous.

It is worth noting, however, that the vaccine was on hold because of a 1: 1 million complication and the pause came very quickly when regulators found out about it. Compare this to the misinformation widely shared, which uses fictional or out of context stories to imply that people are falling dead from the vaccine all the time and nobody cares.

Interrupting the vaccine to investigate a rare side effect is a sign that regulators are genuinely paying attention and being transparent about the process of investigating what is going on.

What happens next?

Since the complication can appear a week or two after receiving the vaccine, don’t be surprised if more cases arise in the next week or so. (It’s “too early to speculate how many,” Marks said at the press conference.)

Expect to hear more after the ACIP meeting tomorrow and as more information comes out. The CDC and FDA will likely make an announcement when they decide it is time to resume vaccination, or, less likely but still possible, when they decide the evidence changes recommendations or withdraws it assist with the emergency approval of the vaccine.

If you’d like to see the ACIP meeting, it’s on Wednesday, April 14th, from 1:30 pm to 4:30 pm Eastern Time. with this link.