At least six people out of over 6 million who have received the Johnson & Johnson/Janssen COVID vaccine have developed a rare type of blood clot. As a result, the FDA and CDC have announced a pause in the use of this vaccine. The pause is likely to last at least another week.
The original reason for the pause, spokespeople for the FDA and CDC said, was to allow time to get the word out to healthcare providers across the country to look out for this rare complication, and to allow the CDC’s advisory committee on vaccination practices to review the evidence and decide whether to change their recommendations about who should get the vaccine.
The committee met on April 14, and felt they did not have enough information on the risks and benefits of the vaccine to either change recommendations or to recommend that vaccinations be resumed. They plan to reconvene in another week—perhaps around April 21, although the meeting has not yet been scheduled—when the pause could potentially be lifted.
In the meantime, Johnson & Johnson stated in a press release that they will delay the rollout of the vaccine in Europe (where it has been authorized but is not yet in use), and that they are pausing vaccinations in ongoing clinical trials that use this vaccine.
What is the rare complication?
The six cases were of cerebral venous sinus thrombosis, a type of stroke that occurs when a clot prevents blood from draining out of the brain. This is already a rare condition (2 to 14 cases per million people per year, according to the CDC) but what’s unusual here is that all six people had CVST together 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 because they involved CVST and low platelet counts, and occurred 6 to 13 days after receiving the Johnson & Johnson vaccine. They are particularly concerning because the normal treatment for blood clots is to administer anticoagulants like heparin—but heparin can be harmful to people with CVST, so the FDA and CDC want providers to be aware of this rare condition and to know they must treat it differently.
The first six people reported to experience this rare condition related to the vaccine were all women between the ages of 18 and 48. One case was fatal, and one person is in critical condition. It is not yet known whether age, gender, or other medical conditions may predispose a person to developing this complication. We may find out more in the coming days.
In the ACIP meeting on April 14, a representative from Janssen noted that a similar blood clot had occurred in a 24-year-old man in September, during the clinical trials, and they had also recently had a report of a blood clot of this type in a 59-year-old woman.
Please note that COVID-19 itself has a high risk of blood clots (of a different type). As physician Megan Ranney points out on Twitter, the rate of clots with COVID may be as high as 20% for those who are hospitalized.
What if I just got the J&J vaccine?
If you got the vaccine a month ago or longer, your chances of developing this condition are extremely low; there are no known cases that began more than 13 days after vaccination.
If you got the vaccine in the past few days, there’s no need to worry about flu-like symptoms that follow—which include headache, fatigue, and fever—if they occur in the usual timeline (a few days or up to about a week after vaccination).
If you got the vaccine within the past few weeks, seek medical care if you develop any of the following:
- Severe headache
- Severe abdominal pain
- Pain in the legs
- Shortness of breath
When you seek care, make sure to tell your provider that you got the Johnson & Johnson vaccine, and the date when you got it. The FDA and CDC say they are doing “aggressive outreach” to make sure all providers know to be on the lookout for this rare complication.
Is this an issue with the other vaccines?
There is no indication of these rare blood clots occurring in people who got Moderna or Pfizer vaccines. So far, 121 million Americans have gotten at least one dose of a COVID-19 vaccine, with J&J accounting for between 6-7 million of that number. If this complication occurred with the other two vaccines, we probably would have noticed by now. (That doesn’t guarantee that they’re completely safe, but the odds are very good.)
The AstraZeneca vaccine, however, has been associated with rare blood clots. (It is not used or authorized in the US, but other countries have noted this association.) Both the AstraZeneca and the J&J vaccines use an adenovirus vector. One hypothesis is that in very rare cases, a person’s immune system may react to the vector in a way that leads it to attack their own body’s platelets. Advisors to the CDC are planning to look at current and past research on these and other adenoviral vaccines to figure out what’s going on.
What does a “pause” mean, anyway?
The vaccine is not being recalled, and it is still authorized for emergency use. The pause is a “recommendation, not a mandate,” Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a press call. If you discuss the vaccine with your provider and the provider agrees that the benefits to you outweigh the risks, they may still administer the vaccine. But the recommendation is to hold off for now.
If you have an appointment in the next week, chances are you’ll be asked to reschedule, or you may be offered one of the other two vaccine formulations that are available. If your appointment is more than a week out, it’s probably best to wait and see.
How does this compare to the rate of blood clots as a complication of birth control?
Pulmonary embolisms and deep venous thrombosis (two types of blood clots that are not the same as CVST) occur in 0.3% to 1% of people who take estrogen-containing oral contraceptives for 10 years. Blood clots can also occur as a result of pregnancy, so the risk of 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 have noted on social media that a one-in-a-million risk of clots from the vaccine pales in comparison to the risk that we have already known and, in many cases, accepted from birth control pills.
Numerically, that’s accurate. But the vaccine complication is noteworthy because it is new, because providers need to know it cannot be treated with the usual treatment for blood clots, and because it may be possible to avoid the risk altogether by administering a different vaccine instead.
What does this tell us about vaccine safety in general?
For people who have been skeptical of vaccines, news of this scary complication may seem like proof that the vaccines are dangerous.
But it’s worth noting that the vaccine was paused for a one-in-a-million complication (or two per million, if you consider that about 3 million doses have been given too recently to detect the complication), and the pause occurred very quickly once regulators found out about it. Contrast that with the misinformation that is often passed around, which uses fictional or out-of-context stories to imply that people are dropping dead from the vaccine all the time and nobody cares.
Pausing the vaccine to investigate a rare side effect is a sign that regulators are indeed paying attention, and that they’re being transparent about the process of investigating what is going on.
It’s also worth noting that the cases came to the CDC’s and FDA’s notice through VAERS, a database where anybody can enter a report of health complications that occurred after a vaccine. While anti-vaccine activists often misuse this database to claim that deadly complications are being ignored, the truth is that even these few cases of a serious complication were detected through VAERS and regulators acted quickly to gather more information and take action.
What happens next?
Since the complication can occur a week or two after receiving the vaccine, don’t be surprised if a few more cases turn up in the next week or so. (It’s “too early to make any speculation on how many,” Marks said in the press call.)
Expect to hear more after the next ACIP meeting next week, and as more information comes out. The CDC and FDA will likely make an announcement when they have decided it’s time to resume vaccination or, less likely but still possible, if they decide that the evidence supports changing recommendations or rescinding the vaccine’s emergency authorization.
Updated April 13, 2021 at 12:18pm to note that the risk of clots from COVID itself overwhelms the risk from any vaccine, and that the AstraZeneca vaccine is not currently used in the U.S. It was updated again on April 15, 2021 to note the results of the ACIP meeting, which extended the pause.