The Johnson & Johnson vaccine and blood clots

The US is temporarily halting giving this vaccine, pending further study, because of the potential danger of blood clots. Six women developed a rare form of blood clots after receiving this vaccine and one died.

The acting FDA chief, Janet Woodcock, said: “We’re recommending this pause while we work together to full understand these events.” The decision was taken in coordination with the CDC.

US health agencies have recommended states pause the administration of the Johnson & Johnson coronavirus vaccine, after reports of rare and severe blood clots emerged in six women. More than 6.8m doses have been administered nationally.

The concerns mirror those of drugs agencies in Europe and Australia over the AstraZeneca vaccine, which has not been authorized in the US. There have been no significant safety concerns raised about the two other vaccines that make up the majority of US supply, from Pfizer-BioNTech and Moderna.

Woodcock said: “Right now, I’d like to stress these events appear to be extremely rare. However, Covid-19 vaccine safety is a top priority for the federal government. We take all reports of adverse events related to the vaccine very seriously.”

The FDA and CDC said in a joint statement: “People who have received the J&J vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their healthcare provider.”

Over six million J&J vaccines have been given so the incidence rate of clotting is tiny, smaller than the risk of getting seriously ill by contracting covid-19. It is not yet clear if the vaccine is even the cause of the clotting. So why the pause?

One can understand the problem for the FDA and CDC. When they learned of the clot cases they had to reveal its existence for the sake of transparency. Hiding such information is never a good idea because not only would it be wrong but because if it gets out (and you can be pretty sure it will), that will ruin any credibility that these organizations have built up with the public. But once you reveal the existence of the potential problem, your options become limited. You cannot just announce the problem and do nothing. If you pause the use of the vaccines saying that you are going to study the issue, it makes people comfortable that you are talking safety seriously. On the other hand, it will likely increase vaccine hesitancy, especially among those who were already on the fence. And it gives also more ammunition to the anti-vaxxers. But I think they had not choice but to announce the pause until they have looked more closely at the evidence.

As I mentioned some time ago, I received the Johnson & Johnson vaccine, so I was interested in this news but not particularly worried. Partly this is because I received mine five weeks ago, past the time window of three weeks that people are supposed to be alert for clotting symptoms and I also have not had any of the associated symptoms. But also partly because at my age there are a whole host of small risk items from which I could die on any given day. This is just one more to add to the list, hardly worth losing sleep over.

Risks need to be evaluated compared with other risks and for me the risk of getting covid-19 outweighs the risks of the vaccine. And the conclusion of the experts is still the same: take the first vaccine you are offered.


  1. jrkrideau says

    I think the various regulatory agencies are between caught between Scylla and Charybdis.

    They have a duty to investigate any issues. If they act immediately and raise alarms they scare people. If they spend a bit more time investigating the anti-vaxers hear about in it is ammunition for their deranged campaigns.

    personally I’ll take whatever is on offer.

  2. morsgotha says

    As I understand the Astra Zenica one has the same potential problem. Here in the UK the doctors on the BBC explained the dangers of the blood clot versus covid for all age groups.

    I’m due soon for a vaccine, it will likely be the AZ one. I am more worried about not getting it.

  3. raven says

    This is actually a disaster for the entire world.

    1. The AstraZenica and J&J vaccines are similar but slightly different.
    The AZ one uses a chimpanzee adenovirus as vector, while J&J uses Adenovirus 26.
    This clotting problem is starting to look like it is vector specific.
    2. Latest headline businessinsider
    “Don’t start doubting the Pfizer or Moderna vaccines — after 185 million doses, there are no red flags about blood clots”
    They haven’t seen this blood clotting problem with the mRNA vaccines.

    The AZ and J&J vaccines were supposed to be the world’s vaccines. Easily made, stable, one shot, and inexpensive. This clotting problem is calling them into question especially since there are alternatives.
    If they don’t go further, this puts the world vaccination effort back by a year or two at the least.
    With billions of people and the Covid-19 virus circulating among them, this sets up a possibility for more evolved and pathogenic variants to show up eventually here.

    The joke is that there aren’t Covid viruses 1-18.
    There may however be a Covid-22 virus outbreak.

  4. raven says

    Quite a few Covid-19 vaccine projects have so far just failed, including two from Merck and one from Sanofi.
    The Chinese vaccines work but apparently not as well as the mRNA ones.
    We really need a good stable and low cost vaccine for the rest of the world.
    One possibility is to try another inactivated vector vaccine, maybe Newcastle disease virus or AAV.

    The protein subunit one from Novax is so far looking like it might be a third viable vaccine.

  5. Holms says

    Six blood clots formed after how many doses of this vaccine…? 6.8 million. Less than one in a million, and when people are perhaps over-alert to subsequent symptoms. Given the fact that blood clots can already form in otherwise healthy people -- especially in the elderly (who were the first to become eligible) -- I suspect this is just hair-trigger vigilance. Regarding the European pause, those political leaders that did so were subsequently broadly criticised for that action by many health professionals, who pointed out the above but with some added asperity.

  6. robert79 says

    Problems like this are what inspired the original philosophical trolley bus problems.

    Do you let a deadly disease rampage on killing thousands, or do you vaccinate, thereby killing hundreds through the extremely rare side effects — people who would not have died if you had decided not to vaccinate.

    I think these trolley bus problems are absolute nonsense, since it’s *never* that binary, there is always another option, which is what’s going on right now: pause for a bit, figure out what’s going on.

  7. mnb0 says

    “risks need to be evaluated compared with other risks”
    Sure, but unless they are trained it humans do badly at probability calculation. Instead they rely on instinct; you can ask any psychologist. Politicians realize this too; they know they will be blamed for vaccin related deaths (no matter how weak the correlation) and won’t be rewarded for the lives they save by pushing the vaccination program.

  8. Mano Singham says

    Tabby @#6,

    I would be cautious about taking any anti-clotting stuff on your own. Apparently the FDA is warning physicians not to use the standard anti-clotting medicine to treat the J&J clots because it makes it worse. I have not heard anything about aspirin but you may want to check with a doctor or wait and see until the investigation of the J&J vaccine is carried out.

  9. Deepak Shetty says

    Day 5 of J&J for me -- but if I dont comment any more you know what happened.

    Most of the folks who have taken the J&J understand its very low risk but the fact that other vaccines are available with a higher efficacy rate has most of them saying they wouldnt have taken it if they knew about it. The comparison of probability of blood clots with J&J v/s blood clots with Covid hence has no meaning because now everyone wants the Moderna/Pfizer.

  10. Jazzlet says

    Holms @5

    The clots have mostly occurred in younger women not the elderly. The risks of catching COVID-19 are far greater, in fact the risk of clots from taking the pilll is far greater -- one in a hundred thousand -- but generally people are really bad at risk assessment.

  11. Sam N says

    Another J&J vaccinated here. About day 5ish, too. I was more afraid driving to and from the clinic than this exceptionally rare side effect. Which is to say: not at all.

  12. file thirteen says

    My heart goes out to the families of those who will die as a result of this delay. The silver lining on this cloud is that this is great ammunition against the anti-vaxx conspiracy theorists. That the use of a vaccine is delayed because of a one-in-a-million side effect shows how much care is taken with the development and use of these vaccines. Nutters will be nutters, but most humans do have some capacity for reason.

  13. file thirteen says

    @Mano #9

    Apparently the FDA is warning physicians not to use the standard anti-clotting medicine to treat the J&J clots because it makes it worse.

    The clots may have resulted due to the immune system trying to fight something that has penetrated the blood-brain barrier, meaning that they may not be the problem, just the only visible symptom. It’s known that clearing out the clots that form in Alzheimers patients’ brains does not affect the progression of that disease.

  14. says

    I think it’s crazy -- it’s a 1 in 1 million risk. Americans simultaneously want to whine that they are being oppressed if they’re asked to wear a mask, but god forbid a 1 in 1 million risk of blood clots! Can we make up our minds if we’re badasses or snowflakes, already?

    There may be a statistical signal on the J&J but it’s also possible co-morbidity. If you take 1 million Americans aged 60+, a significant number of them are going to die of obesity-related/alcohol-related/opiate-related/just plain stupid causes during the time of the study. As I mentioned elsewhere, I was diagnosed with deep vein thrombosis on Monday, and have been dealing with the fallout from that -- but that was 2 weeks after my second Pfizer COVID-19 vaccine (and I had a shingles vaccine, too) Do I think it’s related? Nah, it’s just luck. Sometimes luck is the easiest explanation for risk.

  15. xohjoh2n says

    @various above

    The current word on the (medical) street is that the numbers are convincingly above baseline; barely, but this looks like a real effect. Furthermore it’s similar to another rare condition seen as a complication of heparin treatment, Heparin Induced Thrombocytopenia (HIT). The key sign there is the paradoxical combination of reduced platelet counts (which *ought* to result in reduced blood clotting) paired with, in fact, increased clotting activity. (Because, they say, the immune system has somehow started to attack components of the clotting cascade itself.)

    The treatment for that (and what also appears to work for the new vaccine related cases) is fairly specific -- it is not the normal first-line blood clot treatment as that appears to make things much much worse. The important thing is to remain vigilant and if you happen to turn out to be one of the one-in-a-million people affected, seek proper medical help quickly. Because it can be successfully treated, but will go seriously and rapidly wrong if untreated or wrongly treated.

    (My first shot now scheduled for Monday. It’ll most likely be AZ. I’ll be taking it.)

  16. blf says

    If things proceed according to plan here in France, my vaccination will very probably be either J&J or AZ. I don’t care which, the struggle is to actually be vaccinated — the situation / blocks have changed recently, and I am still working through them…

  17. raven says

    FWIW, the recommended treatment for these rare clotting cases is the same as HIT, heparin induced thrombocytopenia, which they resemble.
    The recommendations from the American Society of Hematology are long but for acute cases…

    Management of the acute phase of HIT
    Recommendation 3.1.
    In patients with acute HIT complicated by thrombosis (HITT) or acute HIT without thrombosis (isolated HIT), the ASH guideline panel recommends discontinuation of heparin and initiation of a non-heparin anticoagulant (strong recommendation, moderate certainty in the evidence about effects ⊕⊕⊕◯). When a non-heparin anticoagulant is being selected, the ASH guideline panel suggests argatroban, bivalirudin, danaparoid, fondaparinux, or a direct oral anticoagulant (DOAC) (conditional recommendation, very low certainty in the evidence about effects ⊕◯◯◯).

    The key point is to avoid the usual standard which is heparin, and use non-heparin anticoagulants.
    The other key point is to be aware of the syndrome and treat it as quickly as possible.

  18. jrkrideau says

    @ 14 file thirteen
    The silver lining on this cloud is that this is great ammunition against the anti-vaxx conspiracy theorists.

    True among some vaccine hesitant but the US anti-vaxers are already writing their screeds claiming the death rate is really 50% and it is a conspiracy between the CDC and big Pharma to cover up the true rate.

    Health Canada has approved the AstraZeneca-Oxford vaccine for general use today.
    After safety review, Health Canada says people shouldn’t hesitate to get AstraZeneca vaccine

  19. xohjoh2n says

    @18 they’re also recommending immunoglobulin injections, because while removing the existing clots is important, it is also important to damp down the immune response that is causing them in the first place.

  20. file thirteen says

    @jrkrideau #19

    the US anti-vaxers are already writing their screeds claiming the death rate is really 50%

    Doesn’t seem that hard to verify. “Name them”.

  21. Katydid says

    For some anecdata: I’ve heard from whackadoo coworkers that the death rate from the vaccines is far higher than the death rate from actual Covid. Clearly I work with a lot of whackadoos and we’re all crammed into overstuffed buildings and using the same door handles and bathrooms and water fountains. This worries me greatly.

  22. Katydid says

    According to Dr. Fauci and some medical facts thrown around yesterday, the rare (less than one-in-a-million) reaction has happened to women in their childbearing years (I think the range was 19 -- 48). One area of speculation is that the reaction is related to hormones; blood clots are a rare side effect of pregnancy and also the birth control pill, and are more likely to happen in women who are smokers. We know if a person gets COVID, their chance of dying is certainly more than one-in-a-million.

    The human body and human immune system can vary greatly from person to person I don’t think it’s possible to create a medical treatment that 100% of the human population tolerates without side effects. IMO, the steps to avoid the side effect might come down to “women in this age range ho are concerned about blood clots should take the Moderna or Pfizer shot”

  23. raven says


    That could be significant because, according to the CDC, “The AstraZeneca and Johnson & Johnson vaccines both use an adenovirus vector” to deliver instructions, in the form of genetic material, to a cell. “These vaccines are different from the Pfizer and Moderna vaccines, which are mRNA-based vaccines,” notes the agency’s statement.
    “These types of reactions — blood clots in combination with low platelets — are not being seen with the authorized vaccines from Pfizer and Moderna.”

    More and more this rare blood clotting is starting to look not vaccine related but vector related.
    It seems to be a property of the Adenovirus vectors.

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