Earlier this month the U.S. Facilities for Illness Management and Prevention really helpful a pause in the usage of the Johnson & Johnson (J&J) COVID-19 vaccine following reviews that, inside two weeks of getting it, six girls developed blot clots, and one among them died. About 6.8 million individuals had acquired that vaccine at the moment. The day after it issued the advice, the company convened a gathering of the Advisory Committee on Immunization Practices (ACIP) to go over every case and decide methods to proceed. ACIP determined to not raise the pause till it had extra knowledge. The committee met once more at present to debate the blood clots and voted to advocate resumption of the vaccine’s use in individuals age 18 and older. The committee additionally really helpful that the Meals and Drug Administration add a warning concerning the uncommon threat of blood clots in some individuals. An identical sample of clots has been noticed in a really small proportion of people that acquired the AstraZeneca vaccine in Europe. European regulators have known as for the J&J vaccine to hold a warning however haven’t restricted its use.
Wilbur Chen, an infectious illness physician-scientist on the College of Maryland College of Drugs’s Heart for Vaccine Growth and World Well being, is a member of ACIP. He mentioned the dangers, signs and attainable causes of the blood clots with Scientific American forward of ACIP’s second assembly.
[An edited transcript of the interview follows.]
What’s the estimated threat of those uncommon blood clots amongst individuals who have gotten the Johnson & Johnson vaccine?
We now have incomplete knowledge as of [April 21], however it seems like the danger is lower than one in 1,000,000 proper now. Which will change, and I believe we are going to get extra readability on these numbers—each by way of the variety of circumstances and the full variety of vaccines administered so far. [Editor’s Note: At the ACIP meeting on April 23, Tom Shimabukuro of the CDC’s COVID-19 Vaccine Task Force reported that as of April 21 there have been a total of 15 confirmed cases of this blood clotting condition among nearly eight million doses administered. All of the cases were in women, and the highest risk was among women ages 30 to 39, among whom the rate was 11.8 per million.]
Is there any hyperlink between diminished vaccine effectiveness and blood clots?
No, the effectiveness of the vaccines has not been challenged by these circumstances in any way.
How are these blood clots totally different from different blood clots?
Blood clots are shaped by platelets, which bind collectively to type a clot, and usually numerous them are wanted to try this. The clots seen with the Johnson & Johnson vaccine shaped even in sufferers who had low platelet counts of their bloodstream. That mixture is uncommon. Usually, when you’ve gotten actually low platelet counts—a situation known as thrombocytopenia—you even have issues with with the ability to type clots, and you’ll develop ongoing bleeding that’s arduous to cease. Moreover, we’re seeing this phenomenon of clots forming in severe locations such because the mind, the lungs, the legs or the stomach, even though platelet counts are actually low. That’s a really distinctive phenomenon. The closest factor we’ve seen is a uncommon situation known as heparin-induced thrombocytopenia (HIT). [Editor’s note: HIT Is a condition in which the anticoagulant medication heparin lowers platelet counts. It increases the risk that blood clots will develop—a condition known as heparin-induced thrombotic thrombocytopenia, or HITT.] We now have additionally seen an identical sort of phenomenon with the AstraZeneca vaccine.
What are the signs of those blood clots in individuals who have had the Johnson & Johnson vaccine?
They’re totally different than among the signs individuals expertise proper after getting their vaccination, similar to fatigue, soreness on the injection website or joint aches. These types of issues are frequent, they seem shortly after the vaccination, and so they normally go away after about three to 5 days. The signs associated to the blood clots have a tendency to seem a few week or two after the vaccination after which proceed to worsen. A headache that received’t go away is one symptom. Now, for those who’ve simply exerted your self by going for a run or gardening within the solar on a scorching day, you may need a headache, fatigue, leg or stomach ache, or shortness of breath, however for those who sit in a cool spot and drink some water, these will most likely go away. However if you’re experiencing these signs, and so they proceed to worsen even though you’re doing issues that may usually make you’re feeling higher, that may be extra regarding.
What’s the really helpful remedy for these blood clots?
We’re not exactly certain but, however it sounds prefer it shouldn’t be heparin due to the danger of HIT. There are comparable, dearer blood-thinner drugs that might be able to deal with these blood clots. An April 12 research within the BMJ really helpful the usage of non-heparin anticoagulants together with immunoglobulins—antibodies produced by white blood cells—to deal with vaccine-induced clotting.
What could be inflicting the blood clots?
We don’t know for certain. However our main speculation is that they could be related to this antibody towards the protein platelet issue 4, PF4 for brief. That antibody appears to be implicated within the AstraZeneca clots and in addition is the mechanism for heparin-induced thrombotic thrombocytopenia, so the proof all appears to be pointing in the identical path. HITT Is definitively linked to that antibody. And we’ve got some proof that it could be implicated within the AstraZeneca and Johnson & Johnson clotting circumstances. Hopefully, as we get extra proof, it can make us extra assured in that mechanism.
Are there any similarities between the J&J and AstraZeneca circumstances?
There are similarities within the timing of after they occur and the presentation of signs. It’s uncommon to have clots within the face of thrombocytopenia, or low platelet counts. In order that appears to be pointing to one thing comparable. And the 2 vaccines themselves are comparable in that they’re each made with adenovirus vectors—innocent modified viruses that ship directions to the physique on methods to battle COVID-19. So that could be a commonality, however there are different vaccines in use across the globe that additionally use adenovirus vectors, such because the Sputnik V vaccine, as nicely. [Editor’s Note: No blood clots have yet been reported to be linked to the Sputnik V vaccine.]
Why does this clotting seem like extra frequent in girls between the ages of 18 and 48?
We’re unsure. It may merely be associated to the truth that extra girls are getting vaccinated than males proper now. Or it’s attainable that it was a coincidence that girls occurred to report these. It could possibly be a statistical fluke. However to find out that, we’d like extra info. It could be that we uncover there’s a hyperlink between intercourse and chance of creating clots, however my intestine feeling is that that won’t be the case. We’d like extra knowledge to know for certain.
Is there a threat of elevated vaccine hesitancy because of the clot-related pause?
I believe reporting these circumstances might lead to extra vaccine hesitancy initially. But when we had tried to attenuate or ignore these occasions or delayed the reporting, I believe that may have had implications and really fed into mistrust and concern and, in the long run, lead to much more hesitancy. After we had been first launching the Pfizer vaccine, we heard of some preliminary circumstances of anaphylaxis [allergic reactions] in individuals who had gotten it. But it surely turned out to be very uncommon, and concern of that appears to have subsided. I prefer to imagine that’s as a result of public well being officers had been very clear and communicated the danger of anaphylaxis early on. And now we monitor individuals for 15 to half-hour after vaccination to scale back that hazard as nicely. There will probably be different points, definitely, with mistrust and hesitancy and delay. However the extra we speak via these points, the extra it helps the general public perceive them.
Editor’s Observe (4/23/21): This text has been up to date after posting to offer info from the April 23 ACIP assembly.