U.S. health authorities came close to simply warning about a blood-clotting risk from Johnson & Johnson’s Covid-19 vaccine, but they decided to recommend pausing use out of concern doctors would improperly treat the condition, people familiar with the matter said.
Over the previous four weeks, U.S. health officials had become alarmed about similar blood-clotting conditions in Europe involving a Covid-19 vaccine from AstraZeneca PLC, the people said. The officials dug into a U.S. vaccine safety database and identified the cases of great concern, but they debated what action to take.
By the night of April 12, the officials resolved that urgent action was needed, the people said. Four of six women in the U.S. who developed the clots days after vaccination had initially been given blood thinner heparin, according to the federal Centers for Disease Control and Prevention. Its use could have worsened the patients’ condition, the people said.
Using an electronic health records network we estimated the absolute incidence of cerebral venous thrombosis (CVT) in the two weeks following COVID-19 diagnosis(N=513,284), or influenza (N=172,742), or receipt of the BNT162b2 or mRNA-1273 COVID-19 vaccines(N=489,871). The incidence of portal vein thrombosis (PVT) was also assessed in these groups, as well as the baselineCVTincidence over a two-week period. The incidence of CVT after COVID-19 diagnosis was 39.0 per million people (95% CI, 25.2–60.2). This was higher than the CVT incidence after influenza (0.0 per million people, 95% CI 0.0–22.2, adjusted RR=6.73, P=.003) or after receiving BNT162b2 or mRNA-1273 vaccine (4.1 per million people, 95% CI 1.1–14.9, adjusted RR=6.36, P<.001). The relative risks were similar if a broader definition of CVT was used. For PVT, the incidence was 436.4 per million people (382.9-497.4) after COVID-19, 98.4 (61.4-157.6) after influenza, and 44.9 (29.7-68.0) after BNT162b2 or mRNA-1273. The incidence of CVT following COVID-19 was higher than the incidence observed across the entire health records network (0.41 per million people over any 2-week period). Laboratory test results, available in a subset of the COVID-19 patients, provide preliminary evidence suggestive of raised D-dimer, lowered fibrinogen, and an increased rate of thrombocytopenia in the CVT and PVT groups. Mortality was 20% and 18.8% respectively. These data show that the incidence of CVT is significantly increased after COVID-19, and greater than that observed with BNT162b2 and mRNA-1273 COVID-19 vaccines. The risk of CVT following COVID-19 is also higher than the latest estimate from the European Medicines Agency for the incidence associated withChAdOx1 nCoV-19 vaccine (5.0 per million people, 95% CI 4.3–5.8). Although requiring replication and corroboration, the present data highlight the risk of serious thrombotic events in COVID-19, and can help contextualize the risks and benefits of vaccination in this regard.
Author(s): Maxime Taquet, Masud Husain, John R Geddes, Sierra Luciano, Paul J Harrison
A study by Oxford University found the number of people who receive blood clots after getting vaccinated with a coronavirus vaccine are about the same for those who get Pfizer PFE, 2.43% and Moderna MRNA, 6.67% vaccines as they are for the AstraZeneca AZN, -0.16% vaccine that was produced with the university’s help. According to the study, 4 in 1 million people experience cerebral venous thrombosis after getting the Pfizer or Moderna vaccine, versus 5 in 1 million people for the AstraZeneca vaccine. The risk of getting CVT is much higher for those who get COVID-19 — 39 in a million patients — than it is for those who get vaccinated. AstraZeneca’s vaccine use has been halted or limited in many countries on blood clot concerns.
Last week Austria, Norway, Denmark, and Iceland all suspended the administration of the Oxford-AstraZeneca COVID-19 vaccine, citing reports of blood clots occurring in a few folks who had been inoculated with it. Ireland, France, Germany, Italy, Spain, Thailand, and the Netherlands have now joined them.
“There is no causal effect established or anything like that yet,” Irish Prime Minister Micheal Martin told CNBC, “but as a precautionary move in line with the precautionary principle and in an abundance of caution, our clinical advice was to pause the program whilst the EMA does a review of this.”
The precautionary principle is an ideological construct that eschews risk-benefit evaluations and essentially requires that all new technologies be somehow proved entirely risk-free before they can be used.
