Al Roker reveals he’s hospitalised for blood clot in leg, lungs amid absence from ‘Today’ show

The cascade of decisions to pause the use of AstraZeneca's vaccine, mainly by European countries, followed reports of four serious cases in Norway, which were described among health workers under age 50 who received the vaccine. Most developed clots or bleeding abnormalities and had low platelet counts, health authorities there said. Two of them have died from brain hemorrhages, and the other two are hospitalized. The death of a 60-year-old woman in Denmark and of a 57-year-old man in Italy also fueled quick decisions, although none of the deaths have been fully investigated to determine whether there is any link to the shots they received.

A blood clot is a thickened, gelatinous blob of blood that can block circulation. Clots form in response to injuries and can also be caused by many illnesses, including cancer and genetic disorders, certain drugs and prolonged sitting or bed rest. Clots that form in the legs sometimes break off and travel to the lungs or brain, where they can be deadly. (Representative Image)

Vaccines have not been shown to cause blood clots, said Daniel Salmon, director of the Institute for Vaccine Safety at Johns Hopkins University. Blood clots are common in the general population, and health authorities suspect that the cases reported in vaccine recipients are most likely coincidental and not related to the vaccination.

Dr. David Wohl, director of the vaccine clinic at the University of North Carolina, said he had seen no evidence that any of the COVID vaccines had caused blood clots, also called thrombosis, in the large clinical trials that led to their authorization. But Wohl also noted, "There are differences between trials and real life." The most extensive safety results from the real-world rollout of AstraZeneca's vaccine come from Britain, where 9.7 million doses of the vaccine had been given out through last month. Britain's data found that at least some clotting conditions, while extremely rare, were equally prevalent for people vaccinated with AstraZeneca's vaccine compared to those who got Pfizer's product. But abnormally low platelet levels were more common among people who got AstraZeneca's vaccine.