The number of rare blood clots cases among the million people in the UK who received the Oxford / AstraZeneca vaccine has risen to 168.
The UK Medicines Agency said the overall death rate was 19%, with 32 deaths as of April 14th.
That number has risen from 22 deaths by April 5.
The Medicines and Health Products Regulatory Authority (MHRA) said that while the estimated incidence rate of cases has increased over time, the number of cases remains extremely low, given the millions of doses administered.
The regulator continues to believe that the benefits of the AstraZeneca vaccine continue to outweigh the risks for the vast majority of people.
The MHRA said in its latest weekly yellow card reporting summary that by April 14 it had received reports of 168 cases of serious thromboembolic events (blood clots) with concomitant thrombocytopenia (low platelet count) in people who had the AstraZeneca sting had .
That’s an increase from 100 case reports by April 5th.
Of the 168 cases in the most recent summary, 77 cases reported cerebral sinus thrombosis (CVST or blood clot in the brain) and 91 cases had other serious thromboembolic events with concomitant thrombocytopenia.
The mean age of CVST cases is 47 years, while for the other major thromboembolic events the mean age is 55 years.
In total, rare blood clots developed in 93 women and 75 men between the ages of 18 and 93 years.
One case was reported after a second dose of the vaccine, the regulator said.
The estimated number of first doses of the AstraZeneca vaccine dispensed in the UK by April 14 was 21.2 million, making an overall incidence of 7.9 per million doses, according to the MHRA.
This corresponds to an incidence rate of 4.9 per million doses through April 5.
Professor Adam Finn, Professor of Pediatrics at Bristol University and a member of the Joint Committee on Vaccination and Immunization (JCVI), said it was “already clear that it (thrombotic thrombocytopenic syndrome) will remain a very rare occurrence”.
He said reports of more cases were “as expected”.
Prof. Finn said, “The public and doctors across the country are now very aware of this syndrome. Cases are reported reliably and quickly, but there are also cases that occurred before and are now detected and reported.
“MHRA uses a very well-defined case definition to ensure consistency. In other words, they make sure that the cases reported are really that syndrome and not something else.
“This can take some time, and although there are uncertainties, unconfirmed cases are classified as possible or likely.
“I would expect the actual number of cases per million vaccine doses to become clear pretty soon once these reports stabilize, but it is already clear that this will remain a very rare occurrence.
“There remains an urgent need to understand the mechanism underlying these cases, to monitor and optimize rapid diagnosis and treatment, and, if possible, to identify risk factors, all of which could improve outcomes and enable cases to be prevented.”