With input from Dr Monica Vasudev

1551:      The University of Oxford has halted the administration of COVID-19 vaccine that they have developed with AstraZeneca, in a small U.K. study to test it in children and teenagers, until more information is available about rare blood clot issues in adults who have received it.

The pediatric trial being done by Oxford was started in mid-February to test the vaccine in over 200 individuals aged 6 to 17 years. No safety issues have been observed in the trial itself. However, concerns about rare clotting events in adults have prompted regulatory reviews in the U.K. and Europe to look into any potential link with the vaccine.

This halt comes as a setback for the Oxford-AstraZeneca vaccine, which has been questioned about its efficacy and potential side effects even as millions of doses have been administered following safety issues in over 70 countries.

1552: The European Medicines Agency (EMA) has again stated that the AstraZeneca COVID-19 vaccine is safe and effective and the benefits in protecting against COVID-19 outweigh any possible risk. However, it says that a link between rare cases of thrombosis with thrombocytopenia and the vaccine cannot be ruled out.

The EMA announcement emphasizing the safety of the vaccine came at a press conference which, confusingly, took place at the same time when a UK press conference was held at which it was recommended that the AstraZeneca vaccine should not be used in those below 30 years of age if an alternative vaccine was available.

Speaking at the EMA press conference on April 7, Emer Cooke, executive director at the EMA, stated that their review suggested that the AstraZeneca vaccine was not associated with any increased risk of overall thromboembolic events or blood clots, but a small number of very rare but serious clotting disorders have been noted, which led to a more focused review.

The EMA advises that patients should seek medical care if they develop any of the following symptoms: shortness of breath; chest pain; swelling in leg; persistent abdominal pain; neurological symptoms, including severe and persistent headaches or blurred vision; or tiny blood spots under the skin other than the site of injection.

There have been some very rare cases of unusual events of thrombosis and thrombocytopenia and bleeding.

In some cases, tiny clots develop in several blood vessels during the initial 7-14 days following vaccination. This is termed as disseminated intravascular coagulation (DIC). In some other cases, clots have developed in blood vessels that drain blood from the brain (cerebral venous sinus thrombosis (CVST)). These conditions are tied to low platelet count. 

At the EMA press conference, Sabine Straus, MD, chair of the EMAs Pharmacovigilance Risk Assessment Committee (PRAC), stressed that as of April 6, 7 cases of DIC and 18 cases of CVST had been reported from among the 20 million people who had received the AstraZeneca vaccine.

Of the CVST cases, 7 were reported from Germany, 3 from Italy, 2 from Norway, 1 from Spain, 3 from the UK, and 2 from India.

Meanwhile, at the UK press conference, it was reported that there had been 79 reports of blood clotting cases with low platelets from the UK following the use of the AstraZeneca vaccine; 44 of these were categorized as CVST with thrombocytopenia.

Anthony Harnden, deputy chair of the UKs Joint Committee on Vaccination and Immunization (JCVI), said that if someone has received a first dose of the AstraZeneca vaccine, they should be given the second dose. He further stated that they have not seen any case of thrombosis with thrombocytopenia after the second dose thus far, but agreed that they havent administered as many second doses yet. He recommend against mixing vaccines at present. 

(The Washington Post; Medscape)

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA