What about the side effects of AstraZeneca and Johnson & Johnson vaccines?

PARIS.- After the AstraZeneca vaccine began to be linked to a atypical blood clot condition, Johnson & Johnson’s, based on the same technology, is the target of the same suspicions.

In an “excess of caution”, The United States Food and Drug Administration (FDA) today recommended the suspension of the application of Johnson & Johnson’s vaccine while investigating unusual thrombosis events in the inoculated individuals.

Several European countries restricted the dose of AstraZeneca use in the elderly last week due to thrombotic events they observed in young people. This vaccine is not yet licensed in the United States. What do we know so far?

What does “pause” the application mean?

During clinical trials and after vaccines become widespread, experts keep track of any medical problems reported by a person who has been vaccinated. If an unusual event is repeatedly reported, regulators may decide to suspend or stop testing of the vaccine for further investigation.

Breaks are common, and research generally shows that medical issues turn out to be coincidences.. If the investigation reveals that the vaccine is risky, the regulatory authority will prepare guidelines on who can and cannot receive the serum.

What has been observed?

In both cases, suspicion arose after the detection of several cases of thrombosis in vaccinated persons.

These are not simple thromboses, like phlebitis, but very rare conditions. First, because of their location: they affect the veins of the brain and to a lesser extent the abdomen, said the European Medicines Agency (EMA) on April 7 of AstraZeneca.

The Johnson & Johnson vaccine also saw “cerebral venous sinus thrombosis,” US health officials, the FDA and the CDC said on Tuesday.

These conditions occur with a drop in the level of blood platelets, so that at the same time as the blood clots the patient may suffer from bleeding. The EMA first acknowledged on April 7 that these problems could be caused by the AstraZeneca vaccine.

In exchange, this link has not yet been formally established with the Johnson & Johnson vaccine, licensed but not yet administered in Europe under the name Janssen. In the United States, his post was suspended Tuesday pending a scientific response.

And what is it due to?

These problems could be related to the technique of the two vaccines “viral vectors”. This is based on taking another virus as a carrier, which is modified so that it carries genetic information in the body capable of fighting Covid-19.

Both use an adenovirus, a very common type of virus. AstraZeneca is a chimpanzee adenovirus and Johnson & Johnson is human.

“Everything indicates that it is due to the adenovirus vector,” he explained on Twitter. Mathieu Molimard, French specialist in pharmacology, recalling that this type of problem does not occur with the Pfizer / BioNTech and Moderna vaccines, which use the messenger RNA technique.

For now, it is not known whether these pathologies are also recorded with another vaccine using an adenovirus, the Russian Sputnik. This is allowed in about 60 countries but not in the European Union or the United States.

What are the mechanisms?

Several elements indicate a excessive immune reaction caused by these vaccines. In a study published online on March 28, researchers from Germany and Austria drew a comparison with another known mechanism.

The phenomenon “clinically resembles heparin-induced thrombocytopenia (HIT),” said the team of scientists led by Andreas Greinacher of the University of Greifswald.

HIT is an unusual, severe and abnormal immune reaction triggered in some patients by the anticoagulant, heparin. That’s a “plausible explanation,” the EMA assessed on April 7, calling for further studies.

What’s the risk?

This is the main question. According to figures from the EMA, as of April 4, 222 cases of atypical thrombosis had been detected after 34 million injections of AstraZeneca. in the 30 countries of the European Economic Area (EU, Iceland, Norway, Liechtenstein) and in the United Kingdom. With a balance of 18 dead until March 22.

The thromboses occurred “during the two weeks following the vaccination”, according to the EMA.

In the case of Johnson & Johnson, US authorities have recorded six cases, including one death, among more than 6.8 million doses administered, and symptoms appeared between 6 and 13 days after the injection. But, as with all medications, the key is to weigh the risks against the benefits.

“The vaccine’s overall benefits in preventing Covid-19 outweigh the risks of side effects,” the EMA said of AstraZeneca.

What are the risk factors?

For the time being, most AstraZeneca cases involved “women under 60”, according to the EMA. The six cases detected in the United States with Johnson & Johnson were women between the ages of 18 and 48. But it is too early to draw any conclusions. So far, “we haven’t identified any specific risk factors,” said AstraZeneca’s EMA.

After the first wave of suspensions, in mid-March, some countries decided to stop using the vaccine below a certain age: 30 in the UK, 55 in France, Belgium and Canada; 60 in Germany and the Netherlands and 65 in Sweden and Finland.

“We don’t have just one vaccine, we have several. So it seems logical to me to reserve AstraZeneca for the elderly, ”Sandra Ciesek, virologist at Goethe University in Frankfurt, told Science magazine.

British authorities have released a chart showing that Covid-19 poses a six times higher health risk than the vaccine in 20-29 year olds. But in the 60-69 age group, the risk is 600 times greater. Norway and Denmark have chosen to completely stop the use of the AstraZeneca vaccine.

Can be treated?

German and Norwegian doctors have treated patients with anticoagulant drugs to try to stop the formation of thrombi, and with intravenous immunoglobulin, to try to eliminate the antibodies that are causing this strange problem.

German researchers stress that treatment should start as soon as possible because if we are not treated in time, the condition could get worse.

AFP agency and The New York Times newspaper

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