AstraZeneca vaccine: 79% effective and without rare blood clots in US test

Enlargement / Filters of the AstraZeneca COVID-19 vaccine can be seen at the opening of a vaccination center in Cyprus, on March 22, 2021.

Exceeding expectations, the two-dose AstraZeneca COVID-19 vaccine proved to be highly effective against symptomatic and severe disease in a new late trial conducted differently in the US. The company said it was now seeking emergency use permission from the Food and Drug Administration. However, vaccination may still be questionable.

The Phase III trial conducted in the U.S., Peru, and Chile found that the vaccine was 79 percent effective in preventing symbolic disease, the company reported early Monday. Previous test results suggest efficiency could be as low as 62 percent.

In the new 32,449-person trial, two-thirds of participants were given the vaccine and the other third were given a placebo. There were five cases of severe disease in the trial, all in the placebo group. None of the vaccination participants required hospitalization.

In particular, the company found no increased risk of bleeding events or cases of a rare, life-threatening blood event, known as CVST, among those who received the vaccine.

Blood clots

A small number of adverse blood events in people who have been vaccinated have raised widespread concern in Europe and other countries, where the vaccine is already authorized for use. In the weeks or so, more than a dozen countries – Germany, France, Italy and Spain – suspended the release of the AstraZeneca vaccine, which was developed in collaboration with Oxford University.

Among more than 20 million people who have already been vaccinated in the European Union and the United Kingdom, at least 18 cases have been reported of CVST (sinus venous thrombosis), in which a clot prevents blood from clotting. drains from the brain, leading to stroke. There were at least seven other cases of people developing blood clots in several blood vessels, a condition known as diffuse intravascular coagulation, or DIC. Nine of the CVST and DIC cases died.

Last week, the World Health Organization and the European Medicines Agency conducted an independent review of all the data and eventually persuaded countries to re-vaccinate start quickly. Both groups concluded that risks of severe infection and death from COVID-19 outweighed the extremely rare risk of bleeding events.

The WHO and the EMA noted that among the millions of people who received the vaccine, reports of bleeding events – which are common in general – were lower than would be expected in the general population. They were also unable to determine whether the vaccine caused CVST or DIC issues. But they could not deny the case, especially since the majority of cases were in people under 55.

In the EMA study, the groups noted:

According to pre-COVID figures, it was estimated that less than 1 case of DIC reported by March 16 among people under 50 would be expected within 14 days of receiving the vaccine, but 5 cases were reported . Similarly, on average 1.35 cases of CVST would be expected among this age group but at the same completion date there were 12. A similar imbalance was seen in the older population with the vaccine.

Difficult questions

The new test results did not detect any issues with CVST, but—if so there is a real connection – this is not surprising based on the very low frequency of these events. The trial data included safety data for just about 21,500 vaccines, but the small number of out-of-trial cases occurred among up to 20 million vaccinated people.

While there is a real chance that the cases are just statistically significant flu, some researchers acknowledge that the vaccine may – rarely – come up with an autoimmune response. explain the ailments, and have suggested possible treatments. Other researchers have also noted that vaccination is not linked to unbelievable bleeding events; COVID-19 itself is linked to bleeding disorders, and research suggests that the spike protein SARS-CoV-2 can trigger immune responses that can lead to clotting.

But it will take a lot more data to make the connection firmly (if there is one), as well as to find out how the vaccine stimulates such a response, and who might be taking it. effect. Like the other authorized COVID-19 vaccines, the AstraZeneca vaccine delivers to cells only the genetic code for the SARS-CoV-2 spike protein, which can train immune responses to target the virus. The vaccine does this by using a non-packaged adenovirus, similar to the Johnson & Johnson vaccine, the latest vaccine authorized by the FDA.

For now, the FDA will be watching as it reviews the data and decides whether to implement EUA. The group seems to be looking favorably on the efficacy and safety data of the new test and seeing the vaccine as another useful tool in the fight against SARS-CoV-2. However, gaining public support may be a greater barrier to the vaccine moving forward. In addition to the concerns about bleeding, the vaccine has gone through a fallout after a clumsy development – from test stops that are widely publicized due to unexplained illnesses and traumatic errors. some participants, to recent data suggesting that it may be useless as opposed to moderate to moderate. COVID-19 caused by version B.1.351.

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