How does the AstraZeneca vaccine work?

The Ovford-AstraZeneca vaccine is a vaccine based on the viral vector, that is, it uses a virus (of the chimpanzee), harmless to humans, which acts as a spacecraft to transport the genetic code of the virus proteins against which the production of antibodies is to be triggered in human cells. The target is the Spike protein. This virus cannot replicate itself in the human body or make you sick. It can be kept at 2-8 degrees and therefore very handy. It costs less than three euros.

How effective on the adult population and the elderly?

A ballet of numbers has been unleashed on the efficacy data in the last few days. The latest (and hopefully definitive on this trial) were announced on Thursday 25 March. They report that the prevention of Covid is 76% (with a confidence interval ranging from 68% to 82%). In adults aged equal to and above 65 years, vaccine efficacy was 85% (with a confidence interval from 58% to 95%). The drug showed a100% effectiveness in preventing serious diseases, hospitalization and deaths. There were eight cases of severe Covid observed in the primary analysis all in the placebo group. On March 22, AstraZeneca had to release in a press release the preliminary results of this clinical trial carried out in the United States, Chile and Peru on 32,449 volunteers, claiming that the vaccine effective at 79% (without to indicate the confidence interval) reporting the ‘absence of serious side effects (not even the thrombosis due to which the European governments had decided a four-day stop waiting for an EMA ruling). In the night the National Institute of Allergy and Infectious Diseases, the governing body Antony Fauci, said the National Institutes of Health (NIH) data and safety monitoring committee had notified government agencies (and AstraZeneca) that they were concerned about the information the drug company released Monday morning as incomplete and obsolete, thus urging the pharmaceutical company to submit more up-to-date data. AstrAzeneca is committed to doing this within 48 hours and thus comes the latest updated efficacy data: 76% (instead of the previously announced 79%). The result, however, appears to be more robust than a previous pooled analysis of clinical trials in the UK, South Africa and Brazil which had shown efficacy of around 62%.


Where used?

At the end of March, the AstraZeneca vaccine received authorization in over 80 countries: The first was the United Kingdom in December then followed by the European Union, Canada, India, Argentina, Dominican Republic, El Salvador, Mexico, Morocco. The World Health Organization has made the vaccine available even to low-income countries. Between the UK and the European Union, 17 million people have received the AstraZeneca vaccine (as of March 14).

What are the ideal timing between the first and second dose?

The optimal timing for the double dose is not yet very clear. In the two large studies conducted in the UK and the US the second dose was administered within 28 days of each other. In the first results released in November, a subset of participants who had accidentally received less vaccine in the first dose were less likely to develop Covid-19. It was later clarified that the increased protection did not derive from a dosing error, but from the longer period between the first and second dose thanks to a study published in Lancet which indicated 82% efficacy when the second dose is administered during the twelfth week. At the moment in Italy, also given the shortage of vaccines, the booster with AstraZeneca is expected 3 months after the first administration. WHO recommends an interval of 8 to 12 weeks.

Does it work against variants?

A preliminary analysis in a UK study of the AstraZeneca vaccine found that it provides a similar level of protection against variant B.1.1.7, first detected in the UK. The situation with the South African variant, on the other hand, is more complicated. A small study of about 2,000 adults under the age of 65 found that it did not protect against mild and moderate Covid-19 with that variant. South Africa has suspended the dissemination of the AstraZeneca vaccine, but the WHO still recommends its use for protection against serious disease. AstraZeneca has announced testing new variant vaccines.

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Vaccine and thrombosis: how did the blood clot story end?

Following a series of reports of serious adverse events of the thromboembolic type and some deaths that have affected people vaccinated with AstaZeneca, many European countries, starting from Thursday 11 March, have decided to temporarily suspend vaccinations as a precaution: Italy has suspended them on March 15. The push for suspension in Europe arose after an evaluation by the German institute for vaccines Paul Ehrlich Institute (homologous authority to our Higher Institute of Health). Experts have reported a noticeable increase in a very rare special form of cerebral vein thrombosis (sinus vein thrombosis linked to occlusion of the brain vein) in connection with a lack of platelets (thrombocytopenia) and bleeding in conjunction with AstraZeneca vaccinations . The German health minister confirmed that there were 7 cases of cerebral venous thrombosis reported after vaccination (of which 3 died) out of 1.6 million vaccinations in Germany, 6 women and 1 man all between 20 and 50 years old. The March 18 the European Medicines Agency called to investigate the new adverse effects reported and concluded that the AstraZeneca vaccine is effective and safe. The EMA has clarified that it has started to see a small number of cases of rare and unusual, but very serious, blood clotting disorders, particularly affecting young women and cannot yet definitively rule out a link between these cases and the vaccine. Out of nearly 20 million vaccinated people, 7 cases of blood clots in multiple blood vessels and 18 cases of cerebral venous thrombosis have been reported. In the latest data from the trial carried out in the United States, however, no safety concerns were reported with regard to blood clots and no increased risk of thrombosis was found. Ema recommended that he come the package leaflet updated also reporting these rare events. The signs to look out for are: Shortness of breath, pain in the chest or stomach, swelling or cold in an arm or leg, severe or worsening headache or blurred vision after vaccination, persistent bleeding, multiple small bruises. After the green light of the EMA, vaccinations resumed in Italy and in most countries in Europe.

March 28, 2021 (change March 29, 2021 | 19:21)

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