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Astrazeneca vaccine debateWhat is known about effectiveness and side effects

The corona vaccine from the British-Swedish group Astrazeneca has come under criticism, especially because of the rare serious side effects. In Germany, since a decision by the Bund-Laender Round of May 6th, all adults can be vaccinated with the vaccine regardless of their prioritization. In addition, the time interval between the second vaccination may be shortened at the doctor's discretion. Until the decision was made, an interval of twelve weeks was required between the first and second dose.

In terms of application, the vaccine has several advantages compared to vaccines from other manufacturers: It does not have to be laboriously cooled, but can be kept in the refrigerator and can therefore be inoculated more easily. It is also cheaper.

Despite these advantages, the EU has not yet extended the contract with Astrazeneca. The current contract runs until June and developments will continue to be monitored, said EU Industry Commissioner Thierry Breton on May 9th. Breton also emphasized: "This is a good vaccine". However, there are reservations about the vaccine not only in Germany but also in other EU countries.

Is a quick second dose recommended?

In the future, in consultation with the person being vaccinated, according to the federal-state resolution, the doctor should also be free to set the interval for a second Astrazeneca vaccination between four and twelve weeks. "Many people prefer to have the second vaccination earlier, also with a view to the summer - with Astrazeneca that is also possible within the approval period," said Federal Health Minister Jens Spahn on the WDR. Astrazeneca-vaccinated people would then have to wait less long until the corona restrictions were removed.

However, Astrazeneca vaccinees would have the disadvantage of possibly less effectiveness in the case of an earlier second syringe. The Vaccination Commission recommends an interval of twelve weeks between the first and second dose for the preparation. The background to this are observations that the longer distance leads to better effectiveness. According to a report by the European approval authority EMA, the effectiveness of two vaccinations every four to eight weeks is 50.4 percent. With twelve weeks or more, it increases to 72.1 percent to 82.4 percent.

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Astrazeneca and Sinus Vein Thrombosis

In mid-March 2021, there were first reports of a possible connection between vaccination with Astrazeneca and sinus vein thrombosis occurring in the near future. As of April 15, 59 cases of sinus vein thrombosis after vaccination with the AstraZeneca vaccine Vaxzevria had been reported to the Paul Ehrlich Institute. Twelve victims died. The European Medicines Agency (EMA) reports a total of 142 cases for the EU.

Vaccine-induced thrombocytopenia

There is an explanatory approach for at least some of the cases. The symptoms you experience remind doctors of rare serious side effects associated with heparin, a blood thinner that is supposed to prevent blood clots. The body's own blood platelets, the thrombocytes, play an essential role. These usually adhere to the tiny wounds that are constantly forming in the veins. This creates tiny clots that close this bleeding. The so-called platelet factor PF4, a protein that the blood platelets produce, plays an important role in blood clotting. During the healing process, the body then breaks down these mini-thromboses again.

However, during treatment with heparin, the immune system rarely makes antibodies against the platelets. This activates these blood platelets and also an enzyme for blood clotting and then leads to a tendency to thrombosis, the so-called heparin-induced thrombocytopenia.

The same mechanism could occur with Astrazeneca vaccination. This is what studies by a research team led by coagulation specialist Andreas Greinacher from the Greifswald University Hospital suggest. Greinacher and his team also found antibodies against platelets in eight female and one male vaccinated. Because they suspect the same mechanism behind it, they speak of vaccine-induced thrombocytopenia.

How does thrombocytopenia occur?

In simplified terms, the mechanism that leads to thrombocytopenia can be described as follows: Small clots form everywhere in the body, to which platelets adhere. That is why the number of blood platelets drops sharply. This in turn can lead to major bleeding because the mini-wounds can no longer be closed. If larger clots develop, for example in the brain, sinus vein thrombosis can develop. In the worst case, the resulting blood congestion can press on regions of the brain or constrict them. The result is symptoms such as persistent headache, visual disturbances and other neurological deficits. The entire mechanism can ultimately be life-threatening, as has been shown.

In a new work, the research team from Greifswald has now tried to trace the path from vaccination to the formation of these antibodies. Various elements of the innate immune response play a role here. The side effect only occurs when several of these controls fail in the body, so it is extremely rare. Because many control mechanisms have to be bypassed, there is no one simple test that could predict the risk. It is also unclear whether the same processes also take place with the vaccine from Johnson & Johnson, which also relies on cold viruses.

The question is also how high the risk of thrombosis is after a second vaccination, says Christine Falk, head of the Institute for Transplant Immunology at the Hannover Medical School. So far there is no study that investigates this. In England, over five million people were vaccinated with the second dose. "If that were a common occurrence, it would have been noticed." Nevertheless, the question arises of how to minimize the risk of a second vaccination. The Standing Vaccination Commission recommends a different vaccine for the second vaccination.

The work of the research team from Greifswald now also provides information that AstraZeneca may be able to take into account when adapting the vaccine to new corona variants.

Why are women more affected?

It is still unclear why the majority of sinus vein thrombosis after vaccinations occurred in women between the ages of 20 and 55 years. However, even without vaccinations, such sinus vein thrombosis occurs more frequently in women in these age groups than in other population groups. In 25 to 35 percent of cases, the cause is unknown.

First therapeutic approaches

There are already therapeutic approaches based on experience with comparable reactions to heparin. Because they are well known, diagnosis is relatively easy - if the treating medical staff thinks of thrombocytopenia. This can then be treated with a blood thinner, but in this case not with heparin. Because that could exacerbate the thrombocytopenia. In addition, the administration of antibody preparations in order to quasi-dilute the dangerous antibodies against PF4. This is already recommended by the Society for Thrombosis and Hemostasis Research.

The Paul Ehrlich Institute called for careful attention to the side effects:

"People who 'feel increasingly unwell more than four days after the vaccination - for example with severe and persistent headaches or punctiform skin bleeding' - should seek medical treatment immediately."

What other side effects have you seen so far?

Allergic reaction

According to the EMA on March 12, there are 41 reports of possible cases of anaphylactic reactions after vaccination with the Astrazeneca vaccine among five million vaccinees in Great Britain. are serious, potentially life-threatening immediate reactions. The EMA considers a connection to vaccination to be likely, at least in some cases.

At the same time, the EMA pointed out that severe allergic reactions are a known rare side effect even with vaccinations against other diseases. The Astrazeneca package insert already recommends that patients should at least remain after vaccination 15 minutes under observation should remain in order to be able to treat possible allergic reactions immediately.

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Other side effects

Compared to other vaccines, several people who had been vaccinated, mostly hospital employees, reported some significant vaccine reactions. Fever, headache, chills, fatigue, and flu-like symptoms are common.

According to the RKI and the Paul Ehrlich Institute, these are the usual vaccine side effects that can also occur with other vaccines. The manufacturer Astrazeneca sees no cause for concern and reports "mild to moderate" side effects, which were also expected.

"The most disturbing were probably the attacks of fever and chills," said DLF science editor Christian Floto. Fever is not at all exciting during a vaccination, especially in younger people - they have the more active immune system. It is due to the type of vaccine that reactions turn out differently than, for example, with the mRNa vaccine from Biontech / Pfizer.

In a publication on the Astrazeneca clinical phase 2 study, it is said that around 85 percent of subjects under 55 years of age had at least one vaccination reaction after the first corona vaccination, such as headache and fever, mostly mild to moderate - a relatively high number , says science journalist Arndt Reuning in the Dlf. For comparison: According to vaccine expert Helen Chu from the University of Washington in Seattle, this value is only a good 35 percent for a comparable age group for a flu vaccine.

Astrazeneca for people over 60 years

The German Federal Government's Standing Vaccination Commission (STIKO) updated its recommendation for vaccination with the vaccine on March 30th. The background was the rare cases of thrombosis in cerebral veins in connection with vaccination. Therefore only people should nowfrom 60 yearsbe vaccinated with it. The federal states followed this recommendation.

The Berlin clinics Vivantes and Charité had previously stopped all vaccinations of their employees under the age of 55 with the vaccine until further notice. The heads of five of the six university clinics in North Rhine-Westphalia had also spoken out in favor of a temporary Astrazeneca vaccination freeze. The risk of further deaths is too high, according to a joint letter to the federal and state health ministers.

The STIKO had only recommended the Astrazeneca vaccine for people over 65 years of age on March 4, 2021. The basis for this was the analysis and evaluation of more recent study data, which also demonstrate good effectiveness for the older age groups. The STIKO initially advised against vaccinating people over 65 with the Astrazeneca vaccine because there was too little data available for this age group at the time. A new large-scale study presented in March 2021 confirmed the high effectiveness also for over 65-year-olds. For those over 65 years of age, the value is included85 percent even higher than with younger people.

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EMA unreservedly recommends Astrazeneca

The European Medicines Agency EMA has unreservedly recommended the use of Astrazeneca for all age groups over 16 (April 7th, 2021). The benefits should be rated higher than the risks. However, blood clots should be listed as rare side effects.

In an interview with the Italian newspaper "Il Messaggero", the head of the EMA vaccination department, Marco Cavaleri, said that according to his own assessment there was an as yet undetermined connection between incidents with blood clots in the brain and the Astrazeneca vaccinations. "In my opinion, we can now say that there is a connection with the vaccine. We do not yet know what triggers this reaction," said Cavaleri.

In mid-March 2021, the EMA had stated that there was no evidence that the vaccinations had caused the thrombosis incidents. Since that was not excluded, however, investigations were ongoing.

Does Astrazeneca work sufficiently against the coronavirus?

Yes. The vaccine from Astrazeneca prevents death and severe courses from the disease Covid-19 and probably also protects against long-term consequences - just like the other vaccines approved in Germany. So it protects against ending up in the intensive care unit, being ventilated and dying. However, a study in which only 2,000 people took part found that the vaccine was less effective for the South African coronavirus variant. The Astrazeneca vaccine is said to offer only "minimal protection" against mild and moderate disease courses.

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Nevertheless, virologist Christian Drosten considers fundamental concerns about the Astrazeneca vaccine to be unfounded. In the NDR podcast "The Coronavirus Update" he said that he thought the British version in particular was relevant in this country. The Astrazeneca vaccine is also effective against these, according to a study by Oxford University.

The statement by the chairman of the World Medical Association, Frank Ulrich Montgomery, that he understands medical staff who do not want to be vaccinated with the Astrazeneca vaccine is what the SPD health expert Karl Lauterbach calls "completely irresponsible" on Twitter. He himself will be vaccinated with the Astrazeneca vaccine.

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The benefits of the vaccination significantly exceed the risks, especially for the elderly, said SPD health expert Karl Lauterbach in the Dlf.

What does 76 percent effectiveness mean?

In the case of vaccines, this expresses the percentage of how much smaller the risk of disease is in people who have been vaccinated compared to those who have not been vaccinated. So it doesn't mean that out of ten people who are vaccinated, only seven are protected. This misunderstanding is dangerous because it contributes to uncertainty, comments Martin Mair in the Dlf.

The manufacturers determine the value according to their respective studies. One group is given the vaccine, the other a placebo. Now it is determined how many people in each group get Covid-19. If more cases of the disease are counted in the placebo group than in the vaccinated group, the vaccine apparently protects and is therefore effective. Now it is calculated how much lower the disease risk was in the vaccinated group.

At Biontech, people in the vaccination group had a 95 reduced risk of contracting Covid-19. "Getting sick" does not mean getting seriously ill; a cough is also one of the symptoms of an infection. The American infectiologist Lawrence Corey pointed this out: "Do you want a vaccine that will protect you from coughing or do you want a vaccine that will keep you from dying?"

New study confirms high effectiveness of Astrazeneca

The 76 percent that Astrazeneca currently gives for its vaccine (values ​​of 60 to 70 percent were previously mentioned) are even a good value for a vaccine. Although it is below the effectiveness of the vaccines from Biontech and Moderna. But many flu vaccines are only 50 percent effective in the elderly and still save hundreds of thousands every year.

At the end of March 2021, a new large-scale study with 32,500 test subjects in the USA, Chile and Peru once again confirmed the high effectiveness of the vaccine. According to the scientists involved, the vaccine protects against infection with SarsCoV-2 with an effectiveness of 79 percent and 100 percent against severe disease. Around 20 percent of the participants were 65 years of age or older. Shortly after the study was published, there were doubts in the United States about the timeliness of the data. Astrazeneca announced the cooperation with the corresponding control body and then corrected the effectiveness slightly downwards 76 percent

How do the vaccine responses at Astrazeneca differ from the other corona vaccines?

The Paul Ehrlich Institute, which is responsible for reporting side effects, received more suspected cases of the Astrazeneca vaccine than of the other two vaccines approved in Germany.Science journalist Arndt Reuning emphasized in the Dlf that when comparing different products one also had to pay attention to which groups of people had been vaccinated: The Astrazeneca vaccine was initially not approved in Germany for people aged 65 and over, so younger people were vaccinated with it. Their immune system reacts more strongly than in older people.

Reporting could also play a role, according to Reuning: Because the media reported more critically about the vector vaccine, more reports could have been received for Astrazeneca than for the mRNA vaccines. However, there are also differences in the profile of the vaccine reactions with the vaccines, said Reuning.

From the clinical studies it is known: At Astrazeneca the reactions to the first vaccination appointment are more violent than the second. That could also have contributed to this perception that Astrazeneca causes stronger side effects. With the corona vaccine from Biontech / Pfizer, for example, it is exactly the opposite: most vaccination reactions there are stronger at the second appointment than at the first.

Second vaccination after Astrazeneca

Under 60-year-olds who have received a first corona vaccination with the Astrazeneca vaccine should now receive a different agent for the second. This emerges from a revised recommendation of the Standing Vaccination Commission from April 1st. There is still no scientific knowledge about vaccinations with different means. Infectiologist Marylyn Addo has no concerns about combining different vaccines.

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Infectiologist Marylyn Addo thinks this makes sense: Although the data situation is still thin, there is a lot to suggest that this approach is safe, Addo said in the Dlf.

Source: above, Joachim Budde, Christian Floto, RKI, Federal Ministry of Health, Astrazeneca, RWI