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According to the new recommendations, Germany can vaccinate its citizens who have already received the first dose of AstraZeneca with other vaccines. These are to be products of the companies Pfizer / BioNTech or Moderny. This approach was surprising, but it turns out to be nothing new. Research on combining different types of vaccines has already been carried out, for example, in the case of the Ebola virus. In the UK, the different preparations can be combined from January, and the AstraZeneca-Pfizer pair tests will end this month.
- In Germany, 31 cases of thrombosis were reported until March 31 following AstraZeneca vaccine, and 9 had died
- The Standing Committee on Vaccinations issued a recommendation that instead of the second dose of AstraZeneki vaccine, Pfizer / BioNTech or Moderny preparations should be administered
- Is it safe and effective to mix different vaccines?
- You can find more such stories on the TvoiLokony home page
COVID-19 Vaccines. Second dose of vaccine with a different type of preparation
Since the end of March, there has been a recommendation in Germany that only people over 60 years of age should be vaccinated with AstraZeneca.
– The recommendation was issued by the Standing Committee on Immunization (Stiko), which is part of the Robert Koch Institute – says Dr. Krzysztof Pujdak, a specialist in internal medicine and cardiology at the Herford Clinic. – It includes epidemiologists, virologists, microbiologists and even pediatricians. It is an advisory body whose decisions are not legally or ordinarily regulated, but as far as I know, all the Länder have complied with.
Dr. Pujdak claims that the Stiko reaction took place after numerous reports that especially in young women vaccinated with the British preparation, cerebral vein thrombosis occurred more often than it would appear from statistics.
– Vaccinations with AstraZeneca were discontinued on March 15, the risk was reassessed, it was found that it is increased, but at the same time it does not exceed the benefits of vaccination – says Dr. Pujdak. – They were entered in the leaflet and doctors were advised to inform patients that this could happen. They were vaccinated further, but it turned out that by March 31, there had been 31 cases of thrombosis and nine people had died, including seven women.
Dr. Pujdak recalls the loud death of a 32-year-old psychologist working in a rehabilitation clinic 10 km from his place of residence. It was precisely the thrombosis of the cerebral veins. The accident caused a storm.
It should be added that the assumptions about a direct relationship between AstraZeneca vaccination and thromboembolic complications have not been proven.
– If, for example, an 80-year-old dies after vaccination with this preparation, it is often not known what was the direct cause of death – explains Dr. Pujdak. – It is said that e.g. comorbid disease or age. Such a death is also not of interest to the media. The death of a healthy 30-year-old is different. It seems to me that quite a few different complications have not been registered and cannot be swept under the rug.
Meanwhile, the German health minister is to discuss the recommendation of the vaccination committee with the health ministers of the federal states.
– So far, the interval between successive doses has been extended – adds Dr. Pujdak. – Demand for the AstraZeneki vaccine is still high. Interestingly, until two months ago, those who interpreted clinical trials claimed that it does not work as well in people over 60 as it does in younger people. Then the question is, is this a wise decision? Older people are at the highest risk of covid complications, so maybe the profit and loss calculation shows that it’s not that bad after all.
The Standing Immunization Committee made another recommendation – that instead of the second dose of AstraZeneca vaccine, Pfizer / BioNTech or Moderny should be given within 12 weeks of the first vaccination. The reasoning quoted by Deutsche Welle was as follows: “protection from AstraZeneca begins to wane after 12 weeks”.
The Pfizer / BioNTech and Moderna vaccines are preparations based on completely different technologies – mRNA – however, the chairman of the committee said that animal studies showed that when two different preparations were administered, the immune response is not weaker. On what was his claim based?
Mixing Doses of Different COVID-19 Vaccines
The UK revised its immunization guidelines as early as January this year. The new recommendations were: “If a second dose of a given vaccine is not available, patients can get a different one”.
At that time, there was as yet no evidence that mixing two coronavirus vaccines was safe and effective.
In February, researchers at the University of Oxford began a study in which volunteers were given a dose of Pfizer-BioNTech, followed by a dose of AstraZeneca, and vice versa. As new vaccines are approved, they will test more combinations. According to them, mixing dose types not only patches holes in supplies, some suspect that different types of vaccine may work better than two doses of one.
“I think we are on the threshold of some interesting discoveries,” said Dr. Adam Wheatley, an immunologist at the University of Melbourne, Australia. The concept of vaccine mixing – sometimes called heterologous basal stimulation – is not new. For decades, scientists have been studying this type of approach with the hope of finding effective combinations against influenza, HIV and Ebola viruses.
Two different vaccines have been shown to work well in mice, but conducting clinical trials of a combination vaccine in humans is a difficult task, because just one company developing two types of vaccine takes twice as much work.
One of the successes of combining various preparations is the search for a vaccine against the Ebola virus. The researchers inserted the gene for a protein found on the surface of this virus into another, harmless virus. After inoculation, the harmless virus got into cells that read the instructions from the Ebola gene and produced the Ebola surface protein. The immune system encountered this protein and made antibodies. This type of vaccine, called viral vector vaccine, carries a high risk – recipients may develop immunity to the viral vector after the first dose. After taking the second dose, their immune systems could destroy the viral vector before it delivered its payload. To avoid this potential hazard, different viruses were used in each dose. This would make the viral vectors of the second dose just as new to the immune system as those of the first.
For example, scientists at the Gamaley Institute in 2017 created a vaccine against the Ebola virus, the first dose of which contained a virus called adenovirus, and the second dose of another virus, vesicular stomatitis.
Last year, they used a similar strategy to create a vaccine against the coronavirus. The first dose contained the same adenovirus as in the Ebola vaccine (Ad5) and the second dose contained a different human adenovirus, Ad26. Researchers introduced the coronavirus spike protein gene into both viruses. Studies have shown that the vaccine, known as Sputnik V, offers strong protection against COVID-19 and is 91,6 percent effective.
The Gamaley Institute recently joined forces with AstraZeneca. The AstraZeneki vaccine consists of two doses of chimpanzee adenovirus (ChAdOx1) and is 76% effective. The Gamaley and AstraZeneka teams want to see if their vaccines are working together. In clinical trials, volunteers will receive a dose of AstraZeneki and a second dose of Sputnik V.
Dr. Jakob Cramer, head of development at CEPI, a vaccine research organization, says it isn’t just vectored vaccines that will benefit from combining different doses.
Dr. Wheatley tested protein-based vaccines in mice. For the first dose, his team injected the animals with complete protein. In the second dose, only the spike protein. It turned out that the mixture worked better than the same two doses. Some vaccines, especially protein-based vaccines, are good at making antibodies. Others, vector ones, train immune cells better.
After the UK was criticized for suggesting that vaccines could be mixed, researchers in Oxford decided to test the idea. They recruited 830 volunteers for a study called Com-Cov. They tested two approved vaccines – the adenovirus-based AstraZeneca and a formulation from Pfizer-BioNTech.
One group of volunteers will receive an injection of Pfizer-BioNTech and then AstraZeneca, while the other will receive them in the reverse order. The remaining volunteers receive the standard two-dose version of the vaccines.
Later this month, the Oxford team will take blood from the test subjects to check for antibodies and immune cells. It then remains to be seen whether the combination of the different preparations produces an immune response that is as strong as two doses of each of the approved vaccines.
There are 13 approved COVID-19 vaccines worldwide, and 67 more are in clinical trials. As the number of vaccines increases, so will the number of combinations in which they can be used.
See also:
- Thrombosis. How is it related to COVID-19 and the AstraZeneki vaccine? The doctor explains
- Expert: There is a link between AstraZeneki vaccine and blood clots
- UK United Kingdom: Seven people who have been vaccinated with AstraZeneka die from blood clots; BBC: two issues raise suspicions
- When do COVID-19 vaccines start to work, and how do you check it? [WE EXPLAIN]
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