Health clarifies this week if a second dose of AstraZeneca will be used or if the vaccines will be combined


Publication: Monday, May 17, 2021 6:04 AM

It is expected that in the coming days, the Department of Health will resolve what will ultimately happen with the second dose of the AstraZeneca (or Vaxzevria, from the University of Oxford) vaccine. An issue that has put the government, scientists and health experts headlong, and which currently affects nearly two million Spaniards under the age of 60, including essential workers (teachers, police, military, civil servants, etc. prisons or health); people who have received the first dose of this formula, but are still unsure which one they will supplement the regimen for to be immune to the virus.

On the table, two options: that they receive a second injection of AstraZeneca or, on the contrary, one of Pfizer. The Public Health Commission will be the body responsible for making “the most appropriate decision” on how this process should be conducted. To determine a framework for action that can be extended to the entire territory, the regional directors of public health and health will take into account “observational studies” from the countries where both have been administered. In addition, they are awaiting the results of clinical trials dedicated to verifying the compatibility between the different vials.

Tests such as “Combivacs”, which is carried out by the Carlos III University. The aim of this work is to find out whether it is safe and effective to administer Pfizer, which uses the new “messenger RNA” technology, to those who have already received AstraZeneca at least eight weeks after the first inoculation. Although reaching the precise conclusions of the investigation – which is being carried out with only 600 people in hospitals in Madrid, Barcelona and Vizcaya – will take a few months, a spokesperson for Carlos III recently warned that this week the “preliminary results” which will be transferred to the ministry.

At present, the first reactogenicity data with a heterologous profile (adverse reactions presented by a patient immunized with different injections) from the trial that researchers at the University of Oxford (the same who developed AstraZeneca) have published in “ The Lancet ”, although this is not yet concluded. Based on tests performed on more than 800 volunteers, they have certified that patients who receive two different doses of the vaccine may experience more reactions – albeit mild and with common symptoms – compared to those given a full regimen with the same solution.

The combination of two vaccines “has been shown to be more effective than strictly identical injections in phase one and phase two studies in humans”

The problem with the Carlos III and Oxford trials is that they don’t have enough participants to get a representative sample with which to fully validate the results. It should not be forgotten that cases of thrombus occur in one in 100,000 people vaccinated. Likewise, it is not possible to get exact results on severe symptomatological reactions, nor to know exactly how this might affect other age groups, especially in young people. But that hasn’t stopped several organizations from already defending the controversial mix.

This is the case of the French Health Agency (HAS), which states that the use of different formulas “has been shown to be more effective than strictly identical injections in phase one and two studies in humans. “. Likewise, it recommends, because of the existence of “scientific justifications and encouraging data”, to use “one dose of one of the” messenger RNA “vaccines to replace the administration of the second in people under. 55 years old who received a first dose of Vaxzevria “in France. This” scientific justification “has led the French country to veto its implementation in all people under the age of 55, who are currently receiving a second dose of Moderna or Pfizer, and the same goes for Sweden and Finland.

Gaps between autonomous communities and countries

AstraZeneca (also Janssen or Sputnik) is a type of non-replicating viral vector. In other words, it uses a viral version of another virus (an adenovirus) modified in such a way as to trigger a reaction in the cells, giving them “ instructions ” to produce the S protein of the virus (spike), a minimal portion and no effect. Our body recognizes this protein as foreign and generates antibodies so that it does not grow and cause severe symptoms. Many scientists are studying whether this technique could be linked to the few cases of thrombi that have been recorded in some patients, which is why its use has been questioned or banned.

For their part, Pfizer and Moderna use the “Messenger RNA” procedure: instead of inserting an attenuated pathogen to create a response, instructions are introduced so that our body directly produces this protein which triggers the reaction of the immune system. It is believed that these differences could lead to arousing different parts of the immune system, increasing the immune response, and even prolonging the duration of immunity. In this specific case, it is believed that the application of this technology to techniques based on the introduction of adenoviruses could limit (even more) the possibility of thrombotic events.

This is underlined by organizations such as the aforementioned HAS, which consider that “there are many arguments in favor of this strategy”. “It has already been used in the development of certain vaccines (in particular against HIV)”, specifies the French agency, adding that those which “are mainly used in the development of anti-SARS-CoV-2 vaccination target the same antigen. protein S), which supports this strategy ”. Of course, not all organizations defend this position. Without going any further, the WHO and the Spanish Society of Immunology claim “patience” and “caution” in this process. They caution that this is a “hasty” and not yet proven solution, so in the absence of more data, they advise against it.

In a more direct position is the European Medicines Agency (EMA), which has been insisting on what it has been defending for weeks: “There is no indication that there are problems with a second dose (of AstraZeneca) . We continue to recommend that it be implemented. ” Also remember that the first injection already offers 80% protection. These discrepancies have had consequences, generating great doubts among countries – and among the territories that compose them – on the best way to immunize the population against COVID-19, to the point that it is moving in opposite directions.

France, Finland or Sweden have chosen to mix the vials, Denmark or Norway have decided to ban AstraZeneca completely and Germany or Italy inject this formula normally. Spain, for its part, continues to postpone its use pending the results of the Carlos III trial. But, as in the rest of Europe, the resolution of this conflict takes place in a context of great tension between the health and the autonomous communities, which insist that the ministry give “a rapid solution to the problem”. Currently Andalusia, Madrid, Catalonia, Murcia, Aragon and Euskadi are in favor of inoculating the second dose of AstraZeneca, defying the order of the central government.

Madrid proposes to put the second dose of AstraZeneca “to those who request it” if Health is not pronounced

The difference in criteria once again raised the tone to the maximum among political leaders, to the point that Isabel Díaz Ayuso threatened to start applying AstraZeneca on her own. His plan, supported by the Andalusian government, would work thanks to informed consent that was rejected by technicians of the Interterritorial Council. But far from resolving the confrontation with this answer, Madrid and other autonomies insisted: if there is no news these days, they will move on. It should be remembered that in our country the first dose of Vaxzevria was administered on February 8. According to the health calendar, the next one would have been on May 3. However, when the first cases of thrombi became known, it was decided to postpone the second ration for another four weeks (16 in total, instead of 12).

Vaccination data in Spain

Despite the problem caused by the Oxford formula, advances in immunization continue to contribute to the decline in all indicators. About 15 million people (36.3% of the population to be vaccinated) have already received a dose, while the complete schedule is almost 100% (98.2%) in those over 80 years old. Among people over 70 years old, 54.4% have the full regimen, while of people between 60 and 69 years old, only 7.2%, because they have to wait three months for the second dose because it is AstraZeneca serum. In total, in Spain there are already around seven million people with the two doses administered.

In addition, this Monday begins a key week of vaccination for 50 to 59 year olds. The Autonomous Communities will focus on their immunization from now on, while moving forward with the rest of the groups they have already started with. In addition, some territories are already targeting the following age groups: at the beginning of June, those under 49 will also begin to receive the first doses, or at least that is the intention of Andalusia, Asturias, Balearic Islands, Castile and León, Valencian Community, Madrid, Catalonia, Castile-La Mancha and Extremadura. In addition, the latter two want, by the end of June, to start with those under 39.

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