Five countries are studying the possibility of combining COVID-19 vaccines, but the evidence for its benefits is still inconclusive

Five countries are considering whether to swap the doses of the 12 COVID-19 vaccines that have been authorized for emergency use and are being applied worldwide. They evaluate this strategy as an alternative for situations where there are delays in dose deliveries or concerns about safety issues, among other reasons. But there is still not enough evidence on its benefits. A prestigious researcher from the University of Oxford has warned that it is not yet known what the best combination between vaccines would be and that there would be a risk of reducing the level of tolerance. when receiving the second dose of a product that was developed on a different platform.

“For now, the general recommendation is not to trade COVID-19 vaccines. Because there is not enough data yet. The possibility is under study ”, he commented. Infobae Florencia Cahn, President of the Argentine Vaccination Society (SAVE).

Canada is one of five countries studying the so-called “interchangeability” of vaccines. A few weeks ago, the health authorities of this country had informed that people who had received the vaccine that AstraZeneca marketed could be offered a second dose of another vaccine.

The Canadian announcement followed the increased incidence of rare blood clots linked to the first doses produced by the Anglo-Swedish drug maker. However, The scientific group which advises the World Health Organization (WHO) on vaccination argues that the benefits of the clinical trial of the vaccine of AstraZeneca They far outweigh the risks, based on the updated recommendations you just posted.

To find out if sharing vaccines is safe and effective, in Canada, a clinical trial will be conducted with different vaccines for the first and second doses in 1,300 adult participants. The study will be conducted in collaboration with the COVID-19 Immunity Working Group, the Vaccine Surveillance Reference Group, the Canadian Immunization Research Network and Dalhousie University. This work will examine the effect of different doses and the time interval between their application and how long their protection would last.

As, In South Korea, the health authority announced on May 20 that it would conduct a COVID-19 vaccine combination trial, with dosages of AstraZeneca products with those developed by Pfizer and other companies. In China, the dose combination of the COVID-19 vaccine developed by CanSino Biologics and a unit of Chongqing Zhifei Biological Products is under study. There, the health authority recognized that it is studying the possibility of combining the doses of the vaccine developed with different technologies to increase its effectiveness.

The Finnish Institute of Health and Welfare would give a messenger RNA vaccine as a second dose to those under 65 who have already received AstraZeneca. This decision was also recommended by the main French health advisory body for those under 55. A similar decision assesses Norway. In the United States, at the moment, they support the exchange between the doses of the two authorized messenger RNA vaccines.

Spain’s Health Minister Carolina Darias said on May 19 that people under the age of 60 who received a first dose of the AstraZeneca vaccine would be allowed to receive a second dose of the AstraZeneca or AstraZeneca vaccine. Pfizer / BioNTech. The Spanish Bioethics Committee has recommended that the option be given to 1.5 million essential workers who are still awaiting the second dose. They could receive the Pfizer / BioNTech vaccine with informed consent.

In Spain, one of the vaccine exchange studies is underway called “Combivac”. The study in Spain is in phase 2. The participants are people under the age of 60 who had already received a first and only dose of the AstraZeneca vaccine. Participants had to be at least in the eighth week after the first dose.

As stated in a press release from Spanish researchers, “the first results indicate that this heterologous vaccination schedule is highly immunogenic and does not present various post-vaccination reactogenicity problems. to those already reported in the homologous use (alone) of these same vaccines ”. This would mean that the immune system response is greatly improved after the second dose of the Pfizer / BioNTech vaccine.

However, studies have yet to provide conclusive evidence. “What we still don’t know is what the best combination is. Which vaccine is best to inject first. This is what the new studies must answer to, to optimize the combination, ”said Andrew Pollard, director of the Vaccine Group at the University of Oxford, England. There, they are conducting another study, the ComCOV, which will provide answers in a month or two.

The first results of the study in England revealed that people who received the Pfizer vaccine followed by a dose of AstraZeneca, or vice versa, they were more likely to have mild or moderate common symptoms after vaccination than if they received two of the same type. This higher frequency of side effects could lower the tolerance level of the combination, although according to Dr. Pollard.

Also in England, there will be another trial in June that will include seven vaccines to assess whether they need a third booster. In this study, doses of the vaccine from the company Novavax will be used, indicating that the combination of doses will be evaluated.

“The preliminary results of the exchange speak of a good response in terms of efficiency, but they are still ongoing. Messenger RNA vaccines would have better prospects for this exchange, ”said Liliana Vázquez, infectious disease specialist and member of the Argentine Society of Infectology (SADI). “It is possible,” said Dr Vázquez to the question Infobae– that the coronavirus infection circulates to a lesser extent in the future as does the flu. Maybe in the future the exchange of different vaccines will be used. It is also possible that a COVID-19 vaccine booster is needed and the swapping of different doses could play a role. “

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