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XE, the new strain of Covid against which we must not lower our guard

The coronavirus “has not stopped evolving,” warns Dr. Rafael Cantón, head of Microbiology at the Ramón y Cajal hospital in Madrid, and although “we are in a valley, we must not lower our guard” in the face of new variants such as XE, which is growing in the United Kingdom but not yet more serious. “The need to extend the fourth dose towards the end of the year, beyond the most vulnerable groups that are already taking it, cannot be ruled out,” and it would be “recommended that this new dose be from a more up-to-date vaccine,” he explains.

Of the XE variant, in Spain “some very sporadic cases have already been detected” in virus sequencing carried out at the end of March, “without any dispersion having occurred at the moment. We will have to wait, making an effort in sequencing and not lower our guard,” he explains to Efe. XE is a recombination of omicron strains BA.1 and BA.2 and is rapidly increasing in the UK, with cases also occurring in Canada, Australia and Japan.

“In Spain we can be calm because if there are more variants, they will be found. A representative number is sequenced and, by lowering the positives, as the sequencing capacity of the laboratories remains the same, the possibility of finding new variants increases proportionally” . Just because it’s “highly transmissible doesn’t mean it’s more severe clinically,” although there are as yet no reports of risk assessments of XE by British epidemiologists who excel in this area.

“We have a lot to learn from them. They have precise and highly developed surveillance systems. They make very early reports, with a scientific method and very good models,” he asserts. The Ramón y Cajal, Gregorio Marañón and La Paz hospitals are sentinel laboratories in Madrid. The sequencing data is sent to the National Center for Microbiology, which, in turn, sends it to the European Center for Control of Infectious Diseases (ECDC).

“Spain is ready,” he insists, but we must “stay vigilant, not relax.” And although the sequencing is random, now “more is being monitored at the tip of the iceberg, the cases that enter and go to the ICUs, than at the base of the pyramid. But at the base we have a sentinel surveillance system just like with the flu”. Regarding a possible “flu” of the covid in 2023, she assures that the experts do not like the word flu.

“The coronavirus has proven to be an aggressive virus, whose aggressiveness has varied over time, but we cannot predict what will happen in the future. It is true that vigilance can lead to flu, but this does not mean that the importance of illness”.

Fourth dose by the end of the year

This specialist does not rule out that the fourth dose should be extended towards the end of the year, “in the last quarter”, to more sections of the population than the vulnerable groups that are currently being immunized.

“The logical and recommended thing is that this fourth dose be of a more up-to-date vaccine, as is already the case with the flu, which is being updated successively, and even with other pathogens such as the pneumococcal vaccine,” he details.

In viruses, the variants “are much more dynamic than those of other microorganisms and make a much more agile modification necessary.” Some variants have less vaccine protection but “the infrastructure of the pharmaceutical companies is prepared to modify the vaccines if necessary”. Regarding the convenience of rotating vaccines so that this fourth dose allows a more global immunization, Dr. Cantón considers that “there are no reliable studies that say this.”

In fact, it was said that the rotation would make the immunization more complete, being “more general on the one hand and more specific on the other. So that the immune system receives different insults, so to speak, and its reaction is better” . But doing this type of study “is complex, we will see it published later,” according to this specialist for whom the end of the pandemic “is difficult to predict.”

The combination of mutations in the structure of the protein S (‘spike’) of the virus can mean that “the models that are established are not fulfilled”, although he trusts that the vaccine coverage will maintain the “protective effect”.

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