Certainties and unknowns about the omicron variant to start the year


Just over a month ago, the omicron variant broke into the current pandemic. On November 26, the WHO classified it as 'worrying', in part because it had "more than thirty mutations in the spicule gene, in addition to numerous mutations in other regions of the genome", many of which had already been related "to an increase in transmissibility or with a certain degree of escape to the immune response ", is explained in the latest whitepaper of the Ministry of Health.


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Researchers around the world set out to study it against the clock. After weeks of speculation, the first conclusive works confirm omicron's ability to infect beyond the shield of vaccines. In contrast, vaccines do appear to remain effective against severe disease, although data on this issue remain preliminary.

Two doses of vaccines do not prevent infection

On December 23, the magazine Nature published five team studies in U.S, Europe (France, Swiss), South Africa Y China, all of them reviewed by independent researchers. Although with variations, the common purpose of these studies was to analyze whether the antibodies of people vaccinated, or those who had overcome COVID-19, stop an infection or reinfection by omicron. All detected a significant, even total, loss of this ability.

Now, the experts insist - in statements to the Vaccine Media Hub- in that antibodies are one of the body's first lines of defense against COVID but not the only one; that they lose the ability to slow the progression of the infection does not mean that the vaccines do not work.

The third dose could make a shield

Two of the studies published in Nature found that the loss of effectiveness of the antibodies "is less after a third dose of the vaccine," the authors write. job led by Davide Corti, of Humabs Biomed SA, a Vir Biotechnology company.

Preliminary data generated by the United Kingdom shows that the effectiveness of the Pfizer vaccine in preventing infection would be 70-75% after the third dose

Also the team led by Olivier Schwartz, from the Pasteur Institute (France), find that "omicron escapes most of the monoclonal antibodies and to a great extent also the antibodies generated by vaccines, [pero] is still neutralized by the antibodies generated by the booster dose (booster dose) ".

The preliminary data generated by the United Kingdom Health Safety Agency (UKHSA) show that the effectiveness of the Pfizer vaccine in preventing infection would be 70-75% after the third dose.

Vaccines could prevent serious disease

"I think we already know that the vaccines maintain responses against the variant and will surely be sufficient to maintain their objective of avoiding serious illness and significantly reducing hospitalization," he declared to the Vaccine Media Hub Manuel Juan, head of the Immunology service at the Hospital Clínic de Barcelona, ​​on December 10.

He was referring to the fact that, although the antibodies do not neutralize omicron, everything indicates that cellular immunity, slower to activate, will continue to be equally effective. For Juan, "the response of the T cells will be at least partially conserved. (…) It is expected that the omicron variant will have a spectrum of protection similar to the other variants, since this protection is not so much quantitative but qualitative, explained by the immunological memory that will exist ".

Although the antibodies do not neutralize omicron, everything indicates that cellular immunity, slower to activate, will continue to be equally effective

It is an opinion shared, among others, by Vicente Más, Researcher in the Laboratory of Viral Biology of the Carlos III Health Institute, who states: "According to the omicron sequence analysis, the response of the T cells should not be seen so seriously It is expected that the administered vaccines maintain an important level of efficacy to avoid serious infections, not so much in reducing the level of infections and reinfections ".

Cellular immunity is more difficult to measure than antibodies. Even so, preliminary work public facts by the UK Public Health agency and cited by the WHO point out that cellular immunity maintains its effectiveness. Studies also point in the same direction South Africa Y USA.

It has spread rapidly through Spain

The latest Health data they collect until December 19: indeed, as in many countries, "in Spain a rapid growth has also been detected in recent weeks" of omicron. Random samplings by specific PCR detected between December 13 and 19, with data from 13 autonomous communities, omicron percentages between 3.1% in Andalusia, followed by Murcia with 3.7%; and 54.8% (Canary Islands and Madrid).

"There is a rapid replacement of the delta variant by omicron," the report said. "Given the speed with which this expansion is taking place, the delay in obtaining and communicating the results means that the values ​​reflected in the weeks included in the report may underestimate the intensity of the circulation of this variant at the present time" .

Estimates of how much more transmissible it is differ, but some suggest a rate two to three times greater than delta

Prevention measures still work

The mask, interpersonal distance, hand hygiene and ventilation "are effective for all variants", including omicron, insists Health.

Yes, it is more transmittable

This was suspected since the existence of omicron was detected, given its rapid expansion. The calculations on how much more transmissible they differ - it is not easy to measure it, many social factors also intervene - but some estimates suggest a rhythm between two and three times greater than delta. British researchers have calculated that with omicron it is three times as likely as with delta to infect a partner.

Is COVID-19 milder by omicron? We do not know

Much has been said, but the truth is that it is not easy to know. The apparent mildness of omicron infections could be due to the fact that the majority of those infected had previous immunity -by the vaccine or an infection-, such as explained two weeks ago Epidemiologist Maria Van Kerkhove, Technical Head of the Response to COVID-19 and of the Emerging Diseases and Zoonoses Unit at WHO.

In addition to vaccination, some studies published in recent days based on tests on animals and human tissues in the laboratory - with all the precautions that this implies - suggest that a possible lower severity of omicron infections could be due to their impact it focuses, above all, on the upper respiratory tract - nose, mouth and throat - and is more limited on the lungs or bronchi, as indicated by this recent information from the New York Times.

It was estimated that omicron would be 25% less severe than delta, but delta was already more severe than the original, so this would make omicron still more dangerous than the original SARS-CoV-2

A report published by Imperial College London he estimated that omicron would be about 25% less severe than delta. However, keep in mind that delta was already more severe than the original variant, so this would make omicron still more dangerous than the original SARS-CoV-2. Furthermore, experts fear that the higher transmission capacity will 'overcompensate' for this difference.

In any case, the latest Health report states: "Data are still too scarce to determine the true impact of the omicron variant on the epidemiological characteristics of the infection, but preliminary studies point to greater transmissibility and greater immune escape. There is still a high level of uncertainty as to how much to possible changes in the severity of the cases ".

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