are the symptoms more severe? How protected are the vaccinated? – Corriere.it

from Laura Cuppini

What do we know about the new variant of Covid, the Omicron: according to experts, it is likely that the shield offered by vaccines against serious forms of disease remains high anyway

Omicron’s Italian “patient zero” had already received two doses at the time of the infection in South Africa. Should we fear that the new variant will escape vaccines?

It will take a few weeks to answer this question, but the companies that produce mRna vaccines are already working on a preparation specifically directed against Omicron that could be ready – according to Pfizer – in “a hundred days”. The possibility that the strain “holes” the protection offered by current vaccines is however considered remote by experts. “It is more likely that the virus partially escapes the immune defense, as already happened in the Delta infection in which the effectiveness of vaccines has dropped compared to previous variants, but the defense against serious disease has remained high – he explains. Sergio Abrignani, full professor of Immunology at the State University of Milan and director of the National Institute of Molecular Genetics “Romeo and Enrica Invernizzi” -. In the case of Omicron, a further decrease in protection against infection is possible, but still a good defense against severe disease ».

The new strain has 32 mutations in the Spike – is it worrying?

It is not certain that all mutations are “negative”, or that they make the virus more transmissible or pathogenic. Omicron has some characteristics common to the Beta and Gamma variants (those considered more “dangerous”), but to understand the ability of current vaccines to protect against infection and disease, further data on the protective effect of antibodies and T lymphocytes are needed. “Neutralizing antibodies inhibit infection by preventing the virus from entering cells, while T lymphocytes are also needed to protect against the disease, which kill already infected cells – clarifies Abrignani -: neutralizing antibodies mostly recognize the very region mutated of the Spike that binds to human cells, the T lymphocytes instead affect regions of the virus that have no function of interaction with human cells and that have remained well preserved compared to previous variants ».

Is the third dose of the vaccine protective, even if not “perfect” for Omicron?

Yes, because it strengthens the immune response which, as mentioned, also affects areas of the virus unchanged compared to the original strain, that of Wuhan. A possible Omicron spike-specific vaccine – such as those announced by Pfizer and Moderna – could be used for the fourth dose.

Is it theoretically possible that Omicron causes more severe symptoms?

Yes, even if the first data from South Africa would indicate that, at least in the vaccinated, a mild disease occurs. However, it must be considered that the country’s population is young, with an average life expectancy of only 58 years. In the coming days we will see what happens when Omicron spreads to areas where there are many elderly and frail people. «The questions we will have to answer are three – says Sergio Abrignani -: is it more widespread than the dominant variant (Delta), as it would seem from the very first information? Does it induce a more severe disease? Are vaccinated from the Wuhan strain still protected – at least in part – from severe disease, mild to moderate symptoms and infection? Giorgio Palù, president of the Italian drug agency, said guest a Half an hour more that “there are no scientific reasons for an alarm. We suspect that Omicron is very contagious – he added -, but a virus with all these mutations could also prove to be less virulent ».

Do we risk new lockdowns?

The weapon we have at the moment is the vaccine, it is important that everyone continue, complete or possibly begin the vaccination cycle of three doses (two for the recovered). There was a first effect of Omicron, also thanks to the introduction of the super green pass: the administration of the first doses increased by 40% compared to last week.

Is it possible that the Omicron variant developed, as hypothesized by geneticist François Balloux of University College London, in an immunocompromised individual, perhaps because of untreated HIV / AIDS?

It is probable, given that the prevalence of HIV / AIDS is very high in South Africa. “It is not surprising that a new variant may have appeared for the first time in the organism of an individual with few immune defenses, given that in that situation Sars-CoV-2 can replicate for several months (thus having many opportunities to accumulate mutations) before be eliminated – Abrignani points out -. Conversely, vaccines generally do not promote mutations, as has been erroneously heard in recent months. The presence of the strong vaccine immune response resolves the infection in a few weeks, reducing the number of replications of the virus “.

November 29, 2021 (change November 29, 2021 | 08:30)

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