The White House adviser on the health crisis spoke in a telephone interview of the first known elements and the uncertainties surrounding the new variant which is spreading in the world: its transmissibility, the immune response of vaccinated and former patients and the severity of infections.

Omicron is "clearly highly transmissible", possibly more than Delta, which is almost hegemonic in the world, according to Dr Fauci.

The results of laboratory experiments on the effectiveness of antibodies from current vaccines should be known "in the next few days to within a week," he said.

Global epidemiological data also shows a higher rate of re-infections with Omicron and that the variant is probably more immune to vaccine immunity.

But "it is almost certain that he is no more serious than Delta," said Anthony Fauci.

"There are some signs that it may even be even less serious," he added.

Studies currently being carried out in South Africa, where the variant was detected in November, show that the ratio between contaminations and the number of hospitalizations "seems lower than for Delta", he explained.

Two scenarios

The data from South Africa should not be overinterpreted, he warned, however, the population of this country having the particularity of being very young and less at risk of being hospitalized, while the severe forms may take several weeks to develop.

"I think it will take another two weeks at least in South Africa, then when we have more infections in the rest of the world, it might take us longer to see the real level of severity", Dr Fauci stressed. .

As it stands, a more transmissible virus but which does not cause a severe form or an increase in hospitalizations would be "the most favorable scenario", he explained.

"The worst-case scenario would be to have a virus not only more easily transmitted but which causes severe forms of the disease and leads to another wave of infections which is not necessarily alleviated by the vaccine or previous contaminations," the scientist warned.

“I don't think the worst-case scenario will happen, but you never know,” he said.

The Omicron variant is now present in at least 38 countries.

Even if it is not linked to any death for the moment, scientists are worried about the unprecedented number of its mutations, including about thirty in the spike protein, the key to entering the virus into the body.

Disinformation

Its origin is still unknown, but there are two theories, according to Dr Fauci.

It may have developed in an immunocompromised patient, such as someone with HIV who did not fight off the virus quickly enough.

Or it can be passed from human to animal, then back after mutating, in a "reverse zoonosis" case.

To fight against its spread, Anthony Fauci advocates caution, especially when traveling, and wearing a mask indoors if we do not know the vaccination status of other people present.

Those who are eligible for the third dose of the vaccine should also receive it as soon as possible.

Studies, especially in Israel, show that the booster dose dramatically increases the antibody level and the intensity of the immune response, the doctor said.

But it is still too early to know whether this response is sustainable enough or whether it will be necessary to consider other vaccinations, he stressed.

In the United States, 60% of the population has been fully vaccinated since Tuesday, but much remains to be done, according to Dr Fauci.

The 80-year-old scientist, who has become the face of the fight against Covid-19, denounced the disinformation that is slowing down the vaccination campaign, especially in states controlled by the Republicans.

"There are 60 million people eligible for vaccination who are not, and in most cases for ideological reasons, it is unfortunate," he regretted.

"We should have a homogeneous response in terms of public health," he concluded.

© 2021 AFP