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The Omicron variant of the coronavirus can partially evade the protection from Pfizer Inc and partner BioNTech’s COVID-19 vaccine, the research head of a laboratory at Africa Health Research Institute in South Africa said on Tuesday.

Alex Sigal, a professor at the Africa Health Research Institute, said on Twitter there was “a very large drop” in neutralization of the Omicron variant relative to an earlier strain of COVID. The lab tested blood from 12 people who had been vaccinated with the Pfizer/BioNTech vaccine, according to a manuscript posted on the website for his lab. The preliminary data in the manuscript has not yet been peer reviewed.

Blood from five out of six people who had been vaccinated as well as previously infected with COVID-19 still neutralized the Omicron variant, the manuscript said.

According to the manuscript, they observed a 41-fold decline in levels of neutralizing antibodies against the Omicron variant.

The Omicron COVID-19 variant has sparked global concern and prompted new travel restrictions. Here’s everything you need to know

Sigal said on Twitter that figure is likely to be adjusted after his lab does more experiments.

While neutralizing antibodies are an indicator of the body’s immune response, scientists believe other kinds of cells such as B-cells and T-cells also are stimulated by the vaccines and help protect against the effects of coronavirus.

The Omicron variant, first detected in southern Africa last month, has triggered alarms globally of another surge in infections, with more than two dozen countries from Japan to the United States reporting cases.

The World Health Organization on Nov. 26 classified it as a “variant of concern” but said there was no evidence to support the need for new vaccines specifically designed to tackle the Omicron variant with its many mutations.

There is not significant data yet on how vaccines from Moderna, Johnson & Johnson and other drugmakers hold up against the new variant. All the manufacturers, including Pfizer, are expected to release their own data within weeks.

Top U.S. infectious disease expert Dr. Anthony Fauci said on Tuesday that preliminary evidence indicates that the Omicron variant of the coronavirus likely has a higher degree of transmissibility but is less severe.

He said the United States was doing its own tests to determine the protectiveness of the current vaccines against the variant and expects results sometime next week.

Umer Raffat, an analyst for Evercore ISI, cautioned against reading too much into a single study, noting that there has been significant variability in measuring declines in antibody levels in previous lab studies.

“Let’s wait for additional studies to draw a mosaic,” he said.

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