‘Stealth Version’ of Omicron Detected, Evasion of Vaccine Protection in Laboratory Experiments

Slowly, some facts and figures have started to emerge regarding the latest variant of the coronavirus -- the Omicron. Scientists across the world have been delving deep into discovering the reality of the hypotheses, the common and much hyped perceptions. Only a few days back we got to know about the possibility of re-infection by the Omicron variant.

The World Health Organization (WHO) has cautioned against any complacencies at this juncture, which “will cost lives”, said WHO director in a press briefing in Geneva on December 8. The consistent picture of rapid transmission across the world caused by the new variant has been highlighted in the briefing.

Despite the South African data of increased risk of re-infection, there is a need of more data to come from other parts of the world. the Omicron variant may also cause milder disease in comparison to that by Delta, but no definitive statement can be passed as of now.

“New data are emerging every day, but scientists need time to complete studies and interpret the results. We must be careful about drawing firm conclusions until we have a more complete picture,” commented WHO Director-general, Tedros Ghebreyesus, speaking to journalists in Geneva.

Now, two other important aspects have been brought to light; one is the discovery of a ‘stealth version’ of the variant which is harder to track by the usual PCR (Polymerase Chain Reaction) technique and the other important aspect is the laboratory findings which hint towards possible evasion of vaccine protection by Omicron.

Omicron May Weaken Vaccine Protection:

It may be true, as suggested by first laboratory studies, that Omicron can evade some protections provided by the Covid vaccines. However, the preliminary studies by teams in South Africa, Germany, Sweden and Pfizer-BioNTech collaboration also hint that the protections by the currently available vaccines may not be totally wiped out. The researchers also advocate for booster doses as means of improving immunity. Supporting it, virologist Penny Moore of the University of Witwatersrand, Johannesburg, commented saying, “We’re likely to see reduced effectiveness of vaccines against preventing infection. I think it’s a strong argument to get boosters out there.” Penny Moore is one of the co-authors of a paper that studied the evasion of vaccine protection by Omicron.

The results came from four separate studies with all suggesting that Omicron may blunt the potency of the neutralising antibodies, more in comparison to other variant of SARS-CoV-2, the coronavirus driving the COVID-19 pandemic. The neutralising antibodies circulate in the blood when a person get vaccinated or have had a previous bout of infection by the coronavirus. These antibodies, a class of protein molecules in the immune system, can block or neutralise viral particles.

The scientists of the studies broadly used two types of approaches in their laboratory studies: one uses the particles of the virus itself isolated from infected people, and the other approach uses pseudovirus particles, which are genetically modified forms of other viruses (for example the HIV virus) that has the spike protein similar to the coronavirus.

One study led by Alex Sigal of the African Health Research Institute, Durban, South Africa, reported to have found serum from 12 people who were immunised by the Pfizer-BioNTech vaccine to be 40 times less potent against the Omicron variant. The serum is the portion of blood that has the antibodies.

This study got similar results as found in other two studies. One is from the Pfizer-BioNTech study which was reported on December 8 in a press release and the other one is as reported by virologist Sandra Ciesek at Goethe University, Frankfurt, Germany.

The fourth study was led by virologist Daniel Sheward and Ben Murrel of the Karolinska Institute, Sweden. They found reductions in the level of neutralising antibodies against Omicron in two different groups of participants—one group consisted of 17 healthcare workers who were previously infected and the other having 17 Swedish blood donors.

Murrel commented on the findings of the studies that the conclusions of the studies are similar and the neutralising antibodies cannot fully knockout Omicron. He further said—“The magnitude is still a little up for question.”

The results of the preliminary experiments suggest that vaccine protections are significantly impacted by Omicron, however, it remains to be found the degree of the impact.

Stealth Version of Omicron:

The Guardian reported on December 7 about scientists identifying a ‘Stealth Version’ of the Omicron. It was found that the stealth version cannot be distinguished from other variants when the common PCR test is conducted.

Public health officials, scientists across the world are using the RT-PCR test as a proxy to quickly identify the Omicron variant. The actual analysis of the genetics of any variant can be done suing genome sequencing technique, which is more time consuming. However, the RT-PCR test, used as a proxy, provides some rapid detection pathway.

Omicron has over 50 mutations (random changes in the genes), some of which include missing of some amino acids in the spike protein. The amino acids are the building blocks of any protein and are symbolically designated by alphabets. The amino acids are tied up in a variety of combinations and form a protein. the Omicron has one of the amino acids missing; it is the S-gene target. This S-gene target missing can be detected by RT-PCR and is used as the proxy. Importantly, the previous variants of Alpha could also be identified with the same proxy technique.

The ‘Stealth Version’ does not have the S-gene target missing and thus, cannot be tracked with the RT-PCR technique. The Stealth Version has been spotted in samples collected in South Africa, Australia and Canada in recent times.

Regarding the spread pattern of the stealth version, researchers are still not conclusive; it cannot be said whether it will follow the same pattern as the usual Omicron variant.