Is Omicron Evading Immunity?

"All [U.K.] systems and teams are on standby to run the analysis, but my sense is we are still a long way from that number [the requirement for an accurate analysis to have at least 200 Omicron-infected individuals for an effective study]."

"So we depend on South Africa [to provide an earlier analysis given their large and growing number of Omicron-infected population]."

Meaghan Kall, lead epidemiologist in COVID-19, U.K. Health Security Agency

"Viruses do not inevitably evolve to become less virulent over time. If this has happened with Omicron -- and it's too early to tell whether it has -- it would be a matter of good fortune."

"Many viruses do not attenuate [reduce in force] over time. Influenza remains far worse than a common cold. Measles, even more so. Smallpox, worse yet."

"This is unlikely to be a factor for COVID, [the virus becoming less lethal over time] where death occurs weeks after the transmission causes."

"To paraphrase and generalize [the study], virulence is often not so much a matter of evolutionary fine-tuning as a matter of s--- happens."

Professor Carl Bergstrom, theoretical and evolutionary biologist, University of Washington, Seattle 

Medics at an infectious-disease unit in South Africa, where a new strain of COVID is spreading quickly.  Credit: Alet Pretorius/Gallo Images/Getty

The world sits on tenterhooks, awaiting word on whether the latest mutated SARS-CoV-2 variant Omicron, is more virulent than its predecessors. Virulence denotes the capacity of a pathogen to inflict harm on any it infects. It is Omicron's potential for damage at a steeper level than the currently most infectious strain, Delta, that grips the painful imagination of health experts and the governments they represent, to fully understand the new threat before them, presaging their population-protective responses. 

Should the investigation into the properties of the new 'variant of interest' turn out to be relatively mild, the current restrictions imposed speedily on news of its presence and spread, are certain to be revoked. Should the variant present as more transmissible, more deadly, the world has good reason to cringe in distress. All the more so should it prove it can bypass the protection the current vaccines are noted for, as a lifeline to the future.

To arrive at a fairly definitive answer to the questions revolving around Omicron, scientists require "several hundred" confirmed Omicron cases that they could track from the time of infection to its finish.  This is a process whose timing and revelations thereof lie in the spike region of the virus now spreading in numbers throughout southern Africa and beyond. According to early reports from South Africa, hospital cases rose sharply in the province most affected, quadrupling from 134 to 580 in two weeks' time.

And on the other hand, news from primary care doctors in South Africa speak of symptoms in Omicron patients being unusual, but mild. Since it is yet early days that assessment may be altered as the virus spreads into older age groups. At present, however, nothing appears to be particularly frightening as far as symptoms and early outcomes are concerned. With hard data missing for now, evolutionary biologists have been explaining the type of evolutionary pressures facing the virus, and how they may impact humanity.

First off, they have cautioned there is no reason to believe that gains in the virus transmissibility equates to a lessening of its virulence. Professor Bergstrom, as an example, warns against the thought that viruses evolve to become less virulent "to keep their hosts alive and thereby transmit more". The Alpha and Delta variants are both more transmissible and more dangerous than was the original virus that they overtook. In the process, the natural reproduction rate of the virus grew from a median estimate of 2.79 in 2020 to 5.08 with today's Delta.

 

Pedestrians wearing face masks against the coronavirus walk along Regent Street in London, Nov. 30, 2021.   (AP Photo/Alastair Grant)

 

And as such, risks of ending up in hospital in the U.K and dying has commensurately increased with the evolved virus. Alpha and Delta, on the other hand emerged when immunization achieved through natural infection aftermath and also vaccination was at a lower state than at present. High immunization, including vaccinations on the increase worldwide has resulted in the viruses' selective pressures altering the way it evolves.   

Given the number of mutations that have evolved in Omicron's spike it seems the virus has focused on evading human immunity. What has also been realized by investigators is the randomness exhibited by the virus. Viral evolution can be "short sighted", according to an academic paper dating back to 1994, and highlighted by Dr.Bergstrom, with pathogens becoming far more dangerous with no advantage gained to the pathogen as a result. Bacterial meningitis, he points out, a classic example.

 

 

A number of countries are tightening travel restrictions over fears about the new COVID-19 variant called Omicron. Image: REUTERS/Loren Elliott

"Viruses kill host cells and damage host tissues when replicating [within the human body]. Thus, a pathogen that is better at replicating within hosts, spreads more virions in the environment, and hence transmits better and generally tends to be intrinsically more virulent."

"A virus replicating in the upper airways could be highly transmissible yet fairly benign to its host. [But] a viral strain replicating within organs [lungs, kidneys] is expected to cause extensive damage."

"If we're unlucky, Omicron's ability to [re]infect immunized hosts doesn't significantly impact its high replication rate [-and the damage it causes to host tissues]."

"If we're a bit lucky, its ability to [re]infect immunized hosts does reduce its replication rate, and hence would be expected to cause, on average, less severe symptoms, send fewer people into hospital and reduce fatality rates."

Francois Balloux, director, UCL Genetics Institute, professor of computational biology, University College London