Omicron: Who's at risk?

With the Omicron variant of the coronavirus spreading through multiple countries, many have been reassured by statements made by doctors dealing with a widespread outbreak in South Africa, indicating that the strain seems much milder than previous dominant variants such as Delta.

However, in comments made to UK members of Parliament this week, Dr. Paul Burton, chief medical officer at Moderna, struck a warning note.

“I do not think Omicron is a milder, less severe version of the current virus,” he told the Parliamentary Committee on Science and Technology, as quoted by The Guardian.

“The idea it will push Delta out of the way and take over may occur in the future, but I think in the coming months these two viruses are going to co-exist, and Omicron, which I would maintain is actually a severe disease, will now infect people on a background of very, very strong Delta pressure.

“It will also lead to a situation where individuals will become co-infected … which gives the opportunity for this virus to further evolve and mutate which is a concerning and worrying situation,” he added.

“We certainly don’t have to panic as we have many, many tools at our disposal, and we’ve learnt so much about this virus over the last two years, and we can continue to fight it, but I think Omicron poses a real threat,” he warned. “While the mortality rate we are seeing right now is mercifully lower, I think as a disease it is a very fit virus and it’s severe.”

The question is, however, “severe” for whom? Is everyone equally susceptible, or are there risk factors? And the news coming out of South Africa, for those who are fully vaccinated, isn’t encouraging.

(Consider also that the first sequenced cases of Omicron were detected in fully vaccinated people – people who had received not just two doses but also a booster shot.)

According to vaccine expert Shabir Mahdi of the University of the Witwatersrand, who has, according to The Guardian, led vaccine trials in South Africa, the reason why those infected with Omicron in South Africa are experiencing mostly mild symptoms is that many South Africans have lived through previous infections.

Mahdi was interviewed by the Global Health Crisis Coordination Center, and he chose to highlight the results of a recently completed seropositivity survey in South Africa which showed that around 72 percent of the population has recovered from a COVID infection at some point in the past.

Although Omicron appears to be far more infectious than Delta, and also more able to evade antibody protection than previous predominant strains, he said, something other than antibody protection seems to be at work when one considers the low hospitalization and mortality rates he is seeing.

“In the South African, much of the immunity that currently exists is largely because of the prior infection that has taken place during the first three waves,” Mahdi said. “It tells us something is at play when the high force of infections with Omicron is not materializing in terms of severe disease and deaths in large numbers.”

What Mahdi posited as the “something at play” was the activity of T cells in protecting against more severe disease. In other words: Natural immunity is far superior to “vaccine-induced immunity,” something that numerous studies have demonstrated.