Will an omicron infection protect against delta and other strains?

The rapid rise of omicron has prompted a fair amount of wishful thinking. Stop us if you’ve heard some version of the following:

The answer, in each case, is a big, fat “not necessarily.”

While there could be some truth to these statements, infectious disease experts caution that for a variety of reasons, it remains a really bad idea simply to throw up your hands and stop taking precautions. Masks are still a good practice. Avoid crowded, poorly ventilated spaces. And above all, get vaccinated — and boosted.

Still, omicron may change the equation in subtle ways. To get an idea what may lie ahead for the rest of the winter, we spoke to Drexel University virologist Zachary Klase, La Salle University biologist Brian DeHaven, and Columbia University disease modeler Jeffrey Shaman.

The early reports are holding up: This variant does seem to cause milder symptoms than its predecessors. One reason may be that it seems to replicate (make copies of itself) in the upper airways, rather than deep in the lungs, said DeHaven, a La Salle associate professor who studies the immune response to viruses.

But even if a smaller percentage of infected people are experiencing severe illness than before, the number of cases is hitting record levels in much of the country.

“A small percentage of a huge number is still a big number,” he said.

That helps to explain why plenty of hospitals are jammed, he said. This is no time to let down your guard.

What’s more, U.S. infectious-disease chief Anthony Fauci warned last week that even for those in whom omicron results in a milder illness, the “brain fog” and other chronic symptoms known as “long COVID” remain a possibility.

“Long COVID can happen no matter what virus variant occurs,” Fauci told Spectrum News. “There’s no evidence that there’s any difference between delta or beta or now omicron.”

People infected with the omicron variant respond by developing customized antibodies that protect against future infections with the same strain, according to a study from South Africa, where omicron was first identified.

While the results have not yet been reviewed for publication, they came as no surprise to others in the field. That’s how the immune system works.

The good news is that these omicron-specific antibodies also are likely to protect against infection with the delta variant of the virus — though not as well, the researchers found. That, too, was not a big surprise, said Klase, an associate professor in the department of pharmacology and physiology at Drexel’s College of Medicine.

“We keep hearing about how omicron is different, but it’s still the same virus,” he said. “It’s variations on a theme.”

The South African researchers measured the effect of the antibodies on different strains by drawing blood from patients, extracting their antibody-laden plasma, and mixing it with viruses in a lab dish.

While all study participants had been infected with the omicron variant, some had the additional protection of being vaccinated. In general, their antibody levels were even higher than in those who had not been vaccinated, the study results suggested.

Still unclear is the impact of omicron on another arm of the immune system, called T-cells. But so far, evidence suggests that both of the mRNA vaccines, Moderna and Pfizer-BioNTech, result in the production of T-cells that reduce the risk of severe illness from all known strains, DeHaven said.

It has been clear for a while that COVID is here to stay in some form. The question is when it will subside to the “endemic” level: still circulating, but not out of control.

Epidemiology models suggest that in the U.S., the current wave could start to subside as soon as mid-January, said Shaman, a professor of environmental health sciences at Columbia’s Mailman School of Public Health.

But another wave could still lie ahead, he said.

“Over the course of a decade, we’ll get a sense for how often we’ll deal with outbreaks and how rough they are,” he said. “Is it every five years? Is it every year? Every six months?”

He and DeHaven both cautioned against the widespread notion that viruses always evolve to become less virulent — causing less severe disease. While that phenomenon seems to have occurred with omicron, future strains could evolve in the opposite direction.

“There’s nothing that says omicron can’t pick up more harmful mutations,” DeHaven said.

With some other kinds of viruses, it is true that evolution favors the development of less-virulent strains. Variants that spread easily are, by definition, the ones that stick around. So if, for example, a virus kills its host quickly, the virus itself is also likely to die out.

But with the coronavirus, people are able to spread illness before they develop symptoms. It doesn’t matter if they go on to become very sick, Shaman said.

Maybe omicron represents the last big wave for a while. But as the pandemic has taught us time and again, the situation can change quickly, DeHaven said.

“If people hear that and say this doesn’t matter anymore,” he said, “that could cause a situation where this isn’t the last wave.”