Question
I caught Omicron. Am I immune to a reinfection?
I’ve caught COVID-19 even though I am double-vaccinated and have received a booster shot. I’m now feeling pretty miserable but I expect I’ll get better. When I recover, will I be immune to another coronavirus infection? Are five days of isolation really enough? And is the Omicron variant the beginning of the end of the pandemic?
Answer
It’s very likely that you will be well protected against the existing variants of SARS-CoV-2, the coronavirus that causes COVID-19.
Essentially, your immune system has now been exposed to the virus’s spike protein – a key target of antibodies – in two different ways.
“It has seen the spike protein on a live virus and it has seen it in a vaccine,” said Jen Gommerman, a professor of immunology in the Temerty Faculty of Medicine at the University of Toronto.
“That seems to provoke really good immunity. It’s better than just the vaccine alone and it’s better than an infection alone.”
Furthermore, preliminary data indicates that infection by Omicron also provides immunity against earlier variants, such as Delta. As a result, you’re getting a broad range of protection.
Omicron symptoms mirror the flu and common cold. What should I do if I feel sick?
But, possibly more important, an infection can lead to the development of what is known as mucosal immunity. This means you create specialized antibodies in the lining of your nose, mouth and upper airways, where the coronavirus normally invades the body.
“These antibodies are waiting in the mucosa, ready to pounce and attack the virus,” said Andrew Morris, an infectious diseases physician at Sinai Health and the University Health Network in Toronto.
Dr. Gommerman noted that mucosal antibodies are structurally different than the ones that circulate in the bloodstream and are usually generated by vaccines. In particular, they have additional sites that can latch on to their target. So they have an enhanced ability to neutralize the virus.
But she cautioned that there are significant differences in how individuals react when they become infected. “A viral infection is quite variable from person to person,” she explained. In particular, “mucosal immunity will differ in terms of its potency and longevity.”
And even if you have really good mucosal immunity, the number of antibodies – the first line of defence against an intruder – tends to decline over time.
That’s why it is critically important to also get a vaccination, which can stimulate, in a controlled and reliable manner, the production of other immune cells such as killer T cells. If the virus evades the antibodies, a killer T cell can spot an infected cell and destroy it.
There’s no doubt that Omicron is highly contagious and capable of causing breakthrough infections in people who are vaccinated. Some health officials have said Omicron is so ubiquitous that almost everyone will eventually be exposed to it.
“I’ve heard people say that they might as well just get it – and get it over with,” Dr. Gommerman said. She thinks “it’s misguided” to intentionally seek out the virus.
Although current evidence suggests Omicron is less likely to cause severe illness than earlier variants, “we don’t yet know what the long-term effects are going to be,” she explained.
One concern is that you may develop “long COVID,” with symptoms persisting for an indefinite period.
To make matters worse, she said, infected individuals run the risk of spreading the virus to vulnerable people who will be unable to shake off the illness and may need hospitalization – putting an additional burden on the already overstretched health care system.
So if you inadvertently – not intentionally – get infected, how do you best protect others? You should stay home and self-isolate. But for how long?
Several provinces – including British Columbia and Alberta – have lowered the recommended isolation period from 10 to five days for fully vaccinated people without symptoms. Their actions follow similar changes made by the U.S. Centers for Disease Control and Prevention.
The new guidance reflects the fact that Omicron has a much faster life cycle than previous variants. What’s more, fully vaccinated people tend to be infectious for a shorter period than those who aren’t inoculated.
With so many people’s lives placed on hold by quarantines, public-health officials felt the need to revise their guidelines.
But some doctors now worry that certain individuals will still be shedding the virus beyond five days. A few experts have called for the use of rapid antigen tests – to confirm non-infectiousness – before resuming regular activities. Ontario recently added a testing recommendation for those who want to leave quarantine before their five days are up.
However, testing also has drawbacks, Dr. Morris said. For one thing, not everyone has access to testing kits. And one study suggested that certain brands of the test may not be sensitive enough to detect the Omicron variant.
“None of the strategies is ideal. That’s why everyone is struggling with what do,” he said.
Sticking with 10 days “could paralyze the system,” he said, while five days may let the virus spread even more. “Seven days might be the sweet spot in certain cases.”
In fact, Quebec has isolation periods that vary with different groups. It’s five days for most vaccinated people but seven for health-care workers who are in direct contact with patients.
Meanwhile, there is much hope that Omicron could mark the beginning of the end of the pandemic. Many doctors, though, say it’s quite possible we could see even more variants – especially when a large part of the world remains unvaccinated.
“I don’t think we will be able to eradicate this virus from the human population,” said Samira Mubareka, an infectious diseases physician and virologist at Sunnybrook Health Sciences Centre in Toronto.
“But that doesn’t have to be a doomsday message,” she added.
“We actually have vaccines that can be modified to deal with new variants.”
And there are more immediate actions that can be taken to curb the transmission of Omicron. Indeed, good air ventilation, physical distancing, staying home when sick and high-quality masks, worn correctly, can make a difference.
“We just have to make sure we are doing those things properly,” Dr. Mubareka said.
Paul Taylor is a former patient navigation adviser at Sunnybrook Health Sciences Centre and a former health editor of The Globe and Mail.
Paul Taylor