It may be possible for people who got Omicron to be reinfected with it, Ontario experts say
As many as four million Ontarians may have been infected with the Omicron variant, according to the province's science advisers, but their illnesses -- particularly the milder ones -- may not stop them from getting reinfected.
It's too early to know for certain, but it doesn't seem like Omicron provides durable immunity against COVID-19, said epidemiologist and University of Ottawa associate professor Raywat Deonandan.
"The hope was that Omicron rips through the population, doesn't render a lot of suffering, and leaves behind the gift of immunity," he said.
"That is now in question. But it might be possible that if you get reinfected multiple times, maybe then you'll get something resembling ... durable immunity. It's too early to know. Signs are not pointing in a positive direction."
A recent preprint study -- one that has not been peer-reviewed -- suggested that mild Omicron infection doesn't render enough immunity to prevent future infections, while infections from the Delta variant, which tended to be more severe, produced higher protection.
Dr. Fahad Razak, an internist and member of the province's science advisory table, said Ontario is not seeing "significant" numbers right now of people with more than one Omicron infection.
But milder illnesses that give people congestion, cough, fever, and leave them feeling unwell but not so sick that they need to go to the hospital -- like many Omicron infections -- may leave people more susceptible to reinfection, he said.
"The parts of your immune system that protect against those milder infections, they tend to wane much faster than the parts of your immune system that protect against the more severe infection," Razak said.
Omicron probably provides some short-term protection from reinfection, but there may not be long-term protection, said University of Toronto immunology professor Tania Watts. The combination of vaccination and infection is much better, she said.
"One thing our vaccines do is they give us what we call systemic immunity, because you inject it in the muscle, and the antibodies circulate around our body," she said.
But the reason that immunity starts to wane is that people need those antibodies in the nose and throat, where the virus enters, she said.
"So when you get an infection, after two doses of vaccine, it can actually pull that immune response rapidly into the nose, and it leaves behind cells and those tissues that will respond again," Watts said.
People who received two doses of a COVID-19 vaccine and then got Omicron will "almost certainly" see an immunity boost, she said, but that may not hold true for unvaccinated people who get Omicron.
Dr. Kieran Moore, Ontario's chief medical officer of health, said getting vaccinated plus receiving an mRNA booster dose "significantly" adds to people's level and length of protection against Omicron, but for unvaccinated people who get infected their immunity may not last as long.
"It appears with Omicron, if you get natural immunity -- so you're not vaccinated and you get infected by Omicron -- you do have some immunity against further reinfection," Moore said.
"But there is significantly a risk for reinfection from Omicron over time. So we're not confident in how long that duration of immunity is from natural exposure yet. It's still early days."
Available figures from Public Health Ontario show there have been 3,208 confirmed cases of COVID-19 reinfections since Nov. 1, 2020, although the data does not indicate what strain of the virus individuals were infected with.
Case numbers since late December -- after Omicron became dominant -- are likely an undercount, since the province has limited access to PCR testing, and therefore genomic sequencing, since then.
This report by The Canadian Press was first published Feb. 4, 2022.
CTVNews.ca Top Stories
Former homicide detective explains how police will investigate shooting outside Drake's Bridle Path mansion
Footage from dozens of security cameras in the area of Drake’s Bridle Path mansion could be the key to identifying the suspect responsible for shooting and seriously injuring a security guard outside the rapper’s sprawling home early Tuesday morning, a former Toronto homicide detective says.
Federal government grants B.C.'s request to recriminalize hard drugs in public spaces
The federal government is granting British Columbia's request to recriminalize hard drugs in public spaces, nearly two weeks after the province asked to end its pilot project early over concerns of public drug use.
Stormy Daniels describes meeting Trump during occasionally graphic testimony in hush money trial
Stormy Daniels took the witness stand Tuesday at Donald Trump's hush money trial, describing for jurors a sexual encounter the porn actor says she had with him in 2006 that resulted in her being paid off to keep silent during the presidential race 10 years later.
MPs agree Canadian gov't should improve new disability benefit
The federal government needs to safeguard the incoming Canada Disability Benefit from clawbacks and do more to ensure it actually meets the stated aim of lifting people living with disabilities out of poverty, MPs from all parties agree.
Bye-bye bag fee: Calgary repeals single-use bylaw
A Calgary bylaw requiring businesses to charge a minimum bag fee and only provide single-use items when requested has officially been tossed.
CFL suspends Argos QB Chad Kelly at least nine games following investigation
The CFL suspended Toronto Argonauts quarterback Chad Kelly for at least nine regular-season games Tuesday following its investigation into a lawsuit filed by a former strength-and-conditioning coach against both the player and club.
Boy Scouts of America changing name for first time in 114 years, aiming for inclusivity
The Boy Scouts of America is changing its name for the first time in its 114-year history and will become Scouting America. It's a significant shift as the organization emerges from bankruptcy following a flood of sexual abuse claims and seeks to focus on inclusion.
opinion Tom Mulcair: Trudeau's handling of Poilievre's 'wacko' House turfing a clear sign of Liberal desperation
When Speaker Greg Fergus tossed out Pierre Poilievre from the House last week, "those of us who have experience as parliamentarians simply couldn't believe our eyes," writes former NDP leader Tom Mulcair in his column for CTVNews.ca
New charges for Ont. woman who previously admitted to defrauding doulas
The Brantford, Ont. woman who was previously sentenced to house arrest after admitting to deceiving doulas has been charged again in connection to a new victim.