This 2020 electron microscope image made available by the Centers for Disease Control and Prevention shows SARS-CoV-2 virus particles which cause COVID-19. According to research released in 2021, evidence is mounting that having COVID-19 may not protect against getting infected again with some of the new variants. (Photo by The ASSOCIATED PRESS)

This 2020 electron microscope image made available by the Centers for Disease Control and Prevention shows SARS-CoV-2 virus particles which cause COVID-19. According to research released in 2021, evidence is mounting that having COVID-19 may not protect against getting infected again with some of the new variants. (Photo by The ASSOCIATED PRESS)

New variants raise worry about COVID-19 virus reinfections

Evidence is mounting that having COVID-19 may not protect against getting infected again with some of the new variants. People also can get second infections with earlier versions of the coronavirus if they mounted a weak defence the first time, new research suggests.

How long immunity lasts from natural infection is one of the big questions in the pandemic. Scientists still think reinfections are fairly rare and usually less serious than initial ones, but recent developments around the world have raised concerns.

In South Africa, a vaccine study found new infections with a variant in 2% of people who previously had an earlier version of the virus.

In Brazil, several similar cases were documented with a new variant there. Researchers are exploring whether reinfections help explain a recent surge in the city of Manaus, where three-fourths of residents were thought to have been previously infected.

In the United States, a study found that 10% of Marine recruits who had evidence of prior infection and repeatedly tested negative before starting basic training were later infected again. That work was done before the new variants began to spread, said one study leader, Dr. Stuart Sealfon of the Icahn School of Medicine at Mount Sinai in New York.

“Previous infection does not give you a free pass,” he said. “A substantial risk of reinfection remains.”

Reinfections pose a public health concern, not just a personal one. Even in cases where reinfection causes no symptoms or just mild ones, people might still spread the virus. That’s why health officials are urging vaccination as a longer-term solution and encouraging people to wear masks, keep physical distance and wash their hands frequently.

“It’s an incentive to do what we have been saying all along: to vaccinate as many people as we can and to do so as quickly as we can,” said Dr. Anthony Fauci, the U.S. government’s top infectious disease expert.

“My looking at the data suggests … and I want to underline suggests … the protection induced by a vaccine may even be a little better” than natural infection, Fauci said.

Doctors in South Africa began to worry when they saw a surge of cases late last year in areas where blood tests suggested many people had already had the virus.

Until recently, all indications were “that previous infection confers protection for at least nine months,” so a second wave should have been “relatively subdued,” said Dr. Shabir Madhi of the University of the Witwatersrand in Johannesburg.

Scientists discovered a new version of the virus that’s more contagious and less susceptible to certain treatments. It now causes more than 90% of new cases in South Africa and has spread to 40 countries including the United States.

Madhi led a study testing Novavax’s vaccine and found it less effective against the new variant. The study also revealed that infections with the new variant were just as common among people who had COVID-19 as those who had not.

“What this basically tells us, unfortunately, is that past infection with early variants of the virus in South Africa does not protect” against the new one, he said.

In Brazil, a spike in hospitalizations in Manaus in January caused similar worry and revealed a new variant that’s also more contagious and less vulnerable to some treatments.

“Reinfection could be one of the drivers of these cases,” said Dr. Ester Sabino of the University of Sao Paulo. She wrote an article in the journal Lancet on possible explanations. “We have not yet been able to define how frequently this is happening,” she said.

California scientists also are investigating whether a recently identified variant may be causing reinfections or a surge of cases there.

“We’re looking at that now,” seeking blood samples from past cases, said Jasmine Plummer, a researcher at Cedars-Sinai Medical Center in Los Angeles.

Dr. Howard Bauchner, editor-in-chief of the Journal of the American Medical Association, said it soon would report on what he called “the Los Angeles variant.”

New variants were not responsible for the reinfections seen in the study of Marines — it was done before the mutated viruses emerged, said Sealfon, who led that work with the Naval Medical Research Center. Other findings from the study were published in the New England Journal of Medicine; the new ones on reinfection are posted on a research website.

The study involved several thousand Marine recruits who tested negative for the virus three times during a two-week supervised military quarantine before starting basic training.

Among the 189 whose blood tests indicated they had been infected in the past, 19 tested positive again during the six weeks of training. That’s far less than those without previous infection — “almost half of them became infected at the basic training site,” Sealfon said.

The amount and quality of antibodies that previously infected Marines had upon arrival was tied to their risk of getting the virus again. No reinfections caused serious illness, but that does not mean the recruits were not at risk of spreading infection to others, Sealfon said.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Red Deer Public Schools says that in the absence of additional funds from the provincial government, there was no consideration of using alternate classroom sites in the district. (AP Photo/Gregory Bull)
Red Deer Public Schools launches online engagement process

Red Deer Public schools is seeking community input to help ensure a… Continue reading

Red Deer Rebels defenceman Mason Ward battles with a Medicine Hat Tigers’ forward during the WHL Central Division season opener. (Photo by Rob Wallator/ Red Deer Rebels)
Tigers come back to spoil Red Deer Rebels home opener

It’s been nearly 345 days since the Red Deer Rebels last played… Continue reading

Students walk into Hunting Hills High School, which is one of the Red Deer Public Schools with solar panels on its roof. (Photo by SEAN MCINTOSH/Advocate staff)
Red Deer high school was placed in lockdown following potential threat

Hunting Hills High School was placed in a lockdown Friday after Red… Continue reading

Red Deer Mayor Tara Veer says some details of the provincial government’s 2021-22 budget need to be ‘sorted out’ when it comes to the hospital expansion funding. (File photo by Advocate staff)
More detail needed regarding hospital funding, says Red Deer mayor

Red Deer Mayor Tara Veer says some information is unclear regarding the… Continue reading

Alberta Health reported two new COVID-19 deaths in Red Deer Friday. (Image courtesy CDC)
Two more deaths linked to Olymel outbreak in Red Deer

Province reported 356 additional COVID-19 cases Friday

An arrest by Red Deer RCMP is facing online scrutiny. No charges have been laid and the incident is still under investigation. (Screenshot of YouTube video)
Red Deer RCMP investigating violent arrest caught on video

Police say officer ‘acted within the scope of his duties’

Runner Melissa Bishop-Nriagu speaks to the media at the opening news conference at the Canadian Track and Field Championships Thursday, July 25, 2019 in Montreal.THE CANADIAN PRESS/Ryan Remiorz
Canadian athletes struggling to find competition as they try to qualify for Tokyo

Canadian athletes struggling to find competition as they try to qualify for Tokyo

New York Red Bulls midfielder Jared Stroud, right, vies for the ball against Toronto FC midfielder Jonathan Osorio during an MLS soccer match in Harrison, NJ., Sunday, Nov. 8, 2020. Entering his ninth season with Toronto FC, Jonathan Osorio said his off-season regimen was no different than in the past. THE CANADIAN PRESS/AP-Eduardo Munoz Alvarez
Veteran TFC midfielder Jonathan Osorio looks to take it to the next level this season

Veteran TFC midfielder Jonathan Osorio looks to take it to the next level this season

Powell, Lowry help depleted Raptors beat Rockets

Powell, Lowry help depleted Raptors beat Rockets

Edmonton Oilers goalie Mikko Koskinen (19) makes the save on Toronto Maple Leafs' Zach Hyman (11) as Tyson Barrie (22) defends during third period NHL action in Edmonton, Saturday, Jan. 30, 2021. Toronto continues to lead the North Division standings, but hard-charging Edmonton is now just four points back on the all-Canadian circuit heading into a three-game series between the teams in Alberta's capital beginning Saturday. THE CANADIAN PRESS/Jason Franson
Maple Leafs, Oilers set for key three-game series atop North Division

Maple Leafs, Oilers set for key three-game series atop North Division

Angela James stands on centre ice in front of the Toronto Maple Leafs team after being inducted into the Hockey Hall of Fame before Toronto Maple Leafs and Buffalo Sabres NHL hockey action in Toronto on Saturday November 6, 2010. THE CANADIAN PRESS/Chris Young
Hall of Famers James, Lowe, Hay named to Order of Hockey in Canada

Hall of Famers James, Lowe, Hay named to Order of Hockey in Canada

Toronto Raptors head coach Nick Nurse talks to center Aron Baynes (46) and guard Norman Powell (24) during the second half of an NBA basketball game against the Philadelphia 76ers Sunday, Feb. 21, 2021, in Tampa, Fla. THE CANADIAN PRESS/AP-Chris O'Meara
Nurse, five Raptors assistants sidelined to due COVID-19 health and safety protocols

Nurse, five Raptors assistants sidelined to due COVID-19 health and safety protocols

Team Ontario skip Rachel Homan, centre, makes a shot against Team Wild Card 1 as second Sarah Wilkes, left, and lead Joanne Courtney sweep at the Scotties Tournament of Hearts in Calgary, Alta., Friday, Feb. 26, 2021. Ontario's Rachel Homan kicked off play in the championship pool Friday with a 7-6 victory over Chelsea Carey of Team Wild Card One at the Canadian women's curling playdowns. THE CANADIAN PRESS/Jeff McIntosh
Homan and Einarson improve to 8-1 at Canadian women’s curling championship

Homan and Einarson improve to 8-1 at Canadian women’s curling championship

Prime Minister Justin Trudeau rises during question period in the House of Commons on Parliament Hill in Ottawa on Wednesday, Feb. 24, 2021. THE CANADIAN PRESS/Sean Kilpatrick
New vaccine brings optimism amid rising threat of variants, high case counts

New vaccine brings optimism amid rising threat of variants, high case counts

Most Read