A woman is vaccinated against COVID-19 in Lawley, south of Johannesburg, South Africa, Dec. 1, 2021.Shiraaz Mohamed/The Associated Press
The Omicron variant is three times more likely to cause reinfection in people, compared with earlier variants of the coronavirus, new data from South Africa suggest.
The study, released Thursday, is the first strong indication of why Omicron has surged so rapidly in countries such as South Africa, where a large percentage of the population was thought to have developed immunity to COVID-19 as a result of prior infection.
It has huge implications for countries such as India and many African countries with low vaccination rates, where immunity had been achieved largely through infection. Even if the new variant is not more transmissible than other variants, such as Delta, it could still spread more rapidly because people are more vulnerable to it, scientists say.
Proportion of the different COVID-19 variants of concern reported weekly in South Africa since October 2020
Alpha
Beta
Delta
Omicron
Other
100%
80
60
40
20
0
Oct. 1,
2020
Jan. 14,
2021
Apr. 29
Aug. 12
Nov. 18
SOURCE: REUTERS
Proportion of the different COVID-19 variants of concern reported weekly in South Africa since October 2020
Alpha
Beta
Delta
Omicron
Other
100%
80
60
40
20
0
Oct. 1,
2020
Jan. 14,
2021
Apr. 29
Aug. 12
Nov. 18
SOURCE: REUTERS
Proportion of the different COVID-19 variants of concern reported weekly in South Africa since October 2020
Alpha
Beta
Delta
Omicron
Other
100%
80
60
40
20
0
Oct. 1, 2020
Jan. 14, 2021
Apr. 29
Aug. 12
Nov. 18
SOURCE: REUTERS
“It’s the susceptibility of the population that is greater now,” said Anne von Gottberg of the National Institute for Communicable Diseases (NICD) in South Africa, one of the authors of the preprint study.
“Previous infection used to protect against Delta, and now with Omicron that doesn’t seem to be the case,” she told a briefing at the African office of the World Health Organization.
Vaccines will be the best weapon against the new variant, scientists say. Vaccines are likely to protect people against severe illness, hospitalization and death from the Omicron variant, Prof. von Gottberg told the briefing.
It is too early to know the severity of Omicron cases, although so far there is no indication that it is causing more severe illness.
South Africa, the first country to detect and report it to the WHO last week, is emerging as the world’s hotspot for the variant, with more confirmed cases than any other country.
Seven vaccine makers’ COVID-19 boosters raise immune response, British study says
Ontario, Alberta lower age of eligibility of COVID-19 booster shots amid concerns over case counts
Why Omicron’s list of mutations is raising concerns among COVID-19 vaccine makers and health experts
Omicron is driving a dramatic surge of infections in South Africa, and about three-quarters of new cases are believed to involve the new variant, based on laboratory sequencing of samples.
On Thursday, health authorities reported more than 11,500 new cases in South Africa. The number has almost tripled in the past two days and increased fivefold since Monday.
The daily positivity rate has doubled to 22 per cent in the same four-day period, meaning that more than one-fifth of tests are finding cases of the virus. The positivity rate was less than 2 per cent in mid-November.
The vast majority of cases are being discovered in South Africa’s economic heartland, Gauteng province, where Johannesburg and Pretoria are located. The surge in Gauteng is steeper and faster than any previous wave, forcing scientists to recalibrate their projection models. Hospitalizations have also been increasing there, although not as steeply as the increase in cases.
Many countries worldwide have praised South Africa for detecting and identifying the new variant as swiftly and transparently as it did – but have also imposed strict bans on travellers from South Africa, inflicting massive damage on the country’s tourism industry.
Omicron variant detected around world
The World Health Organization classified Omicron as a “variant of concern,” due to the number of mutations that might help it spread or evade antibodies from prior infection or vaccination. The variant has now been detected on every continent outside of Antarctica.
First detected in South Africa and Botswana last week
Note: As of Dec. 1
SOURCE: REUTERS
Omicron variant detected around world
The World Health Organization classified Omicron as a “variant of concern,” due to the number of mutations that might help it spread or evade antibodies from prior infection or vaccination. The variant has now been detected on every continent outside of Antarctica.
First detected in South Africa and Botswana last week
Note: As of Dec. 1
SOURCE: REUTERS
Omicron variant detected around world
The World Health Organization classified Omicron as a “variant of concern,” due to the number of mutations that might help it spread or evade antibodies from prior infection or vaccination. The variant has now been detected on every continent outside of Antarctica.
First detected in South Africa and Botswana last week
Note: As of Dec. 1
SOURCE: REUTERS
The preprint study is based on test results from 2.8 million South Africans who had confirmed cases of the virus since March 2020. The data show that the risk of reinfection has increased threefold since early October as the new variant has taken hold. The study is considered a preprint because it has not been subjected to peer review.
“Population-level evidence suggests that the Omicron variant is associated with substantial ability to evade immunity from prior infection,” the study concluded.
It said the data suggest that the “selection advantage” of the new variant “is at least partially driven by an increased ability to infect previously infected individuals.”
With the emergence of Omicron, South African leaders have been intensifying their efforts to persuade people to get vaccinated. The message seems to be working. This week, an average of 165,000 people a day have been getting vaccinated – an increase of about 30 per cent over last week. Officials are trying to accelerate the campaign by setting up new vaccination sites in shopping centres, high schools and transport hubs.
More than 36 per cent of South African adults have been fully vaccinated so far. The rate is high compared with those of most other African countries but lower than those of wealthier countries, primarily because of lengthy delays in obtaining vaccine supplies.
President Cyril Ramaphosa has announced that the government will consider making vaccines a mandatory rule for access to some places and activities, although no details have been decided so far. A growing number of businesses and labour unions have voiced support for vaccine mandates.
Sign up for the Coronavirus Update newsletter to read the day’s essential coronavirus news, features and explainers written by Globe reporters and editors.