Waning protection from 2 doses shows need for COVID-19 boosters, says head of Ontario's science table

Protection provided by COVID-19 vaccines against infection by the novel coronavirus has waned dramatically since the highly-infectious Omicron variant started spreading across Ontario, according to data from the province’s COVID-19 Science Advisory Table.

Third dose can increase protection by as much as 5 times, says scientific director Dr. Peter Jüni

Dr. Sabra Gibbons administers COVID-19 vaccine during a drive through clinic at St. Lawrence College in Kingston, Ont., Saturday, Dec. 18. (Lars Hagberg/The Canadian Press)

Protection provided by COVID-19 vaccines against infection by the novel coronavirus has waned dramatically since the highly infectious Omicron variant started spreading across Ontario, according to data from the province's Science Advisory Table.

The data shows that while having two doses does protect against severe illness among those who contract the virus, its ability to prevent infection altogether is plummeting, said Dr. Peter Jüni, the group's scientific director.

Vaccine protection has fallen to 14.9 per cent — from nearly 90 per cent a month ago — for people who have received two doses, according to the data. 

"Vaccine protection against infection is melting like snow under the sun," Jüni said in an interview on CBC News Network. "Omicron is evading the immune system.

"In reality, there is no way — if it comes to infection — to distinguish anymore between a person who is not vaccinated and a person who has received two doses."

Vaccine protection refers to the reduction in the risk of getting infected.

WATCH | Dr. Peter Jüni discusses importance of boosters:

Drop in 2-dose protection underscores need for accelerated booster campaign

2 years ago
Duration 5:18
Dr. Peter Jüni, the scientific director of Ontario's COVID-19 Science Advisory Table and professor of medicine and epidemiology at the University of Toronto, says COVID-19 vaccines still provide protection 'against serious outcomes' and stressed the importance of boosters in the province. (Credit: Evan Mitsui/CBC)

Data shows boosters decrease risk

Jüni said data from the U.K. has shown a third dose of a COVID-19 vaccine can decrease the risk of infection by up to five times, and he called for an acceleration of the campaign to provide them.

This chart from the Ontario COVID-19 Science Advisory Table's online dashboard shows data for how protective vaccines are against infection, hospitalization and ICU admission. (Ontario COVID-19 Science Advisory Table)

"We need to get these doses into people's arms as soon as possible so you see this purple line again go up," Jüni said, referencing the above chart. "Based on everything we know, you'll probably need to wait roughly two weeks before the third dose offers full protection again. 

"Full protection means then that your risk of getting infected is decreased roughly by four to five fold."

Omicron contains more than 30 mutations in the spike protein — the part of the coronavirus that helps it enter human cells — some of which are associated with resistance to neutralization from antibodies. 

Ontario discovered its first case of the Omicron variant on Nov. 28, just days after South African researchers alerted the world to its existence. Around three weeks later, Omicron became the dominant variant, making up the majority of new daily infections in the province.

2 doses prevent severe outcomes: data

Despite the clear weakening in protection from infection, the data shows that two doses continue to offer over 90 per cent protection against hospitalization and intensive care unit admission. 

Jüni said that's proof that the vaccines have been successful at achieving their primary goal, although he warned that the situation could change in the coming days and weeks because, up until now, most people who have been hospitalized with COVID-19 were infected with the previously dominant Delta variant. 

"Only in the next few days, we will start to see an uptick in patients admitted for Omicron infections," said Jüni. "That's the delay you typically see.… We saw the uptick in case numbers for Omicron and now we will see the uptick in hospitalizations."

9,418 new cases Monday

Ontario reported 9,418 new cases on Monday, according to Health Minister Christine Elliott, a slight dip in infections after hitting a record-high 10,412 cases on Saturday and logging 9,826 cases on Boxing Day.

The rolling seven-day average of new daily cases now stands at 7,550, up from 2,863 one week ago.

Experts have said the actual number of cases is likely far higher than those reported each day, because many public health units have reached their testing capacity.

Public Health Ontario reported an additional five deaths linked to COVID-19 on Monday, pushing the provincial death toll to 10,162.

Health Minister Christine Elliott said there were 480 people hospitalized with COVID-19 and 176 of them were in intensive care units. 

The number of people hospitalized increased from 373 on Sunday, although she noted that not all hospitals report COVID-19 data on weekends.

The seven-day rolling average for COVID patients in the ICU is 168, Elliott said.

Elliott said more than 45,000 doses of COVID-19 vaccines were administered on Boxing Day.

"Thank you, #TeamOntario, for taking time out of your holidays to get shots into arms," she tweeted.

COVID-19 data will be limited over the holidays, as the Ministry of Health will not be updating its website until Dec. 29.

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