Nearly 80 per cent of the Canadian population is vaccinated with at least two doses of the COVID-19 vaccine. But with studies pointing to the protective benefits of these vaccines, it may be puzzling to see that the majority of virus-related hospitalizations in most provinces involve people who are fully vaccinated against the disease.
In Quebec, for example, health officials reported 160 new COVID-19-related hospitalizations on Feb. 5 among those aged five and older. This figure includes patients in hospital wards and intensive care units (ICUs). Of these hospitalizations, 118 were among those who were vaccinated with either two or three doses of the COVID-19 vaccine. Five hospitalizations involved partially vaccinated residents and 32 hospitalized patients were either unvaccinated or received their first dose within less than 14 days. No vaccine status was specified for four additional COVID-19-related hospitalizations.
Dr. Christopher Labos is a cardiologist and epidemiologist based in Montreal. When looking at the raw data, the explanation behind why more fully vaccinated people were admitted to hospital as opposed to unvaccinated people is simple, he said.
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“There are more vaccinated people out there,” he told CTVNews.ca in a phone interview on Wednesday. “When the vaccinated make up 80 to 90 per cent of the population, they will make up more of the hospitalizations.”
When looking at the numbers of vaccinated and unvaccinated people among COVID-19-related hospitalizations, it’s important to put these figures into context, Labos said. Approximately 7.39 million Quebec residents aged five and older have their first dose of the COVID-19 vaccine, and 6.93 million residents have their first two doses. Although 118 of the COVID-19 patients newly admitted to hospital were fully vaccinated, when divided by the total number of fully vaccinated people in Quebec, this represents a rate of about 17 hospitalizations per one million people.
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With 32 unvaccinated COVID-19 patients in hospital out of a total of about 810,000 unvaccinated people in the province aged five and older at the time, this represents about 39.5 hospitalizations per one million people.
“The unvaccinated make up a greater proportion of the hospitalized patients,” he said. “It’s really about adjusting for the fact that you have different population sizes.”
Dr. Nazeem Muhajarine is an epidemiologist at the University of Saskatchewan. He used the example of a population of 100 people, 90 of whom are fully vaccinated against COVID-19 and 10 of whom are not. If five of the 90 people who are vaccinated become hospitalized and five of the 10 unvaccinated people are admitted to hospital, it may appear as though there’s a 50/50 chance of being hospitalized, he said, but that is not actxjmtzywually the case.
“Five out of 90 is quite a different proportion compared to five out of 10,” Muhajarine told CTVNews.ca on Wednesday in a phone interview. “In this case, we are not looking at the base, or the total number of people who are out there in the population who are vaccinated versus unvaccinated – we are ignoring that piece of information.”
AGE AN IMPORTANT RISK FACTOR TO CONSIDER
Another key factor to consider is the age of patients currently in hospital with COVID-19, said Dr. Peter Juni, head of the Ontario COVID-19 Science Advisory Table. Those who are older are at greater risk of COVID-19-related hospitalization compared to those who are younger, Juni said. Not only that, but those who are older are more likely to be fully vaccinated than younger populations, according to data compiled by the Public Health Agency of Canada. This is contributing to the high rates of vaccination among hospitalized patients, he said.
“You need to account for age,” Juni told CTVNews.ca in a phone interview on Wednesday. “Age is the most important risk factor for death, ICU admission and hospital admission.”
According to data from the Ontario science table, the total number of hospital patients with COVID-19 who have at least two vaccine doses exceeds the number of hospital patients with the virus who aren’t vaccinated at all, said Juni. When accounting for total population and differences in the risk of severe disease among all ages, the rate of COVID-19-related hospitalization among those with at least two vaccine doses is 124.9 per million as of Feb. 6. Meanwhile, the rate of COVID-19-related hospitalization among unvaccinated people is 756.1 per million. Figures are based on seven-day averages and include patients in hospital wards and ICUs.
“Who has the higher risk? It’s simple,” said Juni.
Multiplying the rate of unvaccinated people per million by 14.7 to account for approximately 14.7 million people living in Ontario shows that the province would currently be seeing about 11,085 COVID-19 patients in hospital if everyone were unvaccinated, said Juni. If the entire population of Ontario was fully vaccinated, that number would drop down to about 1,832 hospital patients.
Also accounting for age, data from Quebec demonstrates that those who are unvaccinated have 5.9 times the risk of COVID-19-related hospitalization and 10 times the risk of ICU admission compared to those who are vaccinated against the virus with two doses.
“When you adjust for population size and when you adjust for age…it becomes pretty clear that the risk of you being hospitalized is much higher if you are unvaccinated,” said Labos. “The numbers can lead you to draw the wrong conclusion if you don’t put them in the right context.”
‘IT’S A NUMERICAL ISSUE’
Muhajarine has been advocating for more transparency around information on the vaccination status of hospitalized patients for months now, he said. In particular, he is pushing for a more accurate depiction of the true risk of hospitalization as a proportion of the total number of people who are vaccinated compared with those who are unvaccinated.
“It’s a numerical issue,” he said. “We should be reporting the true risk of hospitalization as per population in relation to the denominator.”
When it comes to the vaccination status of hospitalized patients with COVID-19 in Saskatchewan, statistics shared by the province’s government are limited, Muhajarine said. Data as of Feb. 6 states that a total of 332 people are hospitalized with COVID-19 in the province. Of this total, 110 patients were not fully vaccinated. No additional details regarding vaccination status were provided.
In several other provinces, the most recent data shows that the majority of COVID-19-related hospitalizations involve those who have at least two doses of the vaccine, including Manitoba, Nova Scotia and Prince Edward Island.
This is also the case in British Columbia. From Jan. 20 to Feb. 2, the province reported a total of 1,289 COVID-19-related hospitalizations. Among them, 887 were among patients who were fully vaccinated with at least two doses of the COVID-19 vaccine, while 339 hospitalizations involved people who were not vaccinated. The remaining 63 people were only partially vaccinated against the virus. After adjusting for age, this translates to about 19 hospitalized cases per 100,000 people involving those who were fully vaccinated, compared to about 88.2 hospitalized cases per 100,000 people among those who were not vaccinated at all.
“The number of vaccinated people and the number of unvaccinated people that wind up being hospitalized looks very similar in terms of absolute number, but it’s a much smaller proportion of the vaccinated than it is of the unvaccinated,” said Dr. Brian Conway, an infectious disease expert and medical director of the Vancouver Infectious Diseases Centre.
DOES THIS MEAN VACCINES DON’T WORK?
While some provinces may be seeing higher numbers of vaccinated patients among new COVID-19-related hospitalizations compared to unvaccinated patients, Labos said this does not necessarily mean that vaccines targeting the virus are ineffective.
Initial studies on the COVID-19 vaccine last year showed 88 per cent efficacy against symptomatic disease from the Delta variant. But with the emergence of the Omicron variant, which has proven to be highly transmissible and better able to evade protection from vaccines, the defence offered by two vaccine doses appears to be reduced against the newest variant of concern.
A recent study conducted in Ontario looked at the effectiveness of two and three doses of the COVID-19 vaccine against Delta and Omicron among about 20,000 patients in December. Results showed that six months after receiving two doses of the COVID-19 vaccine, little protection remained against symptomatic illness from the Omicron variant. However, two doses of the vaccine still protected against hospital admission and death from Omicron, reducing the risk by 82 per cent.
The study also showed that three doses of the vaccine decreased the chances of developing symptomatic illness from Omicron by 61 per cent. A third dose of the COVID-19 vaccine also reduced the risk of hospitalization and death due to the Omicron variant by 95 per cent. The study is a preprint that has been submitted for peer review.
This reaffirms the importance of getting vaccinated, Muhajarine said, referring specifically to the added protection that comes with a third dose of the COVID-19 vaccine.
“These vaccines, particularly the booster dose, protect people really well against serious COVID,” he said, referring to cases where patients require hospital care or intensive care involving intubation or ventilation, as well as death from COVID-19.
By getting vaccinated, Conway said, this further reduces community transmission of the virus. The virus primarily circulates among unvaccinated people in an uncontrolled manner, he said. From there, it can spread to the small proportion of vaccinated individuals who are more susceptible to infection and hospitalization because of age, comorbid conditions, and pre-existing issues with the immune system, he said.
“The reason community-based transmission is staying so high is because the pool of unvaccinated individuals is also remaining stubbornly high,” said Conway. “If we reduce the number of unvaccinated individuals, we will reduce the ability of the virus to spread and we will reduce infections and hospitalizations.
“This is not a sign that vaccines don’t work – it’s a sign that we aren’t yet vaccinating fast enough.”
Still, experts say that other measures must also be put in place to better protect against COVID-19. Labos pointed to initiatives such as wearing masks, vaccine passports, capacity limits and surveillance programs, while Conway used the examples of diligent hand hygiene and physical distancing. Combined with vaccination efforts, these measures will continue to help reduce the public’s risk of contracting COVID-19 and suffering from serious infection, Labos said.
“All of these things work together to minimize the impact of COVID,” he said. “You may not be able to get the risk down to zero but with some very, very basic measures, you can get the risk down to very, very low levels.”
RELATED IMAGESview larger image
Paramedics transfer patients to the emergency room triage but have no choice but to leave them in the hallway due to an at capacity emergency room at the Humber River Hospital during the COVID-19 pandemic in Toronto on Jan. 25, 2022. (THE CANADIAN PRESS/Nathan Denette)
