The majority of new people infected with COVID-19 are triple vaccinated, according to data published daily by the Quebec government. To get an accurate picture of the situation, however, these figures must be put into context.
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“We cannot use the figures we have in Quebec at the moment to determine if vaccination is effective in reducing the number of cases of COVID. Why? Because the sampling is not diffuse across the population,” insists resident doctor Mathieu Nadeau-Vallée, who is known as wal_trudeau on TikTok.
The new cases reported daily by the Quebec government only take into account the results of the PCR screening tests, which have only been accessible since December 2021 to a small part of the Quebec population.
“It’s just certain groups that are sampled, which are special populations and health care workers. So, it is not a sampling that is representative of the total population, ”underlines the TikTok doctor.
“To have data that could tell us about the effectiveness of vaccines in preventing the number of cases, we would have to systematically test people in the communities, and then draw conclusions, but this is not not what we are doing at the moment,” he adds.
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An unrepresentative sample
Among the people who have access to PCR tests, there are in particular health care workers, people aged 70 and over and people who are more vulnerable. These groups are more likely to seek a third dose than the rest of the population.
Although healthcare workers are not obliged to go and get their third dose, they are indeed particularly likely to have received it*. The same goes for people aged 70 and over: 85% of them received three doses of the vaccine, compared to 54% for the general population. The sample is therefore not representative.
“What I suspect is that we are testing a population of people in which the percentage of triple vaccinated is much higher than in the general population. We therefore have an overrepresentation of this group in this sample,” explains Mathieu Nadeau-Vallée.
A 3and effective dose
Without conclusive data in Quebec, we must therefore turn to other countries to measure the effectiveness of the third dose of vaccine against COVID-19. In the United Kingdom, for example, the third dose would be effective between 50 and 60% in reducing the number of cases, suggests the resident doctor.
“It does not mean that a person who has three vaccines cannot catch COVID, it just means that these people have a higher level of antibodies and are better protected against infection”, he concludes. .
* In his TikTok video, Mathieu Nadeau-Vallée argued that health care workers were required to have three doses of vaccine. The majority of healthcare workers instead received a third dose by choice, he said.