Local modeling

Computer modeling by public health experts shows unvaccinated people cause disproportionately higher COVID-19 infections

Report concludes coronavirus will continue until people are vaccinated

Unvaccinated people create a much higher risk of COVID-19 infection for vaccinated people according to a computer modeling study published in the latest issue of the Canadian Medical Association Journal (CMAJ)

The study was authored by David N. Fisman, Afia Amoako and Ashleigh R. Tuite, a group of researchers from the University of Toronto’s Dalla Lana School of Public Health. Their article was published on Monday, April 25, 2022.

They wrote that the study consisted of a disease model with two connected subpopulations; people who have been vaccinated and people who have not. Vaccinated is assumed to refer to people who received two doses, since Ontario public health officials have referred to recipients of a single dose as partially vaccinated.

The report says the study simulated random mixing patterns between vaxxed and non-vaxxed groups as well as similar mixing.

“We assessed the dynamics of an epidemic within each subgroup and in the population as a whole,” the report said.

The report says the higher risk presented by unvaccinated people “was disproportionate” and that unvaccinated people contributed to infections among vaccinated people at a higher rate than expected based on contact numbers alone.

“Although the risk associated with avoidance of vaccination during a virulent pandemic falls primarily on unvaccinated people, their choices affect the risk of viral infection in vaccinated people disproportionately to the proportion of unvaccinated people in the population,” the report said.

The authors said the interpretation of their work is that whatever precautions are taken, “a substantial proportion of new cases can be expected to occur” among vaccinated people when interacting with those who are not vaccinated.

“Notwithstanding the simplicity of the model, it provides a graphical representation of the expectation that even with highly effective vaccines, and in the face of high vaccination coverage, a substantial proportion of new cases can be expected to occur among people vaccinated, so rates, rather than absolute numbers, represent the appropriate measure to present the impact of vaccination However, we find that the degree to which people interact differently with other people who look like them is likely to have an important impact on the dynamics of the disease and on the risk in people who choose to be vaccinated,” the study states.

The report concludes that the choice the unvaccinated make is likely to affect those who are vaccinated and lead to the continuation of the virus.

“Using simple mathematical modeling, we have shown that although the risk associated with avoidance of vaccination during a virulent pandemic falls primarily on those who are unvaccinated, some people’s choice to refuse vaccination is likely to affect the health and safety of vaccinated people in a disproportionate way to the fraction of unvaccinated people in the population,” the report states.

“The risk in the unvaccinated cannot be considered selfish, and considerations of fairness and justice for those who choose to be vaccinated, as well as those who choose not to be vaccinated, must be taken. taken into account in the formulation of the vaccination policy. unlikely that SARS-CoV-2 will be eliminated, and our findings will likely be relevant to future seasonal outbreaks of SARS-CoV-2 or in the face of emerging variants,” the report concludes.