From the Journals

My choice? Unvaccinated pose outsize risk to vaccinated



Mandates and passports

“Our model provides support for vaccine mandates and passports during epidemics, such that vaccination is required for people to take part in nonessential activities,” said Dr. Fisman. The choice to not be vaccinated against COVID-19 should not be considered “self-regarding,” he added. “Risk is self-regarding when it only impacts the person engaging in the activity. Something like smoking cigarettes (alone, without others around) creates a lot of risk over time, but if nobody is breathing your secondhand smoke, you’re only creating risk for yourself. By contrast, we regulate, in Ontario, your right to smoke in public indoor spaces such as restaurants, because once other people are around, the risk isn’t self-regarding anymore. You’re creating risk for others.”

The authors also noted that the risks created by the unvaccinated extend beyond those of infection by “creating a risk that those around them may not be able to obtain the care they need.” They recommended that considerations of equity and justice for people who do choose to be vaccinated, as well as those who choose not to be, need to be included in formulating vaccination policy.

Illuminating the discussion

Asked to comment on the study, Matthew Oughton, MD, assistant professor of medicine at McGill University, Montreal, said: “It is easy to dismiss a mathematical model as a series of assumptions that leads to an implausible conclusion. ... However, they can serve to illustrate and, to an extent, quantify the results of complex interactions, and this study does just that.” Dr. Oughton was not involved in the research.

During the past 2 years, the scientific press and the general press have often discussed the individual and collective effects of disease-prevention methods, including nonpharmaceutical interventions. “Models like this can help illuminate those discussions by highlighting important consequences of preventive measures,” said Dr. Oughton, who also works in the division of infectious diseases at the Jewish General Hospital, Montreal.

It’s worth noting that the authors modeled vaccine effectiveness against all infection, “rather than the generally greater and more durable effects we have seen for vaccines in prevention of severe infection,” said Dr. Oughton. He added that the authors did not include the effect of vaccination in reducing forward transmission. “Inclusion of this effect would presumably have reduced overall infectious burden in mixed populations and increased the difference between groups at lower levels of mixing between populations.”

The research was supported by a grant from the Canadian Institutes of Health Research. Dr. Fisman has served on advisory boards related to influenza and SARS-CoV-2 vaccines for Seqirus, Pfizer, AstraZeneca, and Sanofi-Pasteur Vaccines and has served as a legal expert on issues related to COVID-19 epidemiology for the Elementary Teachers Federation of Ontario and the Registered Nurses Association of Ontario. Dr. Oughton disclosed no relevant financial relationships.

A version of this article first appeared on


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