Fisman and Tuite’s timely evidence of the increasing virulence of SARS-CoV-2 variants1 may increase the remorse felt by unvaccinated victims of COVID-19. Experience in Canada and around the world shows coming waves of SARS-CoV-2 infection to be caused by, and to affect, the unvaccinated population.
In June 2021, Public Health Ontario completed an excellent review of ring vaccination as a strategy against SARS-CoV-2 infection and concluded that its application was premature.2 Ring vaccination has been used successfully to suppress Ebola and smallpox.3,4 It targets 2 groups: people who are recently infected, for whom vaccination is known as postexposure prophylaxis (PEP), and their wide circle of unvaccinated contacts. This was essentially the strategy during the initial rollout of the SARS-CoV-2 vaccine, where areas of high virus prevalence were prioritized for vaccination. Theoretically, PEP benefits people who are recently infected by converting their naive immune response, which is modified by the virus in patients who develop severe or chronic COVID-19, into the type 1 immune response of people who are vaccinated, which eliminates the virus.
Fisman and Tuite’s prediction of a more deadly wave caused by variants of concern has already occurred in parts of Canada where release from lockdown was premature. Pressure to remove lockdown measures elsewhere will be irresistible soon. Now is the time to introduce a monitored ring-vaccination strategy, which may help relieve the remorse felt by people who are unvaccinated and have COVID-19.
Footnotes
Competing interests: None declared.
References
- 1.Fisman DN, Tuite AR. Evaluation of the relative virulence of novel SARS-CoV-2 variants: a retrospective cohort study in Ontario, Canada. CMAJ 2021;193:1619–25. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.COVID-19 vaccination for post-exposure prophylaxis (PEP) or ring vaccination. Toronto: Public Health Ontario; 2021. Available: https://www.publichealthontario.ca/-/media/documents/ncov/covid-wwksf/2021/07/wwksf-vaccination-post-exposure-prophylaxis.pdf?sc_lang=en (accessed 2021 Oct. 12). [Google Scholar]
- 3.Kretzschmar M, van den Hof S, Wallinga J, et al. Ring vaccination and smallpox control. Emerg Infect Dis 2004;10:832–41. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Henao-Restrepo AM, Camacho A, Longini IM, et al. Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ça Suffit!). Lancet 2017;389:505–18. [DOI] [PMC free article] [PubMed] [Google Scholar]