Fisman and Tuite's timely evidence of the increasing virulence of SARS-CoV-2 variants is unlikely to convince the vaccine-hesitant to change their mind.1 It will increase the remorse felt by most unvaccinated victims of COVID-19. In June 2021, Public Health Ontario completed an excellent review of ring-vaccination as a strategy against COVID-19 and concluded that its application was premature.2 Experience in Canada and around the world shows coming waves of COVID-19 to be caused by, and to affect, the unvaccinated population. Ring-vaccination has been used successfully to suppress Ebola and Smallpox.3,4 It targets two groups: the recently infected, for whom vaccination is known as post-exposure prophylaxis (PEP), and their wide circle of unvaccinated contacts. We know the latter is safe as this was the strategy during the initial roll-out of the COVID-19 vaccine, where areas of high virus prevalence were targeted. PEP theoretically benefits the recently infected by converting their naive immune response, which is modified by the virus in patients who get severe or chronic COVID, into the type 1 immune response of the vaccinated, which eliminates the virus. If ring-vaccination is undertaken in a manner that gathers information, we would provide a vital service to the world. Fisman and Tuite's prediction of a more deadly wave due to variants of concern has already occurred in parts of Canada where release from lock-down was premature. Pressure to remove lock-down 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 unvaccinated patients with COVID-19.

Competing Interests:None declared.

References 

1. David N. Fisman, Ashleigh R. Tuite. Evaluation of the relative virulence of novel SARS-CoV-2 variants: a retrospective cohort study in Ontario, Canada. CMAJ 2021;10.1503/cmaj.211248.

2. Public Health Ontario. COVID-19 Vaccination for Post-Exposure Prophylaxis (PEP) or Ring Vaccination. 2021 Available: https://www.publichealthontario.ca/-/media/documents/ncov/covid-wwksf/2021/07/wwksf-vaccination-post-exposure-prophylaxis.pdf?sc_lang=en

3. Kretzschmar M, van den Hof S, Wallinga J, van Wijngaarden J. Ring vaccination and smallpox control. Emerg Infect Dis. 2004 May;10(5):832-41. doi: 10.3201/eid1005.030419. PMID: 15200816

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 Feb 4;389(10068):505-518.