Abstract
Face masks do not completely prevent transmission of respiratory infections, but masked individuals are likely to inhale fewer infectious particles. If smaller infectious doses tend to yield milder infections, yet ultimately induce similar levels of immunity, then masking could reduce the prevalence of severe disease even if the total number of infections is unaffected. It has been suggested that this effect of masking is analogous to the pre-vaccination practice of variolation for smallpox, whereby susceptible individuals were intentionally infected with small doses of live virus (and often acquired immunity without severe disease). We present a simple epidemiological model in which mask-induced variolation causes milder infections, potentially with lower transmission rate and/or different duration. We derive relationships between the effectiveness of mask-induced variolation and important epidemiological metrics (the basic reproduction number and initial epidemic growth rate, and the peak prevalence, attack rate and equilibrium prevalence of severe infections). We illustrate our results using parameter estimates for the original SARS-CoV-2 wild-type virus, as well as the Alpha, Delta and Omicron variants. Our results suggest that if variolation is a genuine side-effect of masking, then the importance of face masks as a tool for reducing healthcare burdens from COVID-19 may be under-appreciated.
Keywords: COVID-19; SIR model; differential equations; face masks; infectious diseases; variolation.
【저자키워드】 COVID-19, Infectious diseases, Face masks, Differential equations, SIR model, variolation., 【초록키워드】 respiratory infections, SARS-CoV-2, Infectious diseases, Immunity, Infection, Delta, Transmission, omicron, variants, Mask, Prevalence, Epidemic, infections, attack rate, healthcare, Effectiveness, Face masks, basic reproduction number, epidemiological, acquired immunity, masking, estimate, Live virus, Face mask, dose, severe disease, infectious dose, growth rate, face, Metrics, Side-effect, Particles, growth, individual, severe infections, susceptible individuals, wild-type virus, smallpox, transmission rate, parameter, pre-vaccination, Prevent, initial, variolation, reducing, suggested, induce, cause, reduce, susceptible individual, 【제목키워드】 Transmission dynamics, face, Effect,