This study investigates the effectiveness of unvaccinated-only screening programs for mitigating SARS-CoV-2 spread in populations with varying vaccination rates. Using a model of SARS-CoV-2 transmission, the researchers explored different scenarios involving transmission rates, vaccine effectiveness, prior infection rates, and screening programs. They found that as vaccination rates increase, the proportion of transmission driven by unvaccinated individuals decreases. Once vaccine coverage exceeds 55% (Omicron) or 80% (Delta), most community spread is driven by vaccine breakthrough infections. The effectiveness of unvaccinated-only screening decreases with increasing vaccination rates, falling into three categories of impact on infections and hospitalizations. The study highlights the dependence of effective unvaccinated-only screening on population immunity, vaccination rates, and the specific variant.

Kate M. Bubar, Casey E. Middleton, Kristen K. Bjorkman, Roy Parker, Daniel B. Larremore