The rise and fall of Alpha and Beta variants of SARS-CoV2 in Finland in spring of 2021

Abstract Two SARS-CoV-2 Variants of Concern, Alpha (~ 80%) and Beta (~ 23%) rapidly became dominant in Finland in the spring of 2021 but diminished near summer. To assess their temporal epidemiological dynamics among Finnish cases, we began large-scale sequencing efforts to identify spreading events and sources via phylogenetic clustering analyses. The results show the majority belonged to clusters spreading in the community while few sequenced samples were singletons. The results highlight the importance of surveillance and preventative policies in controlling the epidemic.