Severe acute respiratory syndrome coronavirus 2 Alpha and Beta variants became dominant in Finland in spring 2021 but had diminished by summer. We used phylogenetic clustering to identify sources of spreading. We found that outbreaks were mostly seeded by a few introductions, highlighting the importance of surveillance and prevention policies.
Keywords: Alpha variant; Beta variant; COVID-19; Finland; SARS-CoV-2; coronavirus disease; epidemiology; infectious disease transmission; phylogeny; public health surveillance; respiratory infections; severe acute respiratory syndrome coronavirus 2; vaccination; vaccines; viruses.