2023-04-032023-04-032023-01-221999-4915http://hdl.handle.net/2133/25429The COVID-19 pandemic has lately been driven by Omicron. This work aimed to study the dynamics of SARS-CoV-2 Omicron lineages during the third and fourth waves of COVID-19 in Argentina. Molecular surveillance was performed on 3431 samples from Argentina, between EW44/2021 and EW31/2022. Sequencing, phylogenetic and phylodynamic analyses were performed. A differential dynamic between the Omicron waves was found. The third wave was associated with lineage BA.1, characterized by a high number of cases, very fast displacement of Delta, doubling times of 3.3 days and a low level of lineage diversity and clustering. In contrast, the fourth wave was longer but associated with a lower number of cases, initially caused by BA.2, and later by BA.4/BA.5, with doubling times of about 10 days. Several BA.2 and BA.4/BA.5 sublineages and introductions were detected, although very few clusters with a constrained geographical distribution were observed, suggesting limited transmission chains. The differential dynamic could be due to waning immunity and an increase in population gatherings in the BA.1 wave, and a boosted population (for vaccination or recent prior immunity for BA.1 infection) in the wave caused by BA2/BA.4/BA.5, which may have limited the establishment of the new lineages.application/pdf1-13engopenAccessSARS-CoV-2OmicronSouth AmericaBA.1BA.2BA.4BA.5publishedVersionTorres, CarolinaNabaes Jodar, MercedesAcuña, DoloresZambrana Montaño, Romina MicaelaCulasso, Andrés Carlos AlbertoAmadio, Ariel FernandoAulicino, PaulaCeballos, SantiagoCacciabue, MarcoDebat, HumbertoDus Santos, María JoséEberhardt, María FlorenciaEspul, CarlosFay, FabiánFernández; María AilénFernández, FrancoFernandez Muñoz, Juan ManuelFerrini, FlorenciaGallego, FernandoGiri, Adriana AngélicaCerri, AgustinaBolatti, Elisa MaríaGismondi, María InesGoya, StephanieGramundi, IvánIrazoqui, José MatíasKönig, Guido AlbertoLeiva, VivianaLucero, HoracioMarquez, NathalieNardi, CristinaOrtiz, BelénPianciola, LuisPintos, Carolina BeatrizPuebla, Andrea FabianaRastellini, Carolina VictoriaRojas, Alejandro EzequielSfalcin, JavierSuárez, ArielTittarelli, EstefaníaToro, RosanaVillanova, Gabriela VaninaZiehm, María CeciliaZimmermann, María CarlaZunino, SebastiánProyecto PAIS Working GroupValinotto, LauraViegas, MarianaUniversidad Nacional de RosarioAttribution 4.0 International (CC BY 4.0)