SARS-CoV-2 Omicron: What’s New in Evidence ?

The Omicron variant of SARS-CoV-2 demonstrated significantly higher transmissibility than Delta, with shorter generation times and greater secondary attack rates. While it caused less severe disease overall—including lower hospitalization and ICU rates—evidence showed Omicron had a higher reinfection risk, even among vaccinated individuals. Vaccine effectiveness against Omicron waned over time, but booster doses restored protection. Preliminary data suggest the BA.2 subvariant may be more transmissible than BA.1, although vaccine effectiveness appears similar. Further evidence is needed to fully assess emerging Omicron sublineages.