Elsevier created a free COVID-19 resource centre in January 2020, offering information in English and Mandarin. The centre is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories. The Omicron variant of SARS-CoV-2 was identified in late 2021, emerging in a world weary of the pandemic. It is the fifth variant of concern (VoC) and has emerged as the dominant variant in many countries. Previous VoCs, such as alpha, beta, and delta, were associated with increased transmission and reinfection. Omicron has several mutations, including those that may increase transmissibility and immune escape. These mutations overlap with those in previous VoCs, suggesting potential for higher transmissibility and immune evasion. Early data suggest that Omicron may spread more rapidly than previous variants, particularly due to mutations near the furin cleavage site. Cases in South Africa increased rapidly, and PCR tests with S-gene target failure also rose. However, it is not yet clear whether Omicron is more transmissible than delta. Clinical data from South Africa indicate that Omicron may affect younger individuals with a clinical presentation similar to past variants. Although no alarming clinical concerns have been raised, the data should be interpreted cautiously. Immune escape is a concern, as Omicron may evade vaccine protection. However, most vaccines remain effective in preventing severe disease, hospitalization, and death. Observational studies show high vaccine efficacy in preventing severe disease, even up to six months after vaccination. Diagnostics and treatments for Omicron are likely effective, with the exception of monoclonal antibodies, for which data are not yet available. Public health measures, such as mask-wearing and hand hygiene, remain effective against Omicron. In conclusion, Omicron may spread more rapidly and escape antibodies more readily than previous variants, increasing the risk of reinfection and mild breakthrough infections. However, vaccination combined with public health measures remains an effective strategy to control the pandemic.Elsevier created a free COVID-19 resource centre in January 2020, offering information in English and Mandarin. The centre is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories. The Omicron variant of SARS-CoV-2 was identified in late 2021, emerging in a world weary of the pandemic. It is the fifth variant of concern (VoC) and has emerged as the dominant variant in many countries. Previous VoCs, such as alpha, beta, and delta, were associated with increased transmission and reinfection. Omicron has several mutations, including those that may increase transmissibility and immune escape. These mutations overlap with those in previous VoCs, suggesting potential for higher transmissibility and immune evasion. Early data suggest that Omicron may spread more rapidly than previous variants, particularly due to mutations near the furin cleavage site. Cases in South Africa increased rapidly, and PCR tests with S-gene target failure also rose. However, it is not yet clear whether Omicron is more transmissible than delta. Clinical data from South Africa indicate that Omicron may affect younger individuals with a clinical presentation similar to past variants. Although no alarming clinical concerns have been raised, the data should be interpreted cautiously. Immune escape is a concern, as Omicron may evade vaccine protection. However, most vaccines remain effective in preventing severe disease, hospitalization, and death. Observational studies show high vaccine efficacy in preventing severe disease, even up to six months after vaccination. Diagnostics and treatments for Omicron are likely effective, with the exception of monoclonal antibodies, for which data are not yet available. Public health measures, such as mask-wearing and hand hygiene, remain effective against Omicron. In conclusion, Omicron may spread more rapidly and escape antibodies more readily than previous variants, increasing the risk of reinfection and mild breakthrough infections. However, vaccination combined with public health measures remains an effective strategy to control the pandemic.