Comparison of Omicron and Delta Variant Infection COVID-19 Cases - Guangdong Province, China, 2022.

What Is Already Known About This Topic?: The Omicron variant has been listed as a variant of concern, but the characteristics still remain unclear.

What Is Added By This Report?: The vaccinated proportion of 65 imported coronavirus disease 2019 cases that were infected with Omicron variant in this study was 89.23%, which was higher than Delta cases. Most imported cases infected with Omicron were tested positive using polymerase chain reaction after entering Guangdong within 3 days, a shorter period than Delta.

What Are The Implications For Public Health Practice?: Under this observation, the international travelers infected with Omicron variant were detected positive earlier after entry than those infected with Delta variant. Breakthrough infections occurred in most Omicron cases in this study, but vaccination was still effective to reduce the incidence of severe illness. Omicron surveillance should be strengthened.