Introduction
coronavirus disease 2019
CORONAVIRUS, VIRUS, CORONAVIRUS DISEASE 2019, SEVERE ACUTE RESPIRATORY SYNDROME
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019 has caused extraordinary threats to human health. During the pandemic, SARS-CoV-2 has evolved into five variants of concern (VOCs), including Omicron the most antigenically divergent variant so far (To fight against the challenge of coronavirus disease 2019 (COVID-19) pandemic, various types of technologies have been applied concurrently in the development of COVID-19 vaccines, including inactivated, protein subunit, viral vector, or RNA-based platforms (In accordance with the guidance of WHO and Food and Drug Administration (FDA), a modified vaccine refers to a vaccine against a variant for which the mere change is the virus strain in an authorized prototype vaccine, aiming to improve the ability against SARS-CoV-2 variants (Sinovac has also developed an Omicron-adapted inactivated vaccine (Omicron vaccine) following the same manufacturing process as CoronaVac but containing Omicron BA.1 instead in early 2022. Here, we summarize the safety and immunogenicity results of this Omicron vaccine used as a booster dose from a phase III immuno-bridging clinical trial.