A study by HKUMed and CU Medicine shows that a third dose of Comirnaty vaccine given to those who received two doses of either Comirnaty or CoronaVac provides protective levels of antibody against the Omicron variant, while a third dose of CoronaVac does not. Two doses of either vaccine provide poor neutralising antibody responses against Omicron. Researchers urge people to get vaccinated and receive a third dose of Comirnaty around six months after their second dose for optimal protection.