"The fact that HK’s daily reported cases have remained static around 300 for the past couple of weeks implies an Rt(real-time effective reproductive number)of 1 - ie we are on the cusp of a potential sixth wave if things tilt in the wrong direction slightly," according to Leung's Twitter post on Saturday.

It was reported that Leung said in an internal web conference held by the Faculty of Medicine that his data model suggested the sixth wave of the pandemic could come in two weeks.

The faculty generated via a mathematical model in March that if the city gradually relaxed social distance measures according to the roadmap, the sixth wave of the Covid-19 pandemic may emerge in early June.

They predicted the outbreak would last for about two months, during which another 2.21 million would be infected and 1,540 would die. However, the number of patients admitted to the hospital would be within the capacity of public health care.

Leung added on Twitter on Sunday that vaccines protect against serious complications and death, but do not work nearly as well against infection.

Even after the vaccination rate reached 100 percent, infected individuals may still carry the virus into the hospital, where it can be transmitted to the elderly, organ transplant recipients and other vulnerable groups.