Letters | Why Hong Kong’s 21-day quarantine policy seems unscientific

Readers question the scientific justification behind Hong Kong’s 21-day quarantine and discuss the pros and cons of a vaccine passport system

Reading Time:3 minutes

Isolation units at the Penny’s Bay Quarantine Centre on Lantau Island on December 16. Passengers who fly into Hong Kong from certain places deemed particularly high risk must undergo quarantine at the centre for four days before moving to a quarantine hotel. Photo: May Tse

Published: 7:30am, 4 Jan 2022

I don’t see much scientific justification to support the current 21-day quarantine policy mandated in Hong Kong. However, I would like to thank the powers that be for the opportunity to be required to spend 21 days in quarantine in Hong Kong.

This provided me with the chance to do some data analysis and the time to think this through. However, after reviewing the facts I collected, I couldn’t find any scientific evidence supporting the 21-day quarantine policy.

The Hong Kong government requires those entering the city from countries deemed “high risk” to undergo 21 days of quarantine in a hotel on a government list. This “high risk” list now includes almost every major country in the world. Those arriving from these “high risk” countries undergo PCR tests daily in quarantine for the first seven days.

According to Centre for Health Protection, the incubation period for this virus ranges “from one to 14 days, most commonly around five to six days”. We now know that the virus can spread – and therefore be identified by a test – before symptoms appear.

Given that a passenger to Hong Kong has taken one PCR test before and after the flight and assuming both results are negative, the most likely chance of an imported confirmed case is among passengers at the early stage of the incubation period. Therefore, I completely support performing more tests during the quarantine period to identify potential positive cases.

However, it seems there is little scientific reason for the government to enforce quarantine of more than 14 days since sufficient testing will be able to identify all the cases based on what we know about the virus.