Covid-19: study estimates 20,000 undetected infections in Hong Kong

An estimated 20,000 Hongkongers have had undetected coronavirus infections, a relatively low figure which shows the city’s anti-pandemic measures are working, according to a new study.

The year-long study launched in April 2020 by the Chinese University of Hong Kong (CUHK) tested 4,198 adults for Immunoglobulin G (IgG) antibody, a sign of previous infections, and six people were found to be carrying it.

CUHK study hidden Covid-19 — Professors Paul Chan (left) and Martin Wong (right) announcing the results. Photo: CUHK.

Extrapolating from this, the CUHK team estimated that around 0.3 per cent of the city’s population, around 20,000 people, had experienced undetected coronavirus infections.

Hong Kong has reported 11,837 Covid-19 cases and 210 deaths since the pandemic began over a year ago.

Martin Wong, professor at CUHK’s School of Public Health and Primary Care, said the ratio of hidden Covid-19 cases was “a very low proportion compared to overseas data,” and this showed that Hong Kong’s “containment and contact tracing measures are effective.”

The government extended current social distancing measures for another two weeks on Wednesday, meaning that public gatherings of more than four people are banned until at least June 9.

Carrie Lam observes vaccine administration at a vaccination community centre — Photo: GovHK

Another CUHK study showed both types of Covid-19 vaccine provided in Hong Kong, the Chinese-made Sinovac and Germany’s BioNTech, were able to provide protection. People who received both doses of either brand had successfully developed antibodies.

However, the city has had a relatively low take-up rate since the government’s free vaccination programme began in February. Around 1.29 million people or 20 percent of the total population had received a first dose as of Wednesday while some 934,300 of them had been fully vaccinated.

Air ticket lucky draw

The Hong Kong Airport Authority on Wednesday launched a lucky draw for 60,000 plane tickets for vaccinated Hong Kong residents and airport staff in an attempt to boost the rate.

According to the authority, 50,000 tickets will be given to the city’s residents, and 10,000 to airport staff, who had been vaccinated by the end of September.