JMIR Publications

ABSTRACT

Background:

The coronavirus disease 2019 (COVID-19) Omicron BA.2 epidemic wave in Hong Kong peaked in the first quarter of 2022. Following implementation of stringent public health measures, the daily number of reported cases fell from over 50000 to below 2000. While outbreaks steadily receded, the government rolled out a 3-day “voluntary universal rapid testing” campaign to invite all citizens to self-perform daily rapid antigen test (RAT) to identify undetected prevalent infections.

Objective:

To evaluate the uptake and results of RAT mass screening to estimate the population’s residual epidemic burden and assess the risk of further transmission.

Methods:

A cross-sectional study comprising an open online population-based survey was conducted a week after the RAT campaign. Participants were asked to report their COVID-19 vaccination and infection history, RAT performance and test result during the period. They were also invited to report their co-living individuals’ test performance and results. Reasons for non-uptake were enquired. Testing and positive rates were age-adjusted. Determinants of undergoing RAT were identified using univariable and multivariable logistic regression models.

Results:

Totally, particulars from 21769 individuals were reported by 8338 participants. The overall age-adjusted testing rate was 74.94%, with over 80% participants in the age groups of 45-84 years old having self-performed RAT during the campaign period. After age-adjustment, 1.03% participants tested positive. The positive rates in age groups between 20 and 29 years, and above 84 years exceeded 2%. Taking into account the positive rate and 5819 reported cases during the period, the cases identified in the campaign might account for at most 9.14% of all infections. Testers were more likely to be female, older, not previously diagnosed with COVID-19, and have received COVID-19 vaccination. Adjusting for the number of household members, those living with a child aged under 12 years and whose household members were also tested were more likely to have self-performed an RAT. Main reasons for not getting RAT tested included absence of symptoms (54%), disbelief of the appropriateness of the campaign as an anti-epidemic measure (32%), and recent COVID-19 diagnosis (30%).

Conclusions:

Despite clear evidence of receding epidemic wave, the residual population burden remained substantial. The high participation rate in mass screening indicated that the voluntary RAT was well accepted by the general population, making it a feasible option for implementation as a complementary means of public health surveillance.