Reversed socioeconomic patterning of COVID-19 burden between infection waves in Hong Kong

Using individual-level characteristics of confirmed coronavirus disease 2019 (COVID-19) cases, the WHO Collaborating Centre for Infectious Disease Epidemiology and Control at The University of Hong Kong (HKU) has found a reversal of COVID-19’s socioeconomic burden pattern in the ethnically homogeneous population of Hong Kong through pandemic waves.

“Whereas many cases in the first two waves were imported, often by students or business travellers, infections shifted more towards local transmission in persons who were not economically active or did not have working from home [WFH] flexibility in the third wave,” reported the researchers.  [Eur J Hum Genet 2006;14:17-25]

As of 31 August 2020, a total of 4,811 COVID-19 cases had been laboratory-confirmed in Hong Kong, among which 3,556 (74 percent) were infected locally, while the remaining 1,255 cases were determined to have been acquired outside Hong Kong. The majority (86 percent) of cases in the third wave (n=3,773) were locally acquired. [Clin Infect Dis 2021;ciab002]

Information on occupation was available for 67 percent (n=3,238) of the cases, with no significant difference in the availability of occupation information among imported and local cases (p=0.12). The proportion of economically inactive individuals among confirmed cases in the first two waves and the third wave was remarkably similar (26.2 percent and 26.5 percent, respectively). The majority (82 percent) of imported cases in the first two waves were economically inactive individuals, including students studying overseas (79 percent), while the composition shifted towards production workers (23 percent; 79 percent of whom were foreign domestic helpers) and executives and professionals (22 percent; 79 percent were air or sea crew) in the third wave (p<0.01).

“Our results revealed that students, retirees and homemakers made up a considerable proportion of the COVID-19 cases in Hong Kong. These groups could have presumably stayed home more and were less constrained by work compared with those in formal employment. Our results suggested that transmission may also be associated with the infection risks of contacts, including visiting places with high risks of occurrences of case clusters [eg, dorms and restaurants for retirees]. In particular, we found that one in seven local cases in the third wave were retirees, one-third of whom were infected in nursing homes. Given their high infection fatality risk, it is important to enforce public health measures shielding older adults,” emphasized the researchers. [Nat Med 2020;26:506-510]

According to telephone surveys conducted with 3,594 adult Hong Kong residents between 26 May and 21 August 2020, executives and professionals (36 percent) experienced more WFH time (9.7 percent reported 40 hours WFH per week; p<0.01) compared with clerical and service and production workers.

“By the end of September 2020, Hong Kong had managed to suppress three epidemic waves of COVID-19 with a series of control measures targeting travellers and physical distancing in the local community. Our findings for the third wave suggest that people who were less sensitive to these control measures [eg, those who cannot WFH or are economically inactive] may face disproportionally higher risks of infection while maintaining essential services in the community. Therefore, contextual determinants should be taken into account in future policy planning aimed at mitigating such disparities,” concluded the researchers.