Hong Kong Demonstrates Effective Use Of Covid Public Health Mitigation

(Posted on Wednesday, November 24, 2021)

It is clear from surging cases in Europe and in the US that we cannot make the mistake of relying on vaccines alone for population protection. We need to fight Covid fatigue and maintain the effective public health protocols of test, trace and isolate. Here, I describe a new study from Hong Kong that further validates this approach by demonstrating how effective stringent quarantine policies are in controlling Covid transmission without the need for city-wide lockdowns. Only 6 out of 4198 participants in the study tested positive for SARS-CoV-2 antibodies after three waves of Covid that occurred prior to Hong Kong’s vaccination rollout.

Despite a relatively slow vaccine uptake, Hong Kong is one of the few places that has successfully controlled Covid cases throughout each stage of the ongoing pandemic. Daily cases have never risen above 180 a day and the average daily case count in the wake of the Delta variant that has ravaged so many other places has been between two and eight cases. This is particularly impressive in a densely populated city such as Hong Kong. These results are thanks to rigorous contact tracing, targeted testing blitzes, and strict border controls and quarantines.

The Hong Kong study authors sought to discover whether there were some asymptomatic or otherwise unidentified cases that were not included in these low daily case counts and designed a study to assess the prevalence of unidentified SARS-CoV-2 infection. A prospective cross-sectional study was conducted in Hong Kong after each major wave of the Covid-19 pandemic (April 21 to July 7, 2020; September 29 to November 23, 2020; and January 15 to April 18, 2021). A total of 4198 Adults who had not been diagnosed with Covid-19 were recruited during each period, and their sociodemographic information, symptoms, travel, contact, quarantine, and Covid-19 testing history were collected. SARS-CoV-2 IgG antibodies were detected by an enzyme-linked immunosorbent assay based on spike (S1/S2) protein, followed by confirmation with a commercial electrochemiluminescence immunoassay based on the receptor-binding domain of spike protein. All participants were tested for SARS-CoV-2 IgG antibodies using an enzyme-linked immunosorbent assay based on spike (S1/S2) protein, followed by confirmation with a commercial electrochemiluminescence immunoassay based on the receptor-binding domain of spike protein.

Overall, 6 participants were confirmed to be positive for SARS-CoV-2 antibodies. Two participants with positive results were from the first recruitment, 1 from the second recruitment, and 3 from the third recruitment which corresponded to positivity rates of 0.22% (2 of 903), 0.10% (1 of 1046), and 0.13% (3 of 2249). The researchers used these percentages and applied a weighted adjustment according to the sex and age distribution of the general adult population in Hong Kong in order to estimate the number of unidentified SARS-CoV-2 infections.

The adjusted prevalence of unidentified infection was found to be at 0.15%, with fewer than 1.9 unidentified infections for every recorded case. The findings suggest that stringent isolation and quarantine policies even without complete city lockdown are very successful in minimizing SARS-CoV transmission.

Rigorous testing, tracing, and isolating is a highly effective Covid control policy that the US and many other countries have never fully embraced. As we continue to battle vaccine hesitancy and waning immunity in those who are vaccinated, our arsenal needs to include more than just medical defenses. The best strategy will combine the powers of medical and public health defenses to include vaccination with boosters as indicated, antiviral drugs, testing, tracing, quarantining, ventilation and masking when appropriate.

Read the full article on Forbes

Originally published on Forbes on November 24, 2021