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The epidemiological options of SARS-CoV-2 infections within the fifth wave in Hong Kong

A current report posted to the medRxiv* preprint server introduced the epidemiology of the extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.2 sublineage infections in Hong Kong.

Study: Epidemiology of infections with SARS-CoV-2 Omicron BA.2 variant in Hong Kong, January-March 2022. Image Credit: Yung Chi Wai Derek/Shutterstock
Examine: Epidemiology of infections with SARS-CoV-2 Omicron BA.2 variant in Hong Kong, January-March 2022. Picture Credit score: Yung Chi Wai Derek/Shutterstock


Following the emergence of the SARS-CoV-2 authentic pressure in early 2020, many SARS-CoV-2 variants of concern have led to huge outbreaks and important deaths. The SARS-CoV-2 Omicron variant first detected in South Africa and Botswana in late November 2021 is the newest SARS-CoV-2 variant to unfold internationally.

Within the first two years of the coronavirus illness 2019 (COVID-19) pandemic, Hong Kong recorded 12,631 confirmed SARS-CoV-2 instances and 213 SARS-CoV-2-associated mortality. By December 31, 2021, 70% of Hong Kong residents had obtained two doses of COVID-19 vaccination. But, in early 2022, Hong Kong noticed an enormous COVID-19 wave, primarily pushed by the SARS-CoV-2 Omicron BA.2.2 variant, with greater than 1.1 million reported SARS-CoV-2 infections and over 7900 deaths.

In regards to the research

Within the current research, the scientists profiled the epidemiological traits of the SARS-CoV-2 infections within the COVID-19 pandemic’s fifth wave (January to March 2022) in Hong Kong. 

The authors estimated the incubation interval of 80 people contaminated with the SARS-CoV-2 Omicron variant with recognized symptom onset and publicity through the fifth COVID-19 wave in Hong Kong. The crew assessed the serial interval of COVID-19 utilizing particulars of 43 symptomatic SARS-CoV-2 infectors to infectee pairs. Additional, the Omicron BA.1 variant technology time was computed using datasets from 45 infector-infectee pairings with outlined exposure-to an infection time. As well as, the serial interval and technology time distributions of the Omicron variant have been assessed utilizing the Weibull distribution.

The crew stratified COVID-19 instances as vaccinated with major collection SARS-CoV-2 vaccines if sufferers had obtained two photographs of the inactivated CoronaVac or messenger ribonucleic acid (mRNA) BNT162b2 vaccine, with a most up-to-date dose round two weeks prior. The researchers predicted that the age-specific case-fatality-risk (CFR) with out completion of the principle collection of immunization within the fifth COVID-19 wave was much like these verified within the SARS-CoV-2 pandemic one to 4 waves all through all age teams after adjusting for unresolved outcomes in sure folks.


The research outcomes demonstrated that the SARS-CoV-2 Omicron BA.2.2 variant unfold swiftly with a doubling time of three.4 days in Hong Kong, quickly exceeding test-and-trace, isolation, and quarantine capability, leading to a big variety of COVID-19 sufferers in want of hospitalization with restricted assets. This was regardless of strict public well being and social precautions. The comparatively shorter technology time and serial interval of the Omicron BA.2 sublineage relative to the prior SARS-CoV-2 variants and the improved inherent transmissibility led to the speedy viral unfold within the inhabitants.

The drastic COVID-19-linked deaths in Hong Kong through the fifth wave might be ascribed to the speedy unfold of an infection and low vaccination protection amongst older individuals. Whereas complete vaccine protection was 70% firstly of the fifth wave, solely 50% and 20% of these aged ≥65 and ≥80 years had accomplished the principle collection of vaccinations, respectively. As much as March 23, 2021, 92.5% of all SARS-CoV-2-related deaths with age recorded occurred in these aged ≥65 years and 70.8% in folks aged ≥80.

Within the early portion of the fifth wave, the researchers found an equivalent fatality danger for unvaccinated COVID-19 sufferers relative to prior waves, implying that BA.2’s inherent severity is probably not considerably decrease than the unique SARS-CoV-2 pressure. As well as, the authors reported that Omicron BA.2 an infection in folks aged 65-79 years or above 80 years with a whole major vaccination standing had a significantly lowered chance of loss of life.

Given the lack of expertise on the kind of SARS-CoV-2 variant for all particular person instances and the likelihood {that a} small variety of COVID-19 instances, together with mortality from clusters of the SARS-CoV-2 Delta infections, have been included within the research, the current CFR estimates might fractionally overestimate the fatality danger of Omicron in Hong Kong.


The research findings urged that the SARS-CoV-2 Omicron BA.2.2 pressure harbored a shorter technology time, incubation interval, and serial interval than different viral variants. In Hong Kong, the Omicron variants, notably the BA.2 sublineage, have been proven to have a superior transmission potential. People with an incomplete major vaccination routine, when contaminated with Omicron, skilled an equal mortality danger as those that received contaminated with the SARS-CoV-2 ancestral pressure within the prior COVID-19 pandemic waves.

Total, the current knowledge underscored the necessity for top SARS-CoV-2 vaccination protection, significantly amongst older individuals, and the need to reevaluate public well being and social methods in epidemic administration in response to a considerably transmissible viral variant sooner or later.

*Necessary discover

medRxiv publishes preliminary scientific stories that aren’t peer-reviewed and, subsequently, shouldn’t be considered conclusive, information medical observe/health-related conduct, or handled as established info.


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