The development of the SARS-CoV-2 Omicron BA.2 substrain was exacerbated by low artificial immunity in Hong Kong.

Recent reports posted on Research Square* Preprint servers have shown that inadequate herd immunity exacerbated the development of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.2 substrain in Hong Kong.

Background

SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is known for its rapid human-to-human transmission, propensity to cause serious illness, and the production of variants that avoid herd immunity. It has been. Strict non-pharmaceutical COVID-19 measures imposed by countries around the world limit the spread of SARS-CoV-2, but these measures have undesired socio-economic and mental health implications. Bringing.

Predicting future COVID-19 wave intensities is an important part of developing a public health strategy. Tracking population defense immunity against SARS-CoV-2 variants conferred by COVID-19 or its vaccination may aid in the ability to estimate the effects of SARS-CoV-2 on public health systems. .. SARS-CoV-2 serum monitoring with neutralizing antibody (NAb) assessment is useful in determining the amount of protective immunity in the community.

A serum surveillance assessment in Hong Kong conducted by the authors of this study reported that less than 1% of serum samples obtained from the population prior to March 2021 were SARS-CoV-2 positive. Nevertheless, the COVID-19 seroprevalence is a hike from April 2021.

About research

In the current serum surveillance study, scientists used the Surrogate Virus Neutralization Test (sVNT) to raise for COVID-19 positivity between January and December 2021 at Queen Mary Hospital in Hong Kong. We profiled 1800 serum samples recovered from the Clinical Biochemistry Institute. sVNT was strongly correlated with the conventional live virus neutralization test (cVNT) for SARS-COV-2 ancestral strains.

In addition, SARS-CoV-2 positive serum samples from sVNT were further analyzed using cVNT to evaluate NAb titers for SARS-CoV-2 ancestors and Omicron BA.2 and BA.1 substrains. The authors currently monitor serum using genomic and epidemiological data from the fifth SARS-CoV-2 wave in Hong Kong, which exceeded 1 million COVID-19 patients by March 18, 2022. I evaluated the findings.

Researchers collected approximately the same number of anonymized serum samples, depending on their availability from a cohort of 10 years each, from 0 to 9 to 80 years and older. A total of 300 serum samples were selected and randomly tested every two months from January / February 2021 to November / December 2021. Specimens with insufficient serum volume were excluded from the analysis.

Results and discussion

The study found that only 30% of the study population had SARS-CoV-2 positive sVNT, even though the COVID-19 cumulative double vaccination coverage in Hong Kong exceeded 60% by November 2021. I showed that I was there. In addition, NAb titers for SARS-CoV-2 Omicron BA.2 and BA.1 sublineage were detected only at 7.3% and 2.3%, respectively.

The sVNT results showed that SARS-CoV-2 seroprevalence was significantly similar to the cumulative double vaccination rate of COVID-19 in cohorts aged 20-29 and 10-19 years. In the elderly, on the other hand, there is a significant difference between SARS-CoV-2 vaccination and sVNT seroprevalence, which researchers believe is due to the low immune response of this age group.

Another factor affecting the low SARS-CoV-2 seroprevalence in the elderly was the preference for the COVID-19 vaccine. More than half of the study population over the age of 60 chose the CoronaVac vaccine. CoronaVac recipients reported lower seroprevalence than BNT162b2 recipients in direct analysis. In addition, CoronaVac vaccinated patients had a faster seroprevalence than BNT162b2 recipients. These findings support the World Health Organization’s advice that older people should receive three CoronaVac doses.

Elderly people showed the lowest percentage of COVID-19 protective immunity. No one in the 80+ age group has SARS-CoV-2 positive sVNT, and only 12% of the 70-79 year cohort have a detectable NAb titer for BA.2 or BA. Had .1. In addition, none of the participants in the age category over 70 had a detectable NAb titer for Omicron BA.2 or BA.1 sublineage. The case fatality rate in the cohort over 80 years was 9.2% in the 5th SARS-CoV-2 wave in Hong Kong.

The incidence of SARS-CoV-2 in Hong Kong was very low due to the elimination strategy, so the NAb titers detected by either cVNT or sVNT in most subjects were COVID-19 vaccination rather than viral infection. May have been triggered by. As expected, serum samples from the cohort aged 0-9 years were not SARS-CoV-2 positive in sVNT, as COVID-19 vaccination in this group was not initiated in Hong Kong during the study period.

The seroprevalence declined in November / December 2021 and the vaccination rate after September, indicating that the vaccine’s protective effect on SARS-COV-2 was weakened. In addition, the BA.2 NAb titer was usually higher than the subject’s BA.1 NAb titer.

Overall, the lack of protective immunity against the Omicron BA.2 substrain, especially among the elderly, probably contributed to Hong Kong’s devastating fifth COVID-19 wave, expanding rapidly in February 2022, Overwhelmed the medical system.

Conclusion

The results of the study showed that older people were significantly less likely to be NAb seropositive for their ancestral SARS-CoV-2 sequence than younger people. The seroprevalence of NAb increases in conjunction with vaccine intake in the general population. Still, older people have a NAb seroprevalence that is substantially lower than the vaccination rate.

In addition, the frequency of NAb serum positivity for SARS-CoV-2 omicron variants was much lower than for ancestral virus strains in all age categories. Case fatality rates for cohorts over the age of 80 were unusually high during the 5th COVID-19 wave in Hong Kong, where the Omicron BA.2 substrain was predominant.

Overall, this study means that in Hong Kong, the catastrophic outbreak of SARS-CoV-2 Omicron BA.2 was caused by a lack of protective immunity in the community, especially in the sensitive elderly population, and evolved. Continuous defensive immunosurveillance against SARS-CoV-2 mutants.

*Important Notices

Research Square publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information. ..