SARS-CoV-2 Herd Immunity of the Kyrgyz Population in 2021

2021 ◽  
Author(s):  
Anna Y. Popova ◽  
Omor T. Kasymov ◽  
Vyacheslav Y. Smolenski ◽  
Вячеслав Смирнов ◽  
Svetlana A. Egorova ◽  
...  
Keyword(s):  
Randomized Study ◽  
Herd Immunity ◽  
Statistical Processing ◽  
Cloud Service ◽  
Asymptomatic Infection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Pasteur Institute ◽  
Cross Sectional ◽  
Saint Petersburg ◽  
Kyrgyz Population

Abstract Background. In the fight against coronavirus infection, an important direction is control of herd immunity to the pathogen. SARS-CoV-2 herd immunity is formed naturally as a result of manifest or asymptomatic infection, or artificially as a result of vaccination Aim: To assess the SARS-CoV-2 herd immunity status of the Kyrgyz population. Materials and methods. A cross-sectional, randomized study of SARS-CoV-2 herd immunity was carried out according to a program developed by Rospotrebnadzor, with the participation of the Saint Petersburg Pasteur Institute, taking into account WHO recommendations. In all study stages cloud service (internet) technologies were used. The ethics committees of the Preventive Medicine Association (Kyrgyzstan) and the Saint Petersburg Pasteur Institute (Russia) approved the study. A total of 9,471 volunteers were selected, representing 0.15% (95% CI 0.14-0.15) of the total population. They were randomized according to age and region. Antibodies (Abs) to the nucleocapsid antigen (Nag) were determined by enzyme-linked immunosorbent assay (ELISA) of volunteer blood plasma. For vaccinated individuals, Abs to the SARS-CoV-2 receptor-binding domain antigen (RBDag) were determined. Statistical processing of the results was carried out using Excel 2010 and other programs. Differences were designated as statistically significant at p<0.05. Results. The seroprevalence of the general population was 48.7% (95% CI 47.7-49.7), with a maximum in the group of '60-69 year old' (59.2% (56.6-61.7)) and a minimum in the group '1-17 y.o.' (32.7% (95 CI 29.4-36.1)). The largest proportion seropositive was found in the Chui region (51.3% (95% CI 47.9-54.8)). The lowest was in Osh city (38.1% (95 CI 32.6-43.9)). The maximum seropositivity was detected among healthcare workers (57.1% (95% CI 55.4-58.8); the minimum was noted among artists (38.6% (95% CI 26.0-52.4)). Asymptomatic SARS-CoV-2 positivity was 79.1% (96% CI 77.9-80.3). Vaccination with Sputnik V, EpiVacCorona, or Sinopharm formed comparable levels of immunity. Conclusions. The herd immunity to SARS-CoV-2 Nag is 48.75% (95% CI 47.7-49.7), and the overall immunity (Nag + RBDag) is 57%.

scholarly journals SARS-CoV-2 IgG Antibodies Seroprevalence and Sera Neutralizing Activity in MEXICO: A National Cross-Sectional Study during 2020

2021 ◽  
Vol 9 (4) ◽  
pp. 850
Author(s):  
José Esteban Muñoz-Medina ◽  
Concepción Grajales-Muñiz ◽  
Angel Gustavo Salas-Lais ◽  
Larissa Fernandes-Matano ◽  
Constantino López-Macías ◽  
...  
Keyword(s):  
Immunosorbent Assay ◽  
Neutralizing Antibodies ◽  
Herd Immunity ◽  
Cross Sectional Study ◽  
Molecular Techniques ◽  
Diagnostic Methods ◽  
Molecular Diagnostic ◽  
Enzyme Linked Immunosorbent Assay ◽  
Cross Sectional ◽  
Neutralizing Activity

Until recently, the incidence of COVID-19 was primarily estimated using molecular diagnostic methods. However, the number of cases is vastly underreported using these methods. Seroprevalence studies estimate cumulative infection incidences and allow monitoring of transmission dynamics, and the presence of neutralizing antibodies in the population. In February 2020, the Mexican Social Security Institute began conducting anonymous unrelated sampling of residual sera from specimens across the country, excluding patients with fever within the previous two weeks and/or patients with an acute respiratory infection. Sampling was carried out weekly and began 17 days before Mexico’s first officially confirmed case. The 24,273 sera obtained were analyzed by chemiluminescent-linked immunosorbent assay (CLIA) IgG S1/S2 and, later, positive cases using this technique were also analyzed to determine the rate of neutralization using the enzyme-linked immunosorbent assay (ELISA). We identified 40 CLIA IgG positive cases before the first official report of SARS-CoV-2 infection in Mexico. The national seroprevalence was 3.5% in February and 33.5% in December. Neutralizing activity among IgG positives patients during overall study period was 86.1%. The extent of the SARS-CoV-2 infection in Mexico is 21 times higher than that reported by molecular techniques. Although the general population is still far from achieving herd immunity, epidemiological indicators should be re-estimated based on serological studies of this type.

scholarly journals Herd immunity to SARS-COV-2 in the population of the Southern regions of the Far East of Russia

2021 ◽  
Vol 6 (5) ◽  
pp. 253-273
Author(s):  
A. Yu. Popova ◽  
V. S. Smirnov ◽  
E. B. Ezhlova ◽  
A. A. Melnikova ◽  
O. E. Trotsenko ◽  
...  
Keyword(s):  
Statistical Significance ◽  
Herd Immunity ◽  
Far East ◽  
Amur Region ◽  
Reproductive Number ◽  
Pasteur Institute ◽  
Scientific Center ◽  
Cross Sectional ◽  
Population Immunity ◽  
The Far East

The aim: to study the structure and dynamics of population immunity to SARSCoV-2 of the population of the Southern Regions of the Far East (SRFE): Khabarovsk, Primorsky Krai and Amur Region during the COVID-19 epidemic in 2020.Materials and methods. The work was carried out according to the program for assessing population immunity to SARS -CoV-2 of the population of the Russian Federation according to the methodology developed by the Rospotrebnadzor with the  participation of the St.  Petersburg Pasteur Institute. The study was approved by  the  ethical committee of the St.  Petersburg Pasteur Institute. The selection of participants was carried out by a questionnaire method using cloud technologies. The  volunteers were randomized by age by stratification into 7  age groups: 1–17, 18–29, 30–39, 40–49, 50–59, 60–69, 70+ years old. Territorial randomization consisted in limiting the engaging of volunteers – no more than 30 people from one enterprise. After the initial cross-sectional study, a 3-stage seromonitoring was carried out, in which the same volunteers participated. Antibodies to the SARS-CoV-2 nucleocapsid were determined in peripheral blood serum by the enzyme immunoassay using an appropriate set of reagents produced by the State Scientific Center for Medical and Biological Sciences of the Rospotrebnadzor (Obolensk). Statistical analysis was performed using the Excel package. The confidence interval for the proportion was calculated using the A. Wald, J. Wolfowitz method with A. Agresti, B.A. Coull’s correction. The statistical significance of the differences was calculated online using a specialized calculator. The statistical significance of the differences was assessed with a probability of p˂ 0.05, unless otherwise indicated.Results. In a comparative analysis, the highest morbidity was observed in the Khabarovsk Territory, the lowest – in the Primorsky Territory. The level of seroprevalence among the population of the region was 19.6 % (95 % CI: 18.2–21.1) in  the  Khabarovsk Territory, 19.6  % (95  %  CI: 18.1–21.2) in the Primorsky Territory19,6 % and 45,5 % (95 % CI: 43.7–47.3) in the Amur region. The highest seroprevalence was noted among 1–17 years old children, mainly due to the subgroup of 14–17-years-olds. The smallest proportion of seropositive was found among 40–49-year-olds in the Khabarovsk Territory (14.7 %, 95 % CI: 11.2–18.6), 18–28-yearolds in the Primorsky Territory (13.3 %, 95 % CI: 10.0–17.1) and 30–39-year-olds in the Amur Region (36.3  %, 95%  CI:  31.7–41.6). No statistically significant dependence of  seroprevalence on territorial and occupational factors has been established, with the exception of an increase in the proportion of seropositive medical workers in Primorsky Territory. In the process of 3-stage seromonitoring, a regular increase in the proportion of seropositive people was revealed in all SRFE. The resulting tendency is correctly described by a second-order polynomial. A relationship was revealed between the number of convalescents and persons in contact with them, which made it possible to calculate the base reproductive number (R0) in the range from 1.4 (Primorsky Territory) to 2.4 (Amur Region). Analysis of seroprevalent volunteers showed that the number of asymptomatic individuals varied from 94.1 % (95 % CI: 92.8–95.3) to 98.3 % (95 % CI: 98.8–99.2). This indicates that most of the volunteers had COVID-19 asymptomatically.Conclusions. A comparative study showed the prevalence of seroprevalence in the Amur Region compared with the Khabarovsk and Primorsky Territories. The relationship between the number of convalescents and persons in contact with them was noted. The value of the base R0 is calculated. It has been shown that more than 90 % of seropositive individuals in the COVID-10 SRFE were asymptomatic.

scholarly journals Validation of a SARS-CoV-2 spike protein ELISA for use in contact investigations and sero-surveillance

2020 ◽  
Author(s):  
Brandi Freeman ◽  
Sandra Lester ◽  
Lisa Mills ◽  
Mohammad Ata Ur Rasheed ◽  
Stefany Moye ◽  
...  
Keyword(s):  
Disease Burden ◽  
Large Scale ◽  
Case Fatality ◽  
Asymptomatic Infection ◽  
Cross Reactivity ◽  
Spike Protein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Specific Enzyme ◽  
Cross Sectional ◽  
Contact Investigations

AbstractSince emergence of SARS-CoV-2 in late 2019, there has been a critical need to understand prevalence, transmission patterns, to calculate the burden of disease and case fatality rates. Molecular diagnostics, the gold standard for identifying viremic cases, are not ideal for determining true case counts and rates of asymptomatic infection. Serological detection of SARS-CoV-2 specific antibodies can contribute to filling these knowledge gaps. In this study, we describe optimization and validation of a SARS-CoV-2-specific-enzyme linked immunosorbent assay (ELISA) using the prefusion-stabilized form of the spike protein [1]. We performed receiver operator characteristic (ROC) analyses to define the specificities and sensitivities of the optimized assay and examined cross reactivity with immune sera from persons confirmed to have had infections with other coronaviruses. These assays will be used to perform contact investigations and to conduct large-scale, cross sectional surveillance to define disease burden in the population.

scholarly journals Factors associated with asymptomatic infection in family members and neighbors of patients with visceral leishmaniasis

2012 ◽  
Vol 28 (12) ◽  
pp. 2306-2314 ◽  
Author(s):  
Germano Silva Moura ◽  
Alcione Miranda dos Santos ◽  
Dorlene Maria Cardoso de Aquino ◽  
Antônio Augusto Moura da Silva ◽  
Arlene de Jesus Mendes Caldas
Keyword(s):  
Visceral Leishmaniasis ◽  
Index Case ◽  
Family Members ◽  
Cross Sectional Study ◽  
Asymptomatic Infection ◽  
Control Measures ◽  
Enzyme Linked Immunosorbent Assay ◽  
Cross Sectional ◽  
Factors Associated ◽  
Increased Risk

This study analyzed factors associated with asymptomatic Leishmania chagasi infection in family members and neighbors of patients with visceral leishmaniasis (VL). A cross-sectional study was conducted with 361 individuals in the counties comprising Ilha de São Luís (São Luís Island) in Maranhão State, Brazil. The Montenegro skin test (MST) and serology by enzyme-linked immunosorbent assay (ELISA) were performed to detect infection. Odds ratios (OR) and prevalence ratios (PR) and their 95% confidence intervals (95%CI) were estimated by multilevel logistic regression and Poisson regression, respectively. The rates of positive reactions were 71.3% for MST and 9.7% for ELISA. The variable associated with infection according to MST was living in the same household as the index case (PR = 1.36; 95%CI: 1.03-1.78). According to ELISA, the statistically significant variables were: living in the county of Raposa (OR = 3.56; 95%CI: 1.24-10.19) and living in the same household as the index case (OR = 2.70; 95%CI: 1.19-6.08). Family members of individuals with LV are at increased risk of infection. Priority control measures should target these families.

scholarly journals Seroprevalence of SARS-CoV-2 Antibodies in Symptomatic Individuals Is Higher than in Persons Who Are at Increased Risk Exposure: The Results of the Single-Center, Prospective, Cross-Sectional Study

Vaccines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 627
Author(s):  
Alexandr Zurochka ◽  
Maria Dobrinina ◽  
Vladimir Zurochka ◽  
Desheng Hu ◽  
Alexandr Solovyev ◽  
...  
Keyword(s):  
High Risk ◽  
Risk Group ◽  
Herd Immunity ◽  
Cross Sectional Study ◽  
High Risk Group ◽  
Enzyme Linked Immunosorbent Assay ◽  
Cross Sectional ◽  
Seropositivity Rate ◽  
Symptomatic Group ◽  
Increased Risk

The present study aimed to assess antibody seropositivity prevalence among symptomatic individuals and individuals with a high risk of occupational exposure to SARS-CoV-2. Participants from Chelyabinsk (Russian Federation) who were at an increased risk of exposure to SARS-CoV-2 (high-risk group, n = 1091) and participants who either had symptoms consistent with COVID-19 or were suspected to have experienced COVID-19 in the past (symptomatic group, n = 692) were enrolled between 28 September and 30 December 2020. Blood samples were tested by enzyme-linked immunosorbent assay D-5501 SARS-Cov-2-IgG-EIA-BEST and D-5502 SARS-Cov-2-IgM-EIA-BEST (AO Vector-Best, Novosibirsk, Russia). The overall seropositivity rate was 28.33–28.53%. SARS-CoV-2 antibodies were detected in 17.23% (adjusted prevalence of 17.17–17.29%) of participants in the high-risk and 45.95% (adjusted prevalence of 45.91–46.24%) in the symptomatic group. Higher IgG and IgM titers were observed in women compared to men, as well as in participants in the symptomatic group compared to those in the high-risk group. The results indicate that the seroprevalence among residents in several Russian regions is low (28.38%) and inadequate to provide herd immunity. The lower seroprevalence among participants in the high-risk group may be attributed to the enforcement of healthcare protocols and the use of adequate personal protective equipment.

scholarly journals Herd immunity to SARS-CoV-2 among the population of the Republic of Belarus amid the COVID-19 pandemic

2021 ◽  
Vol 11 (5) ◽  
pp. 887-904
Author(s):  
A. Yu. Popova ◽  
A. A. Tarasenko ◽  
V. Yu. Smolensky ◽  
S. A. Egorova ◽  
V. S. Smirnov ◽  
...  
Keyword(s):  
Herd Immunity ◽  
Age Groups ◽  
Statistical Processing ◽  
Threshold Level ◽  
Test System ◽  
Elisa Test ◽  
Surface Glycoprotein ◽  
Pasteur Institute ◽  
The Republic ◽  
Questionnaire Method

Objective was to investigate the SARS-CoV-2 collective immunity status of the population of Belarus within the context of the COVID-19 pandemic. Materials and methods. The work was carried out according to the methodology for assessing SARS-CoV-2 population immunity, developed by Rospotrebnadzor Russia and the Ministry of Health of Belarus with the participation of the St. Petersburg Pasteur Institute, taking into account WHO recommendations. The Bioethics Committee of Belarus and the local ethics committee of the St. Petersburg Pasteur Institute approved the study. Selection of participants was carried out using a questionnaire method and online technology (internet, cloud server). Volunteers were randomized into seven age groups (years of age): 1–17; 18–29; 30–39; 40–49; 50–59; 60–69; and 70+. Regional randomization ensured proportional representation of volunteers from each region, and no more than 30 people were included from one enterprise. In accordance with manufacturer instructions, blood plasma samples were analyzed for: IgG antibodies (Abs) to the SARS-CoV-2 nucleocapsid (Nc) using a quantitative ELISA test system; and IgG Abs to the receptor binding domain (RBD) of the SARS-CoV-2 S (spike) surface glycoprotein using a qualitative ELISA test system. Statistical processing was carried out using Excel 2010 and other software. Statistical differences were designated as significant when p < 0.05, unless otherwise indicated. Results. The level of seroprevalence, in terms of Abs to Nc among the Belarusian population, was 38.4% (95% CI 37.6–45.4). The highest Ab levels were found among individuals in older age groups (50-70+ years old). The lowest were found in children 1–17 years old and in young people 18–39 years old The distribution of seroprevalence across Belarusian regions was relatively homogeneous, with the exception of the Minsk Region, where a statistically significant decrease in the indicator was noted. In terms of profession, the largest share of seropositive individuals was found among transportation workers; the smallest was found in business. The moderate COVID-19 incidence has not led to a dramatic increase in the number of contacts. The base reproduction number (R0) was 1.3. In the Republic of Belarus, there was a moderate level of asymptomatic COVID-19 among seropositive individuals (45.3% [95% CI 44.0–46.7]). This form of infection was observed most often among children aged 1–17 years old (65.0% [95% CI 61.3–68.6]). In parallel with seroprevalence assessment, SARS-CoV-2 vaccination was carried out. We used two vaccines: Gam-COVID-Vac (also known as Sputnik V, developed by Gamaleya National Center for Epidemiology and Microbiology, Russia); and BBIBP-CorV (Sinopharm, PRC). Vaccination against SARS-CoV-2 was accompanied by an increase in the level of anti-RBD Abs (95% [95% CI 94.7–96.7]). Taking into account the vaccination of a subset of the population with BBIBP-CorV, the overall herd immunity, inferred from the analyzed indicators (presence of anti-Nc or anti-RBD Abs), was 47.1% (95% CI 46.3–48.0). Conclusion. COVID-19 in Belarus was characterized by a moderately pronounced course of the epidemic process. The threshold level of herd immunity to SARS-CoV-2 has not yet been reached, as a result of which the conditions for progression of the epidemic remain.

scholarly journals Herd immunity to SARS-CoV-2 in the Novosibirsk Region population amid the COVID-19 pandemic

2021 ◽  
Vol 66 (4) ◽  
pp. 299-309
Author(s):  
A. Yu. Popova ◽  
V. S. Smirnov ◽  
E. B. Ezhlova ◽  
A. A. Mel’nikova ◽  
L. V. Samoilova ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Herd Immunity ◽  
Threshold Level ◽  
Igg Antibodies ◽  
Pasteur Institute ◽  
Microsoft Excel ◽  
Cross Sectional ◽  
Novosibirsk Region ◽  
Stage 1 ◽  
The Unemployed

Aim. To determine the level of SARS-CoV-2 seroprevalence among the Novosibirsk Region population against the background of the COVID-19 pandemic.Material and methods. The work was carried out in 2 phases: 1) a cross-sectional cohort study performed 28.06– 15.07.2020; 2) longitudinal cohort 3-stage seromonitoring: 1st stage 28.06–15.07.2020; 2nd 14.09–04.10.2020; 3rd 10–30.12.2020 The work was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of St-Petersburg Pasteur Institute, taking into account the recommendations of the WHO. IgG antibodies to the SARS-CoV-2 nucleocapsid protein were detected by ELISA using a kit of reagents produced by the SRCMSB (Obolensk) according to the manufacturer’s instructions. Statistical analysis was performed using Microsoft Excel 2010 and other programs.Results. The seroprevalence in the region’s population was 9.1% (95% CI 8.0–10.2): maximum in children 14–17 years old (17.6%, 95% CI 12.3–23.9) and persons over 75 years (14.8%, 95% CI 11.4–18.8), minimum among persons 30–39 years old (4.9%, 95% CI 3.0–8.0). Increased rate was noted among the unemployed (15.4%, 95% CI 9.9–17.1) and other individuals (13.0%, 95% CI 8.6–18.5). Seroprevalence was 33.3% (95% CI 16.3–59.0) in COVID-19 convalescents and 19.0% (95% CI 13.9-25.0) in contact persons. More than 94.7% (95% CI 91.2–97.2) of seropositive individuals were asymptomatic. During the serological monitoring, seroprevalence increased from 7.4% (95% CI 6.2–8.9) at 1st stage 1 to 12.4% (95% CI 10.6–14.3) at 2nd , and 31% (95% CI 28.8–33.3) at 3rd stage.Conclusion. SARS-CoV-2 herd immunity has not reached the threshold level, this does not exclude exacerbation of the epidemic process.

scholarly journals SARS-CoV-2 seroconversion in health care workers

2020 ◽  
Author(s):  
Adrian M Shields ◽  
Sian E Faustini ◽  
Marisol Perez-Toledo ◽  
Sian Jossi ◽  
Erin L Aldera ◽  
...  
Keyword(s):  
Health Care ◽  
Health Care Workers ◽  
Cross Sectional Study ◽  
Asymptomatic Infection ◽  
Antibody Responses ◽  
Enzyme Linked Immunosorbent Assay ◽  
Nasopharyngeal Swab ◽  
University Hospitals ◽  
Cross Sectional ◽  
Care Workers

Background The correlates of protection against SARS-CoV-2 and their longevity remain unclear. Studies in severely ill individuals have identified robust cellular and humoral immune responses against the virus. Asymptomatic infection with SARS-CoV-2 has also been described, but it is unknown whether this is sufficient to produce antibody responses. Methods We performed a cross-sectional study recruiting 554 health care workers from University Hospitals Birmingham NHS Foundation Trust who were at work and asymptomatic. Participants were tested for current infection with SARS-CoV-2 by nasopharyngeal swab for real-time polymerase chain reaction and for seroconversion by the measurement of anti-SARS-CoV-2 spike glycoprotein antibodies by enzyme linked immunosorbent assay. Results were interpreted in the context of previous, self-reported symptoms of illness consistent with COVID-19. Results The point prevalence of infection with SARS-CoV-2, determined by the detection of SARS-CoV-2 RNA on nasopharnygeal swab was 2.39% (n=13/544). Serum was available on 516 participants. The overall rate of seroconversion in the cohort was 24.4% (n=126/516). Individuals who had previously experienced a symptomatic illness consistent with COVID-19 had significantly greater seroconversion rates than those who had remained asymptomatic (37.5% vs 17.1%, χ2 =21.1034, p<0.0001). In the week preceding peak COVID-19-related mortality at UHBFT, seroconversion rates amongst those who were suffering from symptomatic illnesses peaked at 77.8%. Prior symptomatic illness generated quantitatively higher antibody responses than asymptomatic seroconversion. Seroconversion rates were highest amongst those working in housekeeping (34.5%), acute medicine (33.3%) and general internal medicine (30.3%) with lower rates observed in participants working in intensive care (14.8%) and emergency medicine (13.3%). Conclusions In a large cross-sectional seroprevalence study of health-care workers, we demonstrate that asymptomatic seroconversion occurs, however prior symptomatic illness is associated with quantitatively higher antibody responses. The identification that the potential for seroconversion in health-care workers can associate differentially with certain hospital departments may inform future infection control and occupational health practices.

scholarly journals Seroprevalence of anti-SARS-CoV-2 IgG at the epidemic peak in French Guiana

2020 ◽  
Author(s):  
Claude Flamand ◽  
Antoine Enfissi ◽  
Sarah Bailly ◽  
Christelle ALVES SARMENTO ◽  
Emmanuel Beillard ◽  
...  
Keyword(s):  
Population Structure ◽  
Latin America ◽  
French Guiana ◽  
Herd Immunity ◽  
Health Centers ◽  
Spike Protein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Young Population ◽  
Cross Sectional Survey ◽  
Cross Sectional

Background SARS-CoV-2 seroprevalence studies are crucial for clarifying dynamics in affected countries and determining the route that has already been achieved towards herd immunity. While Latin America has been heavily affected by the pandemic, only a few seroprevalence studies have been conducted there. Methods A cross-sectional survey was performed between 15 July 2020 and 23 July 2020 in 4 medical biology laboratories and 5 health centers of French Guiana, representing a period shortly after the epidemic peak. Samples were screened for the presence of anti-SARS-CoV-2 IgG directed against domain S1 of the SARS-CoV-2 spike protein using the anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA) from Euroimmun. Results The overall seroprevalence was 15.4% [9.3%-24.4%] among 480 participants, ranging from 4.0% to 25.5% across the different municipalities. The seroprevalence did not differ according to gender (p=0.19) or age (p=0.51). Among SARS-CoV-2 positive individuals, we found that 24.6% [11.5%-45.2%] reported symptoms consistent with COVID-19. Conclusions Our findings revealed high levels of infection across the territory but a low number of resulting deaths, which can be explained by the young population structure.

scholarly journals Large-scale cross-sectional seroepidemiologic study of COVID-19 in Japan: Acquisition of herd immunity and the vaccines' efficacy

2022 ◽  
Author(s):  
Zhenxiao Ren ◽  
Mitsuhiro Nishimura ◽  
Lidya Handayani Tjan ◽  
Koichi Furukawa ◽  
Yukiya Kurahashi ◽  
...  
Keyword(s):  
Large Scale ◽  
Herd Immunity ◽  
Vaccination Rate ◽  
Enzyme Linked Immunosorbent Assay ◽  
Cross Sectional ◽  
Neutralizing Activity ◽  
Polymerase Chain ◽  
Hyogo Prefecture ◽  
Seroepidemiologic Study ◽  
Roll Out

Background: The COVID-19 pandemic situation has been changing drastically worldwide due to the continuous appearance of SARS-CoV-2 variants and the roll-out of mass vaccination. Periodic cross-sectional studies during the surge of COVID-19 cases is essential to elucidate the pandemic situation. Methods: Sera of 1,000 individuals who underwent a health check-up in Hyogo Prefecture Health Promotion Association clinics in Japan were collected in August and December 2021. Antibodies against SARS-CoV-2 N and S antigens were detected in the sera by an electrochemiluminescence immunoassay (ECLIA) and an enzyme-linked immunosorbent assay (ELISA), respectively. The sera's neutralization activities for the conventional SARS-CoV-2 (D614G), Delta, and Omicron variants were measured. Results: The seropositive rates for the antibody against N antigen were 2.1% and 3.9% in August and December 2021 respectively, demonstrating a Delta variant endemic during that time; the actual infection rate was approximately twofold higher than the rate estimated based on the polymerase chain reaction (PCR)-based diagnosis. The anti-S seropositive rate was 38.7% in August and it reached 90.8% in December, in concordance with the vaccination rate in Japan. In the December cohort, 78.7% of the sera showed neutralizing activity against the Delta variant, whereas that against the Omicron was much lower at 36.6%. Conclusions: These analyses revealed that herd immunity against SARS-CoV-2 including the Delta variant was established in December 2021, leading to convergence of the variants. The low neutralizing activity against the Omicron variant suggests the need for the further promotion of the prompt three-dose vaccination to overcome this variant's imminent 6th wave in Japan.

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