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The antibody level of world population naturally infected by SARS-CoV-2

The antibody level of world population naturally infected by SARS-CoV-2. A study on the global antibody levels of people naturally infected with SARS-CoV-2 found that: herd immunity is hopeless.

Editor’s note:

The novel coronavirus pneumonia (COVID-19) has spread to more than 220 countries and regions around the world, causing a global pandemic. The sero-antibody positive rate study uses the antibody level to measure the degree of infection of the population under study. The presence of antibodies indicates that a person has been infected with SARS-CoV-2 or vaccinated against COVID-19. In the early stages of a pandemic, serological testing for specific antibodies against SARS-CoV-2 can better estimate the true number of infections, help retrospectively determine the scale or degree of infection in the study population, and provide information on how many A more complete picture of the population infected with SARS-CoV-2, and cases that have not been confirmed by routine or active testing.

This article reviews the global serum antibody levels of the general population naturally infected with SARS-CoV-2 and medical workers, children, pregnant women and other special populations. It is found that the positive rate of seroantibodies in people who are naturally infected with SARS-CoV-2 is reported globally. Different countries or regions are different, the positive rate ranges from less than 0.1% to more than 20%, and its level is related to different serological testing methods and the epidemic stage of the test. The seropositive rate of medical workers is not significantly higher than that of the general population; the seropositive rate of children is lower than that of other age groups; the seropositive rate of pregnant women is similar to that of the general population; the sera of asymptomatic infections and previously confirmed cases The positive rate of antibodies varies significantly in different studies, but related studies are limited. Therefore, it is necessary to continue to monitor the positive level of serum antibodies to assess the burden of disease caused by COVID-19.

The positive rate of SARS-CoV-2 seroantibodies in the general population

1. Europe

Switzerland

From 2020-04-06 to 2020-05-09, the study recruited 2,766 participants from 1,339 families with a population distribution similar to that of the Canton of Geneva, and used commercially available enzyme-linked immunosorbent reagents for each participant for 12 consecutive weeks. Serum anti-SARS-CoV-2-IgG antibody detection. The positive rates of seroantibodies in each week of the first 5 weeks were 4.8% [95% CI (2.4%, 8.0%)], 8.5% [95% CI (5.9%, 11.4%)], 10.9% [95% CI (7.9 %, 14.4%)], 6.6% [95% CI (4.3%, 9.4%)] and 10.8% [95% CI (8.2%, 13.9%)]. After using Bayesian logistic regression and considering the seroconversion time, it is estimated that 11.6 infections occurred for every confirmed case reported in the community.

Netherlands

A study conducted a high-efficiency immunoassay on 7361 routine plasma samples from blood donors for total antibodies to SARS-CoV-2 from April 1-15, 2020. The test results indicate serum antibodies in the Netherlands one month after the outbreak. The positive rate was 2.7%, and the most severely affected areas were as high as 9.5%. Another nationwide study from 2020-03-31 to 2020-05-11 used multiple immunization methods to quantitatively determine anti-SARS-CoV-2-IgG antibodies in 3207 participants. The positive rate of serum antibodies was 2.8% (95% CI) (2.1%, 3.7%)], the highest (4.9%) among 18 to 39-year-olds, and the lowest among 2-17-year-olds (1.7%).

Italy

From 2020-05-11 to 2020-07-05, the study performed chemiluminescence immunoassay (CLIA) serological screening on 2753 people who were treated in the main Milan hospitals, and the results showed accumulated serum SARS-CoV-2-IgG The positive rate was 5.1% [95% CI (4.3%, 6.0%)], and reached 8.4% [95% CI (6.1%, 11.4%)] 60 to 63 days after the peak of diagnosis (March 2020) At the peak, only one-third of the 18 patients with positive RT-PCR and symptomatic patients were positive for SARS-CoV-2-IgG, and it increased to two-thirds in patients who recovered clinically.

Scotland

The study analyzed 3,500 blood donor samples obtained from March to May 2020. The positive rate of seroantibodies detected by the virus neutralization assay (VNT) was 3.2%. A separate analysis of 490 samples collected from the central area of the outbreak showed that The positive rate of serum antibody was 8.57%.

Spain

The nationwide study recruited 61,075 participants from 2020-04-27 to 2020-05-11 and underwent serological testing by real-time antibody detection and chemiluminescence particle immunoassay, and the positive rate of seroantibodies in the immediate detection was 5.0% (95) %CI (4.7%, 5.4%)], the immunoassay result was 4.6% [95%CI (4.3%, 5.0%)], the positive rate of seroantibodies in children under 10 years of age was lower (immediate detection <3.1%) .

France

The study used the virus neutralization assay (VNT) to detect 998 samples collected from blood donors. The positive rate of seroantibodies was 2.7%, but the positive rate of seroantibodies of type O blood donors was significantly lower (for type O blood donors) 1.32%, 3.86% for donors of other blood types, P=0.014).

2. Asia

India

A cross-sectional study from 2020-07-01 to 2020-07-15 used chemiluminescent microparticle immunoassay to detect SARS-CoV-2 specific IgG antibodies in 2906 people over 18 years old, standardized for age and gender The positive rate of serum antibody afterwards was 3.6% [95% CI (2.9%, 4.3%)].

Another national study conducted from 2020-05-11 to 2020-06-04 randomly recruited 28,000 people from 70 regions in 21 states in India for ELISA serological testing, adjusted population-weighted serum antibodies The positive rate was 0.73% [95% CI (0.34%, 1.13%)].

Iran

A cross-sectional study used the ELISA test method to detect and analyze the SARS-CoV-2 seroantibody positive rate in the general population (3530 people) and high-risk occupational population (5372 people) in 18 cities. The overall population (8902 people) In ), the adjusted seroantibody positive rate was 17.1% [95% CI (14.6%, 19.5%)], 20.0% [95% CI (18.5%, 21.7%)] among high-risk groups, varying between occupations Not big.

Korea

A cross-sectional serum monitoring study used electrochemiluminescence immunoassay (ECLIA) for serological determination in 1500 hospital outpatients in southwestern Seoul. The positive rate of SARS-CoV-2 antibody was 0.07% [95% CI (0, 0.44) %)].

China

A study conducted in Taiwan used ELISA to detect blood samples from a total of 14,765 patients. After weighting Taiwan’s demographic data, the sero-antibody positive rate was estimated to be 0.05% [95% CI (0.02%, 0.10%)]. In a Hong Kong serological study of 452 people who returned from Hubei Province in March 2020, the sero-antibody positive rate was 4%, most of which (88%) were confirmed by the micro-neutralization test. The National Seroepidemiological Survey of New coronavirus Pneumonia organized by the Chinese Center for Disease Control and Prevention used a cross-sectional survey method to sample more than 34,000 people in the community. The survey time was one month after the first wave of COVID-19 was contained, and it was discovered that Wuhan The positive rate of seroantibodies in the community population in the region was 4.43%, and the positive rate of seroantibodies in the cities and prefectures outside Wuhan, Hubei was 0.44%. Among more than 12,000 people in six provinces outside Hubei, only 2 cases of seroantibodies were detected, and the positive rate was extremely low. The test results have been reviewed by the cell micro-neutralization test. The positive rate of antibodies in people who have been exposed to confirmed cases of COVID-19 is significantly higher than that of other people, and the positive rate of antibodies in the middle-aged and elderly population is higher than that of other age groups.

3. America

United States

In a cross-sectional study conducted in July 2020, 28,503 dialysis patients were subjected to plasma total antibody chemiluminescence analysis using a spike protein receptor binding agent. The positive rate of SARS-CoV-2 serum antibody was 8.0% (95%) CI (7.7%, 8.4%)]. After adjusting for the standardization of the American adult population, the positive rate of seroantibodies was 9.3% [95% CI (8.8%, 9.9%)]. Another nationwide reproducible cross-sectional study conducted from July to September 2020 used chemiluminescence immunoassay for SARS-CoV-2 antibody detection on 177919 clinical blood samples. In 4 collection periods, serum antibodies in each district were positive The rate is 1%~23%.

Brazil

Two repetitive cross-sectional seroantibodies surveys were conducted in 133 cities in all states. Both surveys were conducted using lateral flow immunochromatography (LFIA). The results showed that the total seroantibodies in the two surveys were positive The rate increased from 1.9% [95% CI (1.7%, 2.1%)] to 3.1% [95% CI (2.8%, 3.4%)].

4. Global

ROSTAMI et al. collected research data on the seroantibody positive rate of 47 populations that met the inclusion criteria on a global scale for systematic review and meta-analysis. There were a total of 399,265 people in 107 data sets from 23 countries. The study found that SARS-CoV in the general population -2 The positive rate of seroantibodies is between 0.37% and 22.1%, and the estimated positive rate of seroantibodies is 3.38% [95% CI (3.05%, 3.72%)]. The positive rates of seroantibodies in all continents are 5.27% in Northern Europe, 4.41% in Southern Europe, 4.41% in North America, 3.17% in Western Europe, 2.02% in East Asia, and 1.45% in South America. The countries with the highest sero-positive rate are Iran (22.1%), Sweden (15.02%), Chile (10.7%), Switzerland (7.9%), South Korea (7.5%), Italy (7.27%), Spain ( 5.0%) and the United States (4.4%).

The difference in the positive rate of serum antibodies is related to the serological testing methods used. Subgroup analysis showed that the positive rates of seroantibodies measured using LFIA, ELISA, CLIA, virus neutralization assay, and microsphere immunoassay were 3.95%, 3.53%, 2.73%, 1.32%, and 12.50%, respectively; using commercial laboratory serum The total antibody positive rate was 3.33% [95% CI (2.95%, 3.71%)], and the rate of using internal tests was 3.63% [95% CI (2.79%, 4.48%)].

The subgroup analysis explored the time from the beginning of the pandemic to the sampling and testing of various studies, and found that the positive rate of SARS-CoV-2 seroantibodies changed with the prolonged epidemic time. The results showed that the positive rate of seroantibodies in a country was lowest at the beginning of the COVID-19 epidemic, higher at 70 days, and highest at 4 months after the beginning of the epidemic (P=0.001). Random-effect Meta analysis showed that the positive rate of serum antibodies showed an increasing trend over time (C=0.002, P=0.02).

Positive rate of SARS-CoV-2 seroantibodies in special population

1. Medical staff

Greece

The study recruited 321 medical staff from two tertiary hospitals in Athens and used the ELISA method for antibody testing. The results showed that the sero-antibody positive rate was 2.18%. The nucleic acid PCR test of the sero-positive medical staff was negative.

France

The study included 8758 medical staff to participate in ELISA serological antibody testing, and the overall sero-antibody positive rate was 3.2% [95% CI (2.8%, 3.5%)]. The seropositive rate was highest for physical therapists (9.2%), followed by public health service staff (7.3%), school health training department staff (6.9%) and infectious disease department staff (6.7%). In another study conducted from 2020-05-02 to 2020-06-26, 3,569 medical staff in various departments of the hospital used Abbott’s SARS-CoV-2-IgG test, and the positive rate of serum IgG was 11.9% ( 423/3569).

India

The study conducted electrochemiluminescence automatic immunoassay on blood samples of 801 medical staff (400 from COVID-19 designated hospitals and 401 from non-COVID-19 designated hospitals), and the overall sero-antibody positive rate was 11.1% (95%) CI (9.1%, 13.5%)], the seropositive rate of auxiliary workers (18.5%) was significantly higher than that of doctors (7%) and nurses (6.8%), and the seropositive rate of medical staff in non-COVID-19 designated hospitals The rate (13.5%) is significantly higher than that of medical staff in COVID-19 designated hospitals (8.7%).

2. Children and pregnant women

United Kingdom

The multi-center observational cohort study conducted from 2020-04-16 to 2020-07-03 analyzed the seropositive rate of 992 children aged 2-15 years in the family of medical staff. A total of 68 (6.9%) children had SARS- A positive CoV-2 antibody test indicates that he had a previous SARS-CoV-2 infection, and half of them were asymptomatic before the test. Independent variables that are significantly related to SARS-CoV-2 serum antibody positive are: infection in the family, fatigue, gastrointestinal symptoms, and changes in smell or taste.

Czech Republic

In July and August 2020, the study screened 200 children (0-18 years old) who were treated in the pediatrics department of a hospital for SARS-CoV-2 antibodies for diseases unrelated to COVID-19. No seropositive persons were found.

France

The study provided 272 pregnant women with SARS-CoV-2 serological testing. The positive rate of seroantibodies was 8%, the positive rate of RT-PCR was 0.5%, and 47.4% of SARS-CoV-2-IgG positive pregnant women never had any symptom.

Spain

The study tested 874 pregnant women from 2020-04-14 to 2020-05-05 for anti-SARS-CoV-2 IgG, IgM and IgA antibody, the total serum antibody positive rate is 14%, 15% of pregnant women in the first 3 months of pregnancy, 14% of pregnant women in the second trimester, and more than half of the antibody-positive pregnant women have no symptoms.

3. Asymptomatic infections and previously confirmed cases

Germany

An exploratory single-center study conducted in northern Germany showed that 118 patients diagnosed with SARS-CoV-2 had IgA and IgG antibodies that appeared 3 weeks or later after infection, and 82% of all patients developed SARS-CoV-2. With persistent antibody IgG, 78% produced IgA, and most seronegative patients had no or only moderate symptoms.

Italy

A follow-up study of 31 cases of asymptomatic infections showed that at least one of the nucleic acid and serum antibody tests was positive. At the first test, 21 cases were nucleic acid positive and 17 cases were seroantibodies; the second test was performed 8 weeks later. About 80% of the nucleic acid-positive asymptomatic infections did not have serum antibodies against SARS-CoV-2; in the first sample of nucleic acid-positive patients, 8 cases (38%) were antibody-positive, and only 3 cases (14.3%) were in 8 cases. The serum IgG level remained at a measurable level after one week.

Expert comments on this article:

(1) So far, most serological studies have mainly focused on people who are naturally infected with SARS-CoV-2. The study of serum antibody levels in people who are naturally infected with SARS-CoV-2 is useful for retrospective evaluation of the epidemic situation of the study population The scale and degree of infection are important.

At present, the positive rate of seroantibodies in people who are naturally infected with SARS-CoV-2 ranges from less than 0.1% to more than 20%. The positive rate of seroantibodies has different meanings at different stages of the epidemic and can be used to assess the vulnerability of local populations.

Sensibility, degree of infection, and hygiene prevention and control effect. In the early stage of the pandemic, the low seropositive rate of SARS-CoV-2 indicates that the population is highly susceptible; in the middle and late stages of the pandemic, the seropositive rate of most countries and regions continues to increase, and the low seropositive rate reflects good social isolation And epidemic prevention and control effects (such as China).

With the success of vaccine research and development and the advancement of vaccination work, in the future, serum antibody levels and immunity persistence studies can be carried out on the vaccinated population to evaluate the population’s immunity level and vaccine immunity, in order to better prevent and control the epidemic.

(2) The seropositive research of people naturally infected with SARS-CoV-2 involved in this review covers a wide range, from the early stage to the middle of the epidemic, and because different countries are in different epidemic states, different detection methods, and quality control measures There may be differences in aspects such as, therefore, it may have a certain degree of impact on the true level of seroantibodies in the population, and limit the comparison of seroantibodies in different populations.