[serum IgM and IgG antibodies against new coronavirus] Lu Mingling: changes and application of serum IgM and IgG antibodies after new coronavirus infection or vaccination

Novel coronavirus pneumonia (novel coronavirus pneumonia), a novel coronavirus pneumonia, has been infected by COVID-19 in 2019

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The 10 cases of infectious diseases in Nanning have been infected by imported new cases and local clustering cases

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Sporadic cases of sporadic cases are common, and new and old infections coexist

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The novel coronavirus pneumonia epidemic prevention and control work has been brought to light by the rapid development and use of vaccines

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Since July 2020, new coronavirus vaccination has been carried out among key employees (medical and disease control, imported cold chain, public transport and other people with high risk of infection) in China

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So far, more than 30 million people have been vaccinated

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A large number of people in China have antibodies to new coronavirus

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Novel coronavirus pneumonia is a new type of pneumonia

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However, there is no clear plan for the management of antibody positive personnel after vaccination in China, so the epidemic prevention and control work is facing new challenges

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This article is mainly novel coronavirus pneumonia infection or vaccination after the change of antibody level and application to make a brief introduction, and after the recommendation of COVID-19 vaccination, it is unnecessary to go to the hospital to screen antibodies

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1、 The immunoglobulin is a kind of serum active component produced by human body under the stimulation of virus antigen substance, which can specifically combine with antigen to form antigen antibody complex and block the damage of virus to human body

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It includes IgM, IgG, IgA, IgD and IgE

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The content of IgE and IgD in serum is very low, and the half-life of IgA is short

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Therefore, the detection of IgM and IgG antibodies in serum is usually used to judge the previous infection of new coronavirus or evaluate the effect of vaccine

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IgM antibody is often detected 3-5 days after the onset, lasting more than 40 days

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It is a diagnostic indicator of acute infection

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IgG antibody is usually detected 5-10 days after the onset of symptoms, lasting for about 3-6 months

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It is a diagnostic indicator of late or previous infection

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It has been reported that the level of antibody in serum is related to the positive degree of patients’ symptoms

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The more serious the symptoms are, the higher the average levels of IgM and IgG in serum are (Fig

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1)

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Figure 1: comparison of antibody levels in patients with different symptoms

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2

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If the antibody test result is negative, it must not be infected with the virus? no The existence of window period of antibody expression, low detection sensitivity, improper sample storage or laboratory operation, weak antibody response of mild patients, low level of antibody degradation caused by sample inactivation, etc

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may lead to false negative detection

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3、 Is antibody test result positive infected virus certainly? no Different species of coronavirus N protein or S protein exist immune cross reaction; the examinee has high concentration of rheumatoid factor; laboratory or kit contamination; weak positive patients may have a part of false positive, it is recommended to review after 3-5 days; sample hemolysis, incomplete coagulation of blood samples, jaundice patients may lead to false positive

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Four

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The novel coronavirus pneumonia antibody detection value in the detection of antibodies can be used for the auxiliary diagnosis of COVID-19 infection or vaccine immune effect evaluation

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After obtaining the antibody test results, we should carefully consider the history of the patients, vaccination history and the history of basic diseases

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Nucleic acid detection is the gold standard to determine whether the new coronavirus is infected or not, but both have their own advantages and can not replace each other

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After infection, human viral load and antibody level showed different changes (see Figure 2 for details)

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The sensitivity of nucleic acid detection and antibody detection was different

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The detection rate of nucleic acid decreased in the middle and late stage of infection, and the detection rate of antibody was high

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The combination of the two can reduce the rate of missed diagnosis

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Therefore, after the detection of new coronavirus antibody in serum, we should review the virus nucleic acid at intervals according to the actual situation (Fig

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3)

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Fig

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2: novel coronavirus pneumonia in COVID-19 infection: Tutu 3: New Coronavirus nucleic acid and antibody test results five

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Do we need to detect antibodies specifically after the novel coronavirus pneumonia vaccine? unwanted! There is no need to carry out routine antibody detection for the people who have been vaccinated with the new coronavirus vaccine

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The reasons are as follows: (1) not all vaccinated people will produce antibodies

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After vaccination, the vast majority of people can produce antibodies

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From the current vaccine clinical research results, it can be seen that more than 97% of the vaccinated people can produce neutralizing antibodies, which is the standard in clinical trials And antibody test, that is to say, it is impossible to produce 100% antibody after vaccination

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(2) Different detection methods and reagents have different detection results

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At present, N protein and S protein are used as capture antigens in antibody reagents for detection of new coronavirus

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Different detection methods choose different types of antibodies to be detected, such as single detection (IgM or IgG), double detection (IgM + IgG) or total antibody detection (IgM + IgG + IGA), which are commonly used by medical institutions and third-party detection institutions The detection was double detection (IgM + IgG)

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Different detection reagents have different principles, captured antigens and detected antibodies, which lead to different sensitivity

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In other words, different detection methods will have higher false positive or false negative results, and the single test result is not necessarily reliable

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(3) Antibody test results can not be used as the basis for vaccine protection

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At present, the novel coronavirus antibody detection methods mainly include chemiluminescence method, colloidal gold method and fluorescence immunochromatography, which are qualitative detection

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Quantitative analysis can not be done for antibodies in vivo

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It can only give the judgment that the antibody is positive or negative, and can not quantitatively determine the antibody level

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That is to say, antibody detection is positive, and can only be used The results showed that the vaccine caused immune reaction in the body, but the antibody had protective effect

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References: [1] the best doctor in human beings is oneself — on immunoglobulin and human health

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China immunology Journal.2016; 32 (12): 1889-90.[2] China Hospital Association clinical microbiology laboratory Specialized Committee

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New Coronavirus laboratory testing expert consensus [J]

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Concord Medical Journal, 2021, 12 (1): 18-26

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doi:10.12290/xhyxzz.2020-0046 .[3] HuanMa,  WeihongZeng,etal. SerumIgA,IgM,andIgGresponsesinCOVID-19 [J]. Cellular&MolecularImmunology,2020, 17:773–775.。

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