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Swedish research reveals how long immunity lasts after coronavirus is mild

As a result of the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) outbreak and the ongoing coronavirus disease 2019 (COVID-19) related disease, global public health at risk has never been worse. than this

As a result of SARS-CoV-2 infection, antibodies are produced against several viral antigens. This includes spike and nucleocapsid proteins. There is evidence that antibodies to Spike-S1 proteins and in particular Receptor capture domain can neutralize the virus Research shows that people with severe infections are protected from the virus for months. But little is known about how long immunity lasts after a mild infection.

Research led by Asa Bjorndal of the Swedish Public Health Office examined the antibody responses of people after mild symptoms. The results showed that the antibodies Immunoglobulin G (IgG) targeting the spike protein remained stable after 8 months, but antibodies that target the nucleocapsid protein of SARS-CoV-2 declined over time.

The research team wrote:

“This unique serum sample panel presented will be useful for the diagnostic performance and quality assessment of current and new serum assays.”


The study, “Constant IgG-antibody Levels in Slightly SARS-CoV-2 Infected Patients” is available in a pre-printed form on www.sARS-CoV-2. medRxiv* server

Study: Stable IgG-antibody levels in slightly infected patients with SARS-CoV-2. Image credit: Corona Borealis Studio/Shutterstock.

how do they do it

Online advertisements promoting education help recruit participants from three Swedish counties. Potential participants completed an online questionnaire as a pre-screening measure of whether they were likely to donate serum samples containing positive or negative antibodies. and other demographic data? None of the participants received vaccine-activated antibodies. Because there is no vaccination campaign in Sweden yet.

patient characteristics

A total of 469 participants donated serum from October 30 to December 8, 2020 and were eligible for the study. Someone infected with COVID-19 Previously, of about 145 cases, preliminary randomization and follow-up revealed no cases of re-infection.

From a follow-up appointment scheduled for April 12, 2021, 28 of the 324 people who reported no previous infections were positive for SARS-CoV-2.

Approximately 85% of patients who test positive for SARS-CoV-2 report mild infections. with the most common flu-like symptoms People who have never been infected with COVID-19 report lung problems, and 17% believe they have contracted COVID-19 in 2020.

Positive serum and antibody tests

Approximately 95% of people who have recovered from COVID-19 Evidence of IgG antibodies specific to the nucleocapsid SARS-CoV-2 and spike protein was found. Four samples sampled for IgG antibodies showed evidence of other antibodies. that target nucleocapsids or spike proteins

Age and gender had no effect on immune or antibody levels.

Four percent who reported themselves never being infected turned out to be positive for antibodies targeting SARS-CoV-2. Of the 55 patients who reported uninfected but suspected of being infected with COVID-19, 10 were. infected

Correlation of patient-case antibody levels and time between disease notification and serum randomization (n = 141, negative 4 outliers).

Correlation of patient-case antibody levels and time between disease notification and serum randomization (n = 141, negative 4 outliers).

Those who reported moderate to severe disease had higher levels of antibodies to the spike protein and nucleocapsid. compared to those who reported mild symptoms.

The antibody test showed no difference in the levels of IgG to the spike protein over time. However, antibody levels to the nucleocapsid protein declined in patients diagnosed in the spring. compared to when it was tested again in the fall.

The results suggest that some antibodies obtained after recovering from a mild infection may decrease over time. It is difficult to find samples of a truly negative serum. which is a limitation in the study

While one of the strengths of the study was the broad sample from the general population found to have recovered from mild COVID-19, there was a possibility of bias in online recruitment sampling. Because the participants were not randomly selected. They suggest that the study results tend to underestimate the number of undiagnosed COVID-19 cases.


medRxiv Published preliminary scientific reports that have not been reviewed, so they should not be considered conclusive. Health-Related Clinical/Behavioral Practice Guidelines or is considered acceptable information

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