Study: Less than 80% of people infected with SARS-CoV-2 have detectable antibodies

Mihai-Alexandru Cristea 23/11/2020 | 17:29

Since the first cases of COVID-19 were detected, consistent efforts are being made to develop a vaccine and identify a valid general treatment, but also to fully understand how the SARS-CoV-2 virus works and how the human body responds to it. While scientists are working hard on several fronts, the immunity developed by patients currently remains an important method to measure recovery and resistance to the virus. In August, REGINA MARIA Health Network launched a study to investigate the immune response of patients infected with the new coronavirus, by applying international information and contextualizing it locally.

 

The body’s “memory” is a key element of the infection with the SARS-CoV-2 virus, as is the case with patients’ immune responses in other diseases developed as a result of infection with various types of viruses. When we talk about immunity, we refer to the possibility of generating an immune response that protects us. This response may or may not be long long-lasting.

The first cases of COVID-19 reinfection brought us to the point where it is important to know how long we are protected from this virus and how it continues to evolve.

 

Objective of the study: How does the body behave after SARS-CoV-2 infection?

“Certain pathogens do not stimulate the production of antibodies and an episode of disease does not provide us with immunity against them. They trick the immune system not to detect them as foreign particles and eliminate them as our body is taught. An example of such a pathogen is the HIV virus, which disguises itself and manages to reach the inside of human cells. The new coronavirus invades the body though a mechanism that is not very well known and it must be further studied to see why some patients do not produce antibodies”, says Dr. Andreea Alexandru, Primary Laboratory Physician and Medical Director at the REGINA MARIA Clinical Laboratories Division.

There are several questions about how the body currently behaves after the infection with the new coronavirus, how it works and how long we are protected from a second infection. Therefore, REGINA MARIA Health Network conducted a study between August and September 2020 to find out more about the impact of the virus on a person known to have been cured of the infection, by monitoring the immune response of patients affected by the virus.

Study methodology:

  • Period: August – September 2020
  • Location: Bucharest, Cluj
  • Number of participants: 239 patients tested positive for coronavirus by July 31

 

79% of people infected with SARS-CoV-2 had detectable antibodies at the time of testing

Patients who were part of the study conducted by REGINA MARIA were tested for antibodies within an average length of time of 43-56 days from receiving a positive result of the RT-PCR test. They had mild, moderate, severe forms or were asymptomatic.

“The immune system will always fight against everything that is non-self (not of the body) in different ways, with different weapons. Some of these weapons are called antibodies. IgM antibodies are produced in the acute phase of a disease, on average in the first two weeks after the body meets the “enemy” – the CoVID-19 virus. IgG antibodies are produced after 2 weeks from the time of infection, during the recovery/convalescence period. The body needs these weeks to mobilize the resources and systems involved in the production of these antibodies (“an army of soldiers well trained to recognize a certain type of enemy and fight it”), adds Dr. Andreea Alexandru.

After testing 350,000 patients, the REACT-2 study conducted by the Imperial College Team in London, confirmed a 26% drop in antibody levels 3 months after infection.

The longevity of the antibody response is still far from being precise, but according to the European Center for Disease Prevention and Control (ECDC) antibodies against coronaviruses generally have short viability and protection (an average of 12 – 52 weeks after the onset of symptoms) and cases of reinfection may occur. The same source tells us that IgG antibody levels of SARS-CoV-2 may remain for seven weeks or, at least in 80% of cases, until day 49.

 

Severe cases of COVID-19 appear to be better protected from reinfection than mild ones

At first glance, we may be skeptical about this fact, but the severity of COVID-19 is directly proportional to the increase in the number of patients with antibodies. Data presented by the REGINA MARIA study show that patients who had an asymptomatic or mild form with minimal symptoms displayed antibodies to a lesser extent than patients who had moderate or severe forms.

King’s College London has been monitoring the antibody response in patients and healthcare workers since the beginning of the pandemic, in the first longitudinal study of the kind. This study showed that there were more patients with severe forms, suffering from fever or respiratory problems for several weeks, who developed antibodies than those with mild symptoms. The REGINA MARIA study also confirms this aspect, analyzed at local level: only 68% of asymptomatic patients displayed antibodies as compared to 89% of patients with severe forms.

 

Age is a risk factor for severe cases of COVID-19

Data from REGINA MARIA indicate an increased risk of developing a moderate/severe form of COVID-19 for patients over 59 years of age. World Health Organization warned that the virus causes a higher mortality rate in older adults as well as in those with comorbidities such as hypertension, cardiovascular diseases, diabetes, chronic respiratory diseases, and chronic kidney diseases.

 

Groups under 20 and over 50 years of age have a higher proportion of antibodies

The study conducted by REGINA MARIA also reveals an important aspect: if all young people under 20 tested in the study displayed antibodies after infection, the post-infection positivity curve decelerates in adults between 20 and 50 years of age, and then returns to high levels of positivity as the age begins to grow again. Why does this happen? Researchers are still studying the human mechanisms that generate this behavior, but information is still essential for the healthcare system in the management of patients.

 

Virus immunization: group or individual?

The governments of each country have adopted local measures they deemed necessary. Sweden’s special case raised many questions when it relied on group immunity at the onset of the pandemic, on the recommendation of leading epidemiologist Dr. Anders Tegnell. However, he recently said that this method proved to be “useless and immoral”, and the country implemented the first regional measures after seeing record levels of infection.

The US government’s leading epidemiologist, Dr. Anthony Fauci, says that in the United States, where the infection curve has grown exponentially with the pandemic, group immunity is unlikely to be achieved soon.

Collective immunity is a highly debated topic in the context of the coronavirus epidemic, yet it offers solutions: “I don’t think we will be able to eradicate it. We may not completely eliminate the virus, but if it is reduced to a low level and a large enough population is protected – either by a vaccine or by immunization after healing – there will be no more outbreaks.”

As long as research continues, the only way to protect against the virus remains prevention in social behavior. Meanwhile, the study of patients’ immunization after SARS-CoV-2 infection continues, contributing to the overall effort to find real scientific solutions and answers.

 

Sources:

  1. https://www.ecdc.europa.eu/en/covid-19/latest-evidence/immune-responses
  2. https://www.nejm.org/doi/pdf/10.1056/NEJMc2025179?articleTools=true
  3. https://www.thelancet.com/journals/lanrhe/article/PIIS2665-9913(20)30212-5/fulltext#%20
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7324116/
  5. https://www.who.int/docs/default-source/coronaviruse/risk-comms-updates/update-34-immunity-2nd.pdf?sfvrsn=8a488cb6_2
  6. https://www.genengnews.com/news/comparing-covid-19-immune-responses-uncovers-key-differences-between-adults-and-children/
  7. https://stm.sciencemag.org/content/12/564/eabd5487
  8. https://www.nature.com/articles/s41591-020-0962-9
  9. https://medicalxpress.com/news/2020-10-autoimmune-like-antibody-response-linked-severe.html
  10. https://www.cdc.gov/mmwr/volumes/69/wr/mm6915e3.htm?s_cid=mm6915e3_w
  11. https://www.e-agmr.org/journal/view.php?number=924
  12. https://www.researchgate.net/publication/340493238_Covid-19_and_Older_Adults_What_We_Know
  13. https://www.healthline.com/health-news/older-adults-are-more-at-risk-for-covid-19-so-why-dont-vaccine-trials-include-them
  14. https://www.nature.com/articles/s41564-020-00813-8
  15. https://www.news-medical.net/news/20200818/Antibody-and-cellular-immunity-in-severe-vs-mild-COVID-19.aspx
  16. https://www.the-scientist.com/news-opinion/immune-biomarkers-tied-to-severe-covid-19-study-67843
  17. https://www.sciencemag.org/news/2020/09/uncoordinated-immune-response-may-explain-why-covid-19-strikes-some-hard-particularly
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