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- With some viruses, once you have been infected and developed antibodies, you will be immune to that virus for life.
- Past infection with the SARS-CoV-2 virus, which causes Covid-19, does not guarantee, as far as is known at this stage, protection against future infections.
- Caroline Southey, editor of The Conversation Africa, asked Sehaam Khan and Saurabh Sinha to explain
What are antibodies and what is their function?
When a virus infects a host, it invades the host’s cells and replicates (makes copies of itself). One way our immune system protects us is to remove the virus from the body before it has a chance to infect a cell. The immune system has cells called B lymphocytes that make proteins called antibodies.
Antibodies recognize invading pathogens such as viruses and bind to them. The antibodies then neutralize or destroy the virus so that it cannot infect the host cell.
B lymphocytes also form memory cells that “remember” the pathogen. This allows the host to produce antibodies more quickly if there is an infection with that virus in the future.
For some viruses, like measles, for example, once a person has been infected, they are considered to have lifelong immunity. Other viruses mutate, so people can be affected more than once. The seasonal flu virus is one example.
What are the known and the unknown?
There are new things to learn about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the Covid-19 pandemic. It is not known how long a person is protected by antibodies after SARS-CoV-2 infection. The level of protection is also unknown. Measures to diagnose, mitigate, treat, and prevent infections continue to evolve. Policies are also evolving.
Globally, there have been some reports of patients testing positive, then negative, and then positive again for Covid-19. While this is still a rare event today, when a patient has symptoms and / or tests positive a second time, it could (in theory) be the same virus that infected the person the first time. In other words, the virus entered the body, caused illness, became inactive in the person, and then reactivated to cause illness again.
It could be that the body’s antibody protection has a limited life. Not much is known about the possibility of reinfection by the other two known coronaviruses, severe acute respiratory syndrome and Middle East respiratory syndrome. However, reinfections with the H1N1 virus have previously been reported.
One study addressed the possibility of reactivation of the SARS-CoV-2 virus in a single patient. Their findings suggest that this was not a case of reactivation. Instead, it suggests that the patient was separately infected by two genetic variants of the SARS-CoV-2 virus. It can be assumed that antibodies raised against variant one (if viable antibodies were still within the body) did not provide protection against variant two.
The patient in this study, similar to a study in Ecuador, had more severe symptoms during the second infection. In another study in the Netherlands, the second infection was fatal. The symptoms of most of the other patients during the second infection were comparable to those of the first round of infection. Some had no symptoms.
So if you have ever tested positive, there is a chance that you will contract the virus again. And you could possibly infect other people.
You still need to take the necessary precautions. Cover your nose and mouth with a mask, avoid touching your face, avoid large gatherings, maintain physical detachment, disinfect, and keep doors and windows open if possible. If you have flu-like symptoms or are exposed to an infected person, isolate yourself and be alert.
Why is the question of reinfection important in the search for a vaccine?
A vaccine is a biological agent that mimics an infection. It stimulates a person’s immune system (to produce lymphocytes and antibodies), while it almost never causes disease and protects the person from that disease.
Sometimes triggering a copycat infection produces minor symptoms, such as fever. This can be expected as the body develops immunity. After a few weeks, the body has a supply of lymphocytes that will remember how to fight that disease in the future. When enough people have been immunized, the virus will not have enough eligible hosts and should naturally go extinct.
For example, infectious diseases like measles, mumps, and polio were once common, but are now rare in most areas, because vaccines helped establish herd immunity.
When developing a vaccine, it should ideally make people immune to any variant of the virus. Many research groups have looked at the genetic diversity of the virus and whether mutations affect how the vaccine works.
One study has found that mutations in SARS-CoV-2 since the beginning of the pandemic are rare. This suggests that the potential vaccine candidates will cover all circulating variants.
The authors stated: “We can therefore be cautiously optimistic that viral diversity should not be an obstacle to the development of a broadly protective SARS-CoV-2 vaccine, and that vaccines in current development should elicit responses. reactive against SARS-CoV-2 variants. “
However, if the study of a patient who appeared to be infected twice by different genetic variants is accurate, it suggests that the antibodies raised against variant one did not provide sufficient protection against variant two. This has implications for vaccine development. The vaccine may only work for one variant or for a limited time.
While awareness of the virus increases daily, there are still many unanswered questions. Scientists from different areas of expertise must work together to learn about this virus in hopes of controlling it, if not eradicating it.
Sehaam khan, Professor (Microbiology and Molecular Virology) and Executive Dean: Faculty of Health Sciences, University of Johannesburg, University of Johannesburg and Saurabh sinha, Deputy Vice Chancellor: Research and Internationalization, University of Johannesburg
This article is republished from The conversation under a Creative Commons license. Read the Original article.
