The UK government ’s chief scientific adviser, Patrick Vallance, recently stated that many organizations are conducting blood tests on COVID-19. He said “This will tell us who has been infected with this virus and now has antibodies, thus will not be infected again"

But is Vallance right? Once we have antibodies, are we protected?

Strictly speaking, not everyone who has not been infected with COVID-19 is immune to this disease. Our body does have the ability to protect itself. In addition, our immune system can learn and remove viruses during infection. This is basically the main method of treatment at present. The hospital supports COVID-19 patients while their own bodies are fighting the virus. Unfortunately, for too many people, the virus won this battle, and they left.

The immune system has several layers. The first and top layers consist of mechanical barriers, such as hair in the nose and mucus on the airways, which prevent pathogens (such as SARS-CoV-2) from entering the lung cells. Further down, these lung cells are filled with intrinsic defenses to prevent infection. But most viruses have evolved to bypass these defense systems and quickly defeat these defenses. This attack triggered the next wave of "innate" immunity. This includes a fast, broad-spectrum defense system, including direct antiviral killing mechanisms or promoting inflammation, thereby kicking the virus out of the body.

For most people, this natural response slows and controls the infection, making the last immune layer, adaptive immune system, work. Adaptive immunity consists of antibodies produced by B cells and antiviral killer cells, T cells. Both B and T cells can learn how to respond to specific threats during infection. This reaction usually takes a while to work, but it can remain for many years, forming a memory of past infections, such as MMR injections to prevent measles, mumps and rubella.
It is clear from the research conducted on SARS-CoV-2 that those infected with the SARS-CoV-2 virus will develop the above-mentioned multilayer immune response. In most cases, in the laboratory, antibodies produced during SARS-CoV-2 infection will bind, recognize, and prevent infection. However, there is not much information about the activity of T cells.

As more and more people infected this virus and survived by producing antibodies and T cells to fight against SARS-CoV-2, we may eventually reach a threshold of "herd immunity". This does not mean that everyone has immunity, but because most people have immunity, those susceptible people who do not have immunity are less likely to contract the disease.

The problem of achieving herd immunity through natural infection is that a large number of vulnerable people, such as those with weakened immune systems, pregnant women or the elderly, are likely to get sick and die. This is why obtaining high levels of vaccine-mediated immunity is essential to protect them. Ideally, we need a safe and effective vaccine to help us get immunized.
That is to say, as the pandemic develops, herd immunity may start to play a role later and help control infection in the short term. But this should not be the only target controlled by SARS-CoV-2. On the contrary, as outlined by the World Health Organization, active detection and isolation measures are the best way to slow the spread of this pandemic.

Since some detection methods have been developed so far, identifying people with SARS-CoV-2 antibodies (infected and recovered) will undoubtedly help determine the spread of a pandemic. But there are still many problems unsolved, for example, we don't know how long the immunity will last, and we don’t even know how many antibodies are needed to be classified as protected. A safe and effective vaccine will greatly eliminate this doubt, and should continue to maintain the key goal of combating COVID-19.

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Creative Diagnostics