T-cell immunity found in SARS-CoV-2 infected individuals and close contacts who never experienced detectable infection

The following study was published by Nature Communications on March 19, 2021. The study’s main goal was to understand T-cell immunity among recovered COVID-19 patients and their close contacts.

This study found some very interesting results. Here are a few of them:

1. Most recovered COVID-19 patients have developed an effective memory T-cell pool against SARS-CoV-2.
2. Close contacts of SARS-CoV-2 patients also developed T-cell immunity even when all of those in the cohort tested negative for both the nucleic acid test (NAT, or more commonly known as RT-PCR) and antibody screening (also known as antibody test). This same observation was recorded during the MERS epidemic.
3. T-cell immunity in this instance was due less to pre-existing cross-reactive T cells from previous infection of common cold coronavirus. Majority of T-cell immunity that developed were SARS-CoV-2-specific. Upon closer inspection, the researchers also found that cross-reactive immunity has has some potential as a protective immune response, but not as strong as SARS-CoV-2-specific T immunity.
4. Memory T-cell immunity is detectable in both symptomatic and asymptomatic patients with confirmed COVID-19 infection.
5. There were no significant difference in the sizes of the SARS-CoV-2-specific memory T-cell pools between symptomatic and asymptomatic patients.
6. CD4+ T cell response was higher among asymptomatic patients while CD8+ T cell response was higher among symptomatic patients.
7. SARS-CoV-2-specific memory T-cells were stably maintained between 48-86 days after recovery.

The study adds that in rare instances, individuals who suffer severe and long-lasting symptoms of COVID exhibit low levels of SARS-CoV-2-specific T-cell immunity or antibody immunity.

Editor’s Note: This article is a bit technical and will require a working knowledge of terms in immunology. To help you process this article, we summarize some of the terms here:

CD4+ are helper T cells. They do not neutralize infections but rather trigger the body’s response to infections. They send out a “signal” to trigger the production of antibodies. Meanwhile CD8+ are killer T cells. Unlike other immune responses which releases antibodies into the bloodstream to neutralize pathogens, killer T-cells will go after human cells which have already been infected by the pathogen.

Based on this article, we can see clearly that natural infection of the virus will bring about short term and long-term immunity, both in asymptomatic and symptomatic patients. We also see that close contacts of COVID patients may have encountered smaller snippets of the virus, but that was enough for them to create T-cell immunity. This article adds to a growing body of resources showing us that the human immune system has the capacity to overcome SARS-CoV-2. It also helps us understand that it is possible to live normally with COVID – infection does not mean the end of the world. Like the flu, COVID can be an endemic disease that the body will be able to neutralize very easily.

What does it mean for us? For one, it means that a healthy immune system is the best defense against COVID. Second, any government intervention that prevents the healthy from encountering SARS-CoV-2 naturally prevents the development of long-term immunity from the virus and must be stopped. COVID’s low death rate among the young and healthy means that it is imperative to reopen societies and allow those who are not at risk to intermingle and develop SARS-CoV-2-specific T-cell immunity. This is how natural herd immunity will develop.

Experimental vaccines tout their effectiveness in the long term by measuring T-cell immunity among vaccine recipients. Unlike vaccines, however, natural infection does not require the injection of chemicals and synthetic materials in human bodies. If you are healthy, and you know that recovered COVID patients and close contacts get a healthy pool of SARS-CoV-2-specific T cells, which approach sounds more dangerous? [If you are concerned about the elderly and those with co-morbidities, countries can always implement focused protection to lessen their risk of death. The proposal for natural herd immunity does not mean we are proposing to leave the sick and elderly to die. See The Great Barrington Declaration: Life must return to normal for the healthy, the vulnerable must be protected].

New studies are also showing us that the immune system can mutate to handle variants. With this, we stress, herd immunity through natural infection is even more important, especially with the fast mutations happening with SARS-CoV-2, see Our immune system evolves to fight coronavirus variants.