Scientists Uncover Evidence That a Level of Pre-Existing COVID-19 / SARS-CoV-2 Immunity Is Present in the General Population

SARS-CoV-2-Specific T Cell

A Singapore study has found that individuals who recovered from COVID-19 and SARS, as well as some uninfected individuals, possess virus-specific T cell immunity.

Singapore scientists uncover SARS-CoV-2-specific T cell immunity in recovered COVID-19 and SARS patients, and in uninfected individuals.

  • Singapore study shows that SARS-CoV-2-specific T cells are present in all recovered COVID-19 patients.
  • These T cells were also found in all subjects who recovered from SARS 17 years ago, and in over 50% of both SARS-CoV-1 and SARS-CoV-2 uninfected individuals tested, suggesting that a level of pre-existing SARS-CoV-2 immunity is present in the general population.
  • Infection and exposure to coronaviruses induces long-lasting memory T cells, which could help in the management of the current pandemic.

The T cells, along with antibodies, are an integral part of the human immune response against viral infections due to their ability to directly target and kill infected cells. A Singapore study has uncovered the presence of virus-specific T cell immunity in people who recovered from COVID-19 and SARS, as well as some healthy study subjects who had never been infected by either virus.

The study by scientists from Duke-NUS Medical School, in close collaboration with the National University of Singapore (NUS) Yong Loo Lin School of Medicine, Singapore General Hospital (SGH) and National Centre for Infectious Diseases (NCID) was published in Nature. The findings suggest infection and exposure to coronaviruses induces long-lasting memory T cells, which could help in the management of the current pandemic and in vaccine development against COVID-19.

The team tested subjects who recovered from COVID-19 and found the presence of SARS-CoV-2-specific T cells in all of them, which suggests that T cells play an important role in this infection. Importantly, the team showed that patients who recovered from SARS 17 years ago after the 2003 outbreak, still possess virus-specific memory T cells and displayed cross-immunity to SARS-CoV-2.

“Our team also tested uninfected healthy individuals and found SARS-CoV-2-specific T cells in more than 50 percent of them. This could be due to cross-reactive immunity obtained from exposure to other coronaviruses, such as those causing the common cold, or presently unknown animal coronaviruses. It is important to understand if this could explain why some individuals are able to better control the infection,” said Professor Antonio Bertoletti, from Duke-NUS’ Emerging Infectious Diseases (EID) program, who is the corresponding author of this study.

Associate Professor Tan Yee Joo from the Department of Microbiology and Immunology at NUS Yong Loo Lin School of Medicine and Joint Senior Principal Investigator, Institute of Molecular and Cell Biology, A*STAR added, “We have also initiated follow-up studies on the COVID-19 recovered patients, to determine if their immunity as shown in their T cells persists over an extended period of time. This is very important for vaccine development and to answer the question about reinfection.”

“While there have been many studies about SARS-CoV-2, there is still a lot we don’t understand about the virus yet. What we do know is that T cells play an important role in the immune response against viral infections and should be assessed for their role in combating SARS-CoV-2, which has affected many people worldwide. Hopefully, our discovery will bring us a step closer to creating an effective vaccine,” said Associate Professor Jenny Low, Senior Consultant, Department of Infectious Diseases, SGH, and Duke-NUS’ EID program.

“NCID was heartened by the tremendous support we received from many previous SARS patients for this study. Their contributions, 17 years after they were originally infected, helped us understand mechanisms for lasting immunity to SARS-like viruses, and their implications for developing better vaccines against COVID-19 and related viruses,” said Dr Mark Chen I-Cheng, Head of the NCID Research Office.

The team will be conducting a larger study of exposed, uninfected subjects to examine whether T cells can protect against COVID-19 infection or alter the course of infection. They will also be exploring the potential therapeutic use of SARS-CoV-2-specific T cells.

Reference: “SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls” by Nina Le Bert, Anthony T. Tan, Kamini Kunasegaran, Christine Y. L. Tham, Morteza Hafezi, Adeline Chia, Melissa Hui Yen Chng, Meiyin Lin, Nicole Tan, Martin Linster, Wan Ni Chia, Mark I-Cheng Chen, Lin-Fa Wang, Eng Eong Ooi, Shirin Kalimuddin, Paul Anantharajal Tambyah, Jenny Guek-Hong Low, Yee-Joo Tan and Antonio Bertoletti, 15 July 2020, Nature.
DOI: 10.1038/s41586-020-2550-z

15 Comments on "Scientists Uncover Evidence That a Level of Pre-Existing COVID-19 / SARS-CoV-2 Immunity Is Present in the General Population"

  1. Was it determined if the immunity was gained through taking the flu vaccine?

    • The memory T Cells researched in this study are an immune response to a coronavirus (of which there are 7 which infect humans, SARS-CoV-1, SARS-CoV-2, MERS and 4 cold viruses). These T cells will have no effect on an influenza virus and it is not possible for such corona effective T cells to have been formed by a influenza vaccine.

  2. Does this mean that with great increase in testing, that is why we we are so many positive test results.

    • No. The Covid tests look for either the SARS-CoV-2 virus itself or active antibodies specific to SARS-CoV-2. Antibodies last weeks to months after an infection has been defected.
      Memory cells are a type of immune cell that are specific to a given virus and hang around after someone has recovered from an infection. If those memory cells again encounter that virus, years to decades later, they can quickly create the needed antibodies again.
      Memory cells aren’t detected by the normal covid tests.

  3. to #1 it was believed that immunity was gained from exposure to other coronaviridae such as the ones that cause the common cold in the past, not the flu or flu vaccine as this is a different type of virus altogether.

    #2 Increases in testing will lead to more positive results in general but this doesn’t completely explain the numbers, there are simply more people getting sick with the novel cornoavirus. Be careful.

    -anonymous MD

  4. Suggests virus was designed to weaken western nations.

    • Makes no sense because that’s the market China and other eastern countries sell most to, so it weakens them as well. You need a new conspiracy theory.

  5. Dr Osita Godornes | July 26, 2020 at 5:58 pm | Reply

    Thank you it is very informative lessons and ideas and of great help to our patienfs, we the frontliners and the general population good day

  6. Anthony J Leonardi, PhD | July 26, 2020 at 7:46 pm | Reply

    People have rabies t cells as well. Libraries of t cells exist against cancers and viruses that humans have not been exposed to, inside their bodies. What do you think the vaccine is doing? It’s just stimulating those cells so they are poised to fight the virus. It’s why you get a rabies vaccine even after you’re infected- so you can train the t cells that already exist inside you to kill infected cells. This is not ‘prior immunity’.

  7. So, those exposed to merscov has already t-cells or memory cells?

  8. Even though the T cells are not formed due to the flu shot, why cant we advocate the flu shot for the entire population so that we can reduce the anxiety caused due to overlapping symptoms of cold, cough, fever, body pain, sore throat, etc? At least we can reduce the number of individuals thronging to the hospitals for non covid respiratory illnesses.

    • Mature member of society | August 21, 2020 at 11:28 pm | Reply

      In short, it’s not the right choice for the ENTIRE population. Side effects, religious beliefs, etc.

  9. Have children of the adults with immunity,inherited this immunity?

  10. Go out and open mouth kiss everything and everyone.

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