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Do people who have been infected with previous coronavirus-type infections have some level of immunity COVID-19?

Question: Is there any research as to whether people who have been infected with previous coronavirus-type infections in the past have some level of immunity to this strain?

Answer: Short answer== YES! One of the big outstanding questions is why the severity of SARS-CoV-2 infection varies so dramatically from person to person. We talked about this issue a little back in our Q&A of 5/9 (#Kids), which also provides a very quick synthesis of how the immune system works. And in our Q&A of 5/17 (#Immunity), we talked about emerging evidence that “pre-existing SARS-CoV-2−crossreactive T cell responses were observed in healthy donors, indicating some potential for pre-existing immunity in the human population.” Since then, we have more information. Yay for science! Research results published three weeks ago in Nature, “SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls” and nicely synthesized in this Science commentary show three fascinating things:

  1. T-cells appear to be key to lasting immunity; T-cell immune response persists among recovering COVID-19 patients. Those study participants who are recovering from SARS-CoV-2 (COVID-19) (n=36) all had T-cells (CD4 helper and CD8 killer) indicating ongoing immunity to the virus. As speculated in the Science commentary, “T-cell driven immunity is perhaps the way to reconcile the apparent paradox between (1) antibody responses that seem to be dropping week by week in convalescent patients but (2) few (if any) reliable reports of actual re-infection.”
  2. Lasting immunity; T-cell immune response is long-lived among those recovered from SARS. Those who were infected with SARS-CoV-1 (e.g. SARS) have lasting immunity. 17 years(!) after SARS infection, all 23 study participants had a robust T-cell immune response. This bodes well for hopes of long-term immunity to SARS-CoV-2.
  3. Cross-reactive immunity; T-cells from SARS and other zoonotic coronaviruses are cross-reactive to SARS-CoV-2. Study participants who had recovered from SARS and a number of study participants who were never exposed to SARS or COVID have T-cells that are reactive to SARS-CoV-2! Interestingly, these T-cells do not react to proteins found in typical human coronaviruses, but instead react to those found typically in animal-based coronaviruses. Again, as posited in the Science commentary, “That would argue that there has been past zoonotic coronavirus transmission in humans, unknown viruses that apparently did not lead to serious disease, which have provided some people with a level of T-cell based protection to the current pandemic.”