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Is previous coronavirus infection protective against COVID-19?

Question: Have you come across any data suggesting previous infection with the 2003 SARS virus is protective against SARS-CoV 2?

Answer: As it turns out, we explored this issue way back in a Q&A of 8/6/2020!  Way back 1.5 years ago, initial scientific findings indicated that there could be some protection against SARS-CoV-2 afforded from previous coronavirus infection, including infection from SARS-CoV-1.  Since then, more evidence has accumulated showing that the T-cells developed from previous coronavirus infection could provide some protection against SARS-CoV-2 (and other coronavirus infections).  Here are a few nuggets, from newest to oldest:

  1. Cross-reactive memory T cells associate with protection against SARS-CoV-2 infection in COVID-19 contacts. This real-world, observational study published by Nature in January 2022 suggests that pre-existing T cells developed from previous coronavirus infection may provide protection against SARS-CoV-2.  Results are nicely synthesized by MedicalNewsToday.  This study also supports the need for vaccine development to focus beyond the spike protein to include non-spike targets.
  2. Decades-old SARS virus infection triggers potent response to COVID vaccines. This report published by Nature in August 2021 describes the results of a recent NEJM published study among other updates, indicating that a pan-coronavirus vaccine is possible.  “People who were infected almost two decades ago with the virus that causes severe acute respiratory syndrome (SARS) generate a powerful antibody response after being vaccinated against COVID-19. Their immune systems can fight off multiple SARS-CoV-2 variants, as well as related coronaviruses found in bats and pangolins…. the results offer hope that vaccines can be developed to protect against all new SARS-CoV-2 variants, as well as other coronaviruses that have the potential to cause future pandemics.”    
  3. Antibody response to SARS-CoV-2 infection inhumans: A systematic review.  This synthesis published by PlosOne in December 2020 finds that “Cross-reactive antibody-binding responses appear to be highest between SARS-CoV-1 and SARS-CoV-2, however cross-neutralisation is rare and where reported is weak.”  In lay terms, this means that antibodies developed in response to SARS-CoV-1 have been found to respond to SARS-CoV-2, but rarely to the degree required to curtail viral reproduction/infectivity. (note: these findings were collected pre-COVID vaccine and were largely based on lab-based tests)