The COVID−19 pandemic has been going on for three years, and research on preventive and curative measures is continuously being made. Belonging to the same coronavirus family, human common cold coronaviruses (CCCs) like 229E, NL63, HKU1, and OC43 have been around for decades. However, unlike SARS−CoV−2, they do not manifest serious signs and symptoms. Reports on T−cell cross−reactivit…