This is the ValueSet that contains all the codes in WHO Test Result (COVID-19) (http://smart.who.int/ddcc/ValueSet/who-ddcc-test-result-covid-19) and WHO Test Result (COVID-19) (http://smart.who.int/ddcc/ValueSet/who-ddcc-test-result-covid-19). E.g. what you have to deal with if you get resources containing codes in either of them