This code system http://terminology.hl7.org/CodeSystem/allergyintolerance-verification defines the following codes:

LvlCodeDisplayDefinition
1unconfirmed UnconfirmedThe propensity for a reaction to the identified substance has not been objectively verified.
2  presumed PresumedThe available clinical information supports a high liklihood of the propensity for a reaction to the identified substance.
1confirmed ConfirmedThe propensity for a reaction to the identified substance has been objectively verified (which may include clinical evidence by testing, rechallenge, or observation).
1refuted RefutedA propensity for a reaction to the identified substance has been disputed or disproven with a sufficient level of clinical certainty to justify invalidating the assertion. This might or might not include testing or rechallenge.
1entered-in-error Entered in ErrorThe statement was entered in error and is not valid.
 <status value="draft"/> <experimental value="false"/> <date value="2022-09-14T03:23:03-06:00"/> <publisher value="FHIR Project team"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> </contact> <description value="The verification status to support or decline the clinical status of the allergy or intolerance."/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/allergyintolerance-verification"/> <content value="complete"/> <concept> <code value="unconfirmed"/> <display value="Unconfirmed"/> <definition value="The propensity for a reaction to the identified substance has not been objectively verified."/> <concept> <code value="presumed"/> <display value="Presumed"/> <definition value="The available clinical information supports a high liklihood of the propensity for a reaction to the identified substance."/> </concept> </concept> <concept> <code value="confirmed"/> <display value="Confirmed"/> <definition value="The propensity for a reaction to the identified substance has been objectively verified (which may include clinical evidence by testing, rechallenge, or observation)."/> </concept> <concept> <code value="refuted"/> <display value="Refuted"/> <definition value="A propensity for a reaction to the identified substance has been disputed or disproven with a sufficient level of clinical certainty to justify invalidating the assertion. This might or might not include testing or rechallenge."/> </concept> <concept> <code value="entered-in-error"/> <display value="Entered in Error"/> <definition value="The statement was entered in error and is not valid."/> </concept> </CodeSystem>