This is a HL7 FHIR server, and as you appear to be accessing this page from a web browser you are seeing a HTML version of the requested resource(s). You can also access this URL from a FHIR client as a ReSTful API call. For more details please see the HL7 FHIR specification.
<CodeSystem xmlns="http://hl7.org/fhir">
<id value="CareConnect-ImmunizationExplanationReason-1"></id>
<text>
<status value="generated"></status>
</text>
<url value="https://fhir.hl7.org.uk/STU3/CodeSystem/CareConnect-ImmunizationExplanationReason-1"></url>
<version value="1.0.0"></version>
<name value="Care Connect Immunization Explanation Reason"></name>
<status value="draft"></status>
<date value="2018-05-03T00:00:00+00:00"></date>
<publisher value="HL7 UK"></publisher>
<description value="A CodeSystem that identifies a code to record the reason why a vaccine was administered."></description>
<copyright value="Copyright © 2016 HL7 UK"></copyright>
<content value="complete"></content>
<concept>
<code value="1"></code>
<display value="Routine mass immunisation"></display>
</concept>
<concept>
<code value="2"></code>
<display value="Travel to endemic area"></display>
</concept>
<concept>
<code value="3"></code>
<display value="Planned travel to high risk area"></display>
</concept>
<concept>
<code value="4"></code>
<display value="Recent travel to high risk area"></display>
</concept>
<concept>
<code value="5"></code>
<display value="Subpopulation at special or unusual risk"></display>
</concept>
<concept>
<code value="6"></code>
<display value="High risk due to occupation"></display>
</concept>
<concept>
<code value="7"></code>
<display value="High risk due to lifestyle"></display>
</concept>
<concept>
<code value="8"></code>
<display value="High risk due to existing medical condition"></display>
</concept>
<concept>
<code value="9"></code>
<display value="Control of known sporadic outbreak"></display>
</concept>
<concept>
<code value="10"></code>
<display value="Patient request"></display>
</concept>
<concept>
<code value="11"></code>
<display value="Post-exposure prophyaxis"></display>
</concept>
<concept>
<code value="12"></code>
<display value="Other"></display>
</concept>
</CodeSystem>