diff --git a/src/ga4gh/vrs/extras/annotator/vcf.py b/src/ga4gh/vrs/extras/annotator/vcf.py
index 3d0d424f..ed5e4a92 100644
--- a/src/ga4gh/vrs/extras/annotator/vcf.py
+++ b/src/ga4gh/vrs/extras/annotator/vcf.py
@@ -34,12 +34,15 @@ class SeqRepoProxyType(str, Enum):
     REST = "rest"
 
 
-# Field names for VCF
-VRS_ALLELE_IDS_FIELD = "VRS_Allele_IDs"
-VRS_STARTS_FIELD = "VRS_Starts"
-VRS_ENDS_FIELD = "VRS_Ends"
-VRS_STATES_FIELD = "VRS_States"
-VRS_ERROR_FIELD = "VRS_Error"
+class FieldName(str, Enum):
+    """Define VCF field names for VRS annotations"""
+
+    IDS_FIELD = "VRS_Allele_IDs"
+    STARTS_FIELD = "VRS_Starts"
+    ENDS_FIELD = "VRS_Ends"
+    STATES_FIELD = "VRS_States"
+    ERROR_FIELD = "VRS_Error"
+
 
 # VCF character escape map
 VCF_ESCAPE_MAP = str.maketrans(
@@ -117,7 +120,7 @@ def annotate(
 
         vcf = pysam.VariantFile(filename=str(input_vcf_path.absolute()))
         vcf.header.info.add(
-            VRS_ALLELE_IDS_FIELD,
+            FieldName.IDS_FIELD.value,
             info_field_num,
             "String",
             (
@@ -126,7 +129,7 @@ def annotate(
             ),
         )
         vcf.header.info.add(
-            VRS_ERROR_FIELD,
+            FieldName.ERROR_FIELD.value,
             ".",
             "String",
             ("If an error occurred computing a VRS Identifier, the error message"),
@@ -134,7 +137,7 @@ def annotate(
 
         if vrs_attributes:
             vcf.header.info.add(
-                VRS_STARTS_FIELD,
+                FieldName.STARTS_FIELD.value,
                 info_field_num,
                 "String",
                 (
@@ -143,7 +146,7 @@ def annotate(
                 ),
             )
             vcf.header.info.add(
-                VRS_ENDS_FIELD,
+                FieldName.ENDS_FIELD.value,
                 info_field_num,
                 "String",
                 (
@@ -152,7 +155,7 @@ def annotate(
                 ),
             )
             vcf.header.info.add(
-                VRS_STATES_FIELD,
+                FieldName.STATES_FIELD.value,
                 info_field_num,
                 "String",
                 (
@@ -171,12 +174,12 @@ def annotate(
         vrs_data = {} if output_pkl_path else None
         for record in vcf:
             if vcf_out:
-                additional_info_fields = [VRS_ALLELE_IDS_FIELD]
+                additional_info_fields = [FieldName.IDS_FIELD]
                 if vrs_attributes:
                     additional_info_fields += [
-                        VRS_STARTS_FIELD,
-                        VRS_ENDS_FIELD,
-                        VRS_STATES_FIELD,
+                        FieldName.STARTS_FIELD,
+                        FieldName.ENDS_FIELD,
+                        FieldName.STATES_FIELD,
                     ]
             else:
                 # no INFO field names need to be designated if not producing an annotated VCF
@@ -195,8 +198,8 @@ def annotate(
                 _logger.exception("VRS error on %s-%s", record.chrom, record.pos)
                 err_msg = f"{ex}" or f"{type(ex)}"
                 err_msg = err_msg.translate(VCF_ESCAPE_MAP)
-                additional_info_fields = [VRS_ERROR_FIELD]
-                vrs_field_data = {VRS_ERROR_FIELD: [err_msg]}
+                additional_info_fields = [FieldName.ERROR_FIELD]
+                vrs_field_data = {FieldName.ERROR_FIELD.value: [err_msg]}
 
             _logger.debug(
                 "VCF record %s-%s generated vrs_field_data %s",
@@ -207,7 +210,9 @@ def annotate(
 
             if output_vcf_path and vcf_out:
                 for k in additional_info_fields:
-                    record.info[k] = [value or "." for value in vrs_field_data[k]]
+                    record.info[k.value] = [
+                        value or "." for value in vrs_field_data[k.value]
+                    ]
                 vcf_out.write(record)
 
         vcf.close()
@@ -287,7 +292,7 @@ def _get_vrs_object(
 
         if vrs_field_data:
             allele_id = vrs_obj.id if vrs_obj else ""
-            vrs_field_data[VRS_ALLELE_IDS_FIELD].append(allele_id)
+            vrs_field_data[FieldName.IDS_FIELD].append(allele_id)
 
             if vrs_attributes:
                 if vrs_obj:
@@ -301,16 +306,16 @@ def _get_vrs_object(
                 else:
                     start = end = alt = ""
 
-                vrs_field_data[VRS_STARTS_FIELD].append(start)
-                vrs_field_data[VRS_ENDS_FIELD].append(end)
-                vrs_field_data[VRS_STATES_FIELD].append(alt)
+                vrs_field_data[FieldName.STARTS_FIELD].append(start)
+                vrs_field_data[FieldName.ENDS_FIELD].append(end)
+                vrs_field_data[FieldName.STATES_FIELD].append(alt)
 
     def _get_vrs_data(
         self,
         record: pysam.VariantRecord,
         vrs_data: dict | None,
         assembly: str,
-        additional_info_fields: list[str],
+        additional_info_fields: list[FieldName],
         vrs_attributes: bool = False,
         compute_for_ref: bool = True,
         require_validation: bool = True,
@@ -333,7 +338,7 @@ def _get_vrs_data(
         :return: A dictionary mapping VRS-related INFO fields to lists of associated
             values. Will be empty if `create_annotated_vcf` is false.
         """
-        vrs_field_data = {field: [] for field in additional_info_fields}
+        vrs_field_data = {field.value: [] for field in additional_info_fields}
 
         # Get VRS data for reference allele
         gnomad_loc = f"{record.chrom}-{record.pos}"
@@ -356,7 +361,7 @@ def _get_vrs_data(
             if "*" in allele:
                 _logger.debug("Star allele found: %s", allele)
                 for field in additional_info_fields:
-                    vrs_field_data[field].append("")
+                    vrs_field_data[field.value].append("")
             else:
                 self._get_vrs_object(
                     allele,