And if you remove this line
<option v-for="(symptom, id) in options" :key="id" :value="id">{{ symptom }}</option>
Do you then see the text?
I believe the reason is because on the default option which you've put selected to you don't have a value, and then there is a default value in your form.symptoms_1 property which does not match a no value option, will show as an empty dropdown.
So you make sure that you have value="" on your first option or -1 as a value, and then initialize the form.symptoms_1 to be either empty string or -1 whichever you chose.