Immunity
Immunization
noun
To excuse yourself from the epidemic, you'll have to have immunity or immunization from the disease.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
いつも微熱とひどい頭痛があるのでお医者さんに行ったら、免疫機能が弱ってきていると言われました。
I went to the doctor because I always have a slight fever and terrible headache, and I was told that my immune system is weakening.