pill – n. a usually medicinal or dietary preparation in a small rounded mass to be swallowed whole

annually – adv. once a year : each year

expensive – adj. costing a lot of money

adherence – n. the act of doing what is required by

symptom – n. a change in the body or mind which indicates that a disease is present

variant – n. strains of a disease

challenging – adj. testing one's ability, endurance, etc: