Is covid19 reinfection (with same or a new variant) a rare phenomenon? for how long is a recovered patient protected against reinfection? if it occurs, will the symptoms be milder than the primary infection?

Reinfection in a previously infected or vaccinated person is rare, even with variant strains. The reinfection is usually asymptomatic and serious illness or death is virtually non-existent. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.