"During his first infection, my patient experienced a mild cough and sore throat," Dr.

Clay Ackerly explained in an opinion piece for Vox. "His second infection, in contrast, was marked by a high fever, shortness of breath, and hypoxia, resulting in multiple trips to the hospital.

"It is possible, but unlikely, that my patient had a single infection that lasted three months," Dr.

"My patient, however, cleared his infection — he had two negative PCR tests after his first infection — and felt healthy for nearly six weeks.".

Typically, experts estimate that between 70 and 90 percent of a population must be immune to a contagious disease to achieve herd immunity -- whether through vaccination or other exposure to an infection.

Typically, at least 70 percent of a population must be immune to achieve herd immunity.

"Infection tends to give you the best-case scenario for an antibody response, so if your infection is giving you antibody levels that wane in two to three months, the vaccine will potentially do the same thing,” Dr.