Professor Yuen Kwok-yung from HKU's Department of Microbiology discussed the world's first case of COVID-19 reinfection in an interview. He mentioned that reinfection is possible, especially if the first infection was mild. The immunity may go down rapidly, leading to a second infection. Vaccination may still be necessary for those who have had COVID-19 to ensure prolonged protection. People who have recovered from the infection should continue to practice safety measures like wearing masks, maintaining hand hygiene, and social distancing.