@DrEricDing How does anyone know that it is a "small fraction" after 3rd, 4th or later infections?
@Drericing：在第三次、第四次或以后的感染后，人们怎么知道这是一个“小部分”？
@DrEricDing How does anyone know that it is a "small fraction" after 3rd, 4th or later infections?
@Drericing：在第三次、第四次或以后的感染后，人们怎么知道这是一个“小部分”？