There are many limitations in evaluating vaccine efficacy by comparing the incidence of clinical endpoint events (such as morbidity, bacterial colonization) between the vaccine group and the control group. Therefore, the researchers put forward the concept of Surrogate of protection to predict vaccine protection with immunological indicators. In 2012, WHO put forward the immunological substitution endpoint of pneumococcal vaccine, using 0. 35 μg/ml as the protective antibody level of pneumococcal vaccine. But subsequent studies have found that using this threshold to assess all vaccine serotypes may not be accurate.

Pneumococcal infections; Vaccine; Surrogate of protection