Abstract
BACKGROUND: To understand the immunogenicity and safety of the 23-valent pneumococcal polysaccharide vaccine in elderly individuals aged 60-70 years in Shanghai after revaccination. METHODS: A total of 330 elderly people aged 60-70 years were recruited to study the immunogenicity and safety of PPSV23 revaccination. The group with a history of PPSV23 vaccination and an interval of 5 years or more was selected as the revaccination group (n=220), and the group without any pneumococcal vaccine was selected as the first vaccination group (n=110). RESULTS: In terms of immunogenicity, the GMCs of all serotypes before and after immunization were 1.15-21.57 µg/ml and 1.62-33.19 µg/ml, respectively, in the revaccination group, and the GMCs of all serotypes after immunization were higher than those before immunization (P<0.0001). After immunization, the total GMI of antibodies in the revaccination group was lower than that in the first vaccination group [1.62(1.57, 1.67) vs 3.20(2.82, 3.57), P<0.0001], and the GMIs of all serotypes in the revaccination group were also lower than those in the first vaccination group [(1.40-1.92) vs (1.82-4.69), P<0.0001]. In terms of safety, no serious adverse events occurred during the study and all adverse events that occurred were mild or self-limiting. From 0-30 days after immunization, 7 patients in the revaccination group and 14 patients in the first vaccination group experienced adverse events, with incidence rates of 3.18% and 12.73%, respectively, which were lower in the revaccination group than in the first vaccination group (P=0.0008). CONCLUSIONS: Compared with those before vaccination, the antibody levels of elderly people aged 60-70 years in Shanghai who were inoculated with PPSV23 for 5 years or more tended to increase but were lower than those in the first vaccination group. The safety of revaccination with PPSV23 was favorable. CLINICAL TRIAL REGISTRATION: http://www.chictr.org.cn, identifier ChiCTR2100042000; http://clinicaltrials.gov, identifier NCT04701788.