Safety and immunogenicity of 13-Valent pneumococcal conjugate vaccine in healthy infants in Shanghai during the COVID-19 pandemic: a prospective cohort study.

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae) is a major cause of morbidity and mortality in infants, leading to diseases like pneumonia and otitis media. Although the World Health Organization (WHO) recommends inclusion of pneumococcal conjugate vaccines (PCVs) in national immunization programs, 13-Valent PCV (PCV13) remains optional in China, with suboptimal coverage, especially in urban settings like Shanghai. This study was performed to evaluate the safety, immunogenicity and impact on nasopharyngeal carriage of S. pneumoniae of PCV13 in healthy infants in Shanghai.

MATERIAL AND

METHODS

A prospective cohort study was conducted from 2021 to 2023 in Shanghai. Cohort 1 (n=146) assessed immunogenicity and carriage, with infants receiving a 2 + 1 + 1 PCV13 series or no pneumococcal vaccine. Cohort 2 (n=114) assessed safety. Immunogenicity was assessed through serotype-specific IgG concentrations determined by ELISA, expressed as geometric mean concentrations (GMCs). Pneumococcal carriage was evaluated using nasopharyngeal swabs, with serotyping performed by multiplex real-time PCR. One-way repeated-measures ANOVA to compare the IgG GMCs in vaccinated group at three different time points.

RESULTS

In Cohort 1, 69.86% of vaccinated infants completed the 1-year follow-up. Carriage rates were 5.80% in the vaccinated group versus 6.45% in controls one month after the third dose (P = 1.00), and 3.92% versus 13.21% one year after the fourth dose (P = 0.161). IgG GMCs increased significantly from baseline to one month after the third dose (mean difference: 6.41 μg/mL, 95% CI: 5.43-7.39, P<0.001) and to one year after the fourth dose (mean difference: 12.01 μg/mL, 95% CI: 11.28-12.74, P<0.001). In Cohort 2, six infants reported mild adverse events, but no serious events or deaths were noted.

CONCLUSION

PCV13 induced strong immunogenicity and showed a favorable safety profile, with a non-significant trend toward reduced pneumococcal carriage. These findings provide real-world evidence from Shanghai and support further evaluation of PCV13 in broader cohorts.