Emergence of nonvaccine Streptococcus pneumoniae following a 13-valent pneumococcal conjugate vaccine and schedule change in Mozambique: implications for a national immunization strategy

Background In Mozambique, the introduction of a 13-valent pneumococcal conjugate vaccine (PCV13) using a two plus one schedule began in September 2019. However, the replacement of serotypes with non-PCV types remains a concern worldwide following widespread vaccination. We aim to describe the epidemiology of non-PCV13 types among children under 5 years of age with pneumococcal meningitis four years after PCV13 introduction in Mozambique. Methods Between January 2020 and December 2023, a total of 2,014 cerebrospinal fluid (CSF) samples were collected from eligible children as part of the meningitis surveillance system in Mozambique, 103 (5.1%) of which tested positive for S. pneumoniae after triplex qPCR. Among these, 86 (83.5%) samples met the quality criteria for serotyping and were subsequently analysed using sequential quadriplex qPCR. Results Among children under 2 years of age, 84.8% of the S. pneumoniae- positive samples belonged to non-PCV13 serotypes, with serotype 15B/C (31.0%) being the most prevalent, followed by 12F/12A/12B/44/46 (12.1%), 38B (10.6%), and 8 (7.6%). Serotypes 15B/C, 12F/12A/12B/44/46, 38, 8, and 1 were predominant in the northern region of the country (Nampula), whereas serotypes 15B/C and 12F/12A/12B/44/46 were most common in the central region (Sofala). The serotypes coverage of the PCV13, PCV15 and PCV20 vaccine formulations were 20.0%, 26.3% and 75.8%, respectively. Conclusion PCV13 vaccines save many lives in Mozambique. However, they do not seem to be adequate in addresing some of the highly prevailing non-PCV13 serotypes (15B/C and 12F/12A/12B/44/46). Therefore, we suggest that the country's National Immunization Technical Advisory Group (NITAG) review new data and advice on switching to extended valency vaccines such as PCV20.