deusthindwa/spn.hhtransmission.dynamic.model.malawi

# Transmission routes of pneumococcus after a longstanding 13-valent infant conjugate vaccination program in Malawi: A mathematical modelling study Non-vaccine serotypes (NVT) and vaccine serotypes (VT) continuously predispose adults with human immunodeficiency virus (HIV) on antiretroviral therapy (ART) and younger children to elevated risk of pneumococcal disease. We aimed to identify pneumococcal household transmission routes after 15-years of using infant pneumococcal conjugate vaccine (PCV13) in Malawi. We collected weekly longitudinal nasopharyngeal swabs from members in random households. We detected pneumococcus using microbiological culture and serotyped using latex agglutination. We fitted a household dynamic model to trajectories of carriage in a Bayesian framework and inferred the transmission parameters from the posterior distribution. 906 samples were collected across three visits from 302 participants; younger children (0-5 years-old [y]), older children (6-17y), and adults (18+y) without HIV, on short-term ( 1 year) ART. Carriage prevalence was higher for NVT (range: 42.4-47.7%) than VT (10.3-11.6%). Within household, adults on long-term ART disproportionately transmitted VT to younger children whereas younger children had multiple routes to transmit NVTs; to agemates, to older children, and to adults on long-term ART. As key infectors, both adults on long-term ART and younger children were characterised with prolonged carriage. NVT had a larger share of total force of infection due to widespread use of infant PCV13. Exposure to NVT was evenly shared across household and community and to VT was mostly within household. To further reduce colonisation and subsequent disease, extended-valency and targeted PCVs strategies among toddlers/preschool children and adults on ART are needed. Keywords: Mathematical model, Transmission routes, Force of infection, Pneumococcal clearance, Pneumococcal competition, Malawi.