Abstract
BackgroundIntroduction of pneumococcal vaccines in Nigeria is a priority as part of the Accelerated Vaccine Introduction Initiative (AVI) of the Global Alliance for Vaccines and Immunisation (GAVI). However, country data on the burden of pneumococcal disease (IPD) is limited and coverage by available conjugate vaccines is unknown. This study was carried out to describe the pre vaccination epidemiology and population biology of pneumococcal carriage in Nigeria.MethodsThis was a cross sectional survey. Nasopharyngeal swabs (NPS) were obtained from a population sample in 14 contiguous peri-urban Nigerian communities. Data on demographic characteristics and risk factor for carriage were obtained from all study participants. Pneumococci isolated from NPS were characterised by serotyping, antimicrobial susceptibility and Multi Locus Sequencing Typing (MLST).ResultsThe prevalence of pneumococcal carriage was 52.5%. Carriage was higher in children compared to adults (67.4% vs. 26%), highest (≈90%) in infants aged <9 months and reduced significantly with increasing age (P<0.001). Serotypes 19F (18.6%) and 6A (14.4%) were most predominant. Potential vaccine coverage was 43.8%, 45.0% and 62% for PCV-7, PCV-10 and PCV-13 respectively. There were 16 novel alleles, 72 different sequence types (STs) from the isolates and 3 Sequence Types (280, 310 and 5543) were associated with isolates of more than one serotype indicative of serotype switching. Antimicrobial resistance was high for cotrimoxazole (93%) and tetracycline (84%), a third of isolates had intermediate resistance to penicillin. Young age was the only risk factor significantly associated with carriage.ConclusionsPneumococcal carriage and serotype diversity is highly prevalent in Nigeria especially in infants. Based on the coverage of serotypes in this study, PCV-13 is the obvious choice to reduce disease burden and prevalence of drug resistant pneumococci. However, its use will require careful monitoring. Our findings provide sound baseline data for impact assessment following vaccine introduction in Nigeria.
Highlights
Pneumonia is one of the leading causes of mortality in children,5 years old
We investigated pneumococcal carriage in a Nigerian population to determine carriage rates, prevalent serotypes; theoretical coverage of pneumococcal conjugate vaccines and molecular epidemiology of pneumococci in this population
Study area and population The Lagos University Teaching Hospital Primary Health Care and Rural Medicine Centre (LUTH PHC), Pakoto village is approximately 70 kilometres from Lagos, Nigeria. This health centre serves all communities within a 10 km radius covering two local government areas (LGAs) and it was the base for this study
Summary
Pneumonia is one of the leading causes of mortality in children ,5 years old. It is responsible for 1.6 million of 8.8 million annual deaths in this age group [1] with 50% occurring in subSaharan Africa [2]. Pneumococcus is a major cause of acute otitis media (AOM), bacteraemia, meningitis and sinusitis in developing countries [5]. There are over 91 serotypes of pneumococci and worldwide, 6– 11 serotypes are responsible for $70% of invasive disease (IPD) in children ,5 years old [6]. Pneumococcal carriage is highly prevalent in developing countries among children aged ,5 years.
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