Nasopharyngeal carriage of Streptococcus pneumoniae in children under 5 years of age before introduction of pneumococcal vaccine (PCV10) in urban and rural districts in Pakistan

Abstract

BackgroundBenefits of pneumococcal conjugate vaccine programs have been linked to the vaccine’s ability to disrupt nasopharyngeal carriage and transmission. The 10-valent pneumococcal vaccine (PCV10) was included in the Expanded Program on Immunization (EPI) in Sindh, Pakistan in February 2013. This study was carried out immediately before PCV10 introduction to establish baseline pneumococcal carriage and prevalent serotypes in young children and to determine if carriage differed in urban and rural communities.MethodsNasopharyngeal specimens were collected from a random sample of children 3-11 and 12-59 months of age in an urban community (Karachi) and children 3-11 months of age in a rural community (Matiari). Samples were processed in a research laboratory in Karachi. Samples were transported in STGG media, enriched in Todd Hewitt broth, rabbit serum and yeast extract, cultured on 5% sheep blood agar, and serotyped using the CDC standardized sequential multiplex PCR assay. Serotypes were categorized into PCV10-type and non-vaccine types.ResultsWe enrolled 670 children. Pneumococci were detected in 73.6% and 79.5 % of children in the infant group in Karachi and Matiari, respectively, and 78.2% of children 12 to 59 months of age in Karachi. In infants, 38.9% and 33.5% of those carrying pneumococci in Karachi and Matiari, respectively, had PCV10 types. In the older age group in Karachi, the proportion was 30.7%, not significantly different from infants. The most common serotypes were 6A, 23F, 19A, 6B and 19F.ConclusionWe found that about 3 of 4 children carried pneumococci, and this figure did not vary with age group or urban or rural residence. Planned annual surveys in the same communities will inform change in carriage of PCV10 serotype pneumococci after the introduction and uptake of PCV10 in these communitiesElectronic supplementary materialThe online version of this article (10.1186/s12879-018-3608-5) contains supplementary material, which is available to authorized users.

Pneumococcal nasopharyngeal carriage among Bhutanese children hospitalized with clinical pneumonia: serotypes and viral co-infection

“…This serotype distribution is rather different from that described in similar studies. We found a much higher proportion of children with the serotype 7B/7C/40, while the proportion of children we identified with the serotypes 19F, 6A or 6B was considerably lower than in similar studies (proportion of serotypes in children sick with respiratory symptoms) [7,17,41,42,44] or among healthy children in communitybased carriage studies [43,[45][46][47][48]. In the neighbouring context of India, 6A/B and 19F were also found to be the most prevalent serotypes in children admitted with clinical pneumonia, together with serotypes 14 and 23F.…”

Pneumococcal carriage, density, and co-colonization dynamics: A longitudinal study in Indonesian infants

“…We previously reported a pneumococcal carriage prevalence of 64% in children aged 12-24 months old in the Bandung region, suggesting that carriage rates stabilize after 12 months in this population (Dunne et al, 2018). Carriage prevalence tended to be higher in infants living in semi-rural areas than in urban residents, as observed in some, but not all, other studies (Hanieh et al, 2014;Nisar et al, 2018). Previously, we did not observe differences in pneumococcal carriage between urban and semi-rural Indonesian children aged 12-24 months, suggesting that differences diminish with age (Fadlyana et al, 2018).…”

Direct and indirect effect of 10 valent pneumococcal vaccine on nasopharyngeal carriage in children under 2 years of age in Matiari, Pakistan

“…We looked at indirect effect in two ways- first in the form of decline in the unvaccinated group over the course of four years. Secondly, we calculated a more formal measure of indirect effect by comparing VT carriage in the unvaccinated group (0 dose) with the pre-introduction VT carriage [14] . This is a slightly different approach from other studies reported in literature where the comparison is made usually with the adult population, older children or the group too young to be vaccinated or a concurrent population where the vaccine has not been introduced.…”

“…In this paper, we aim to describe impact of PCV10 on pneumococcal carriage in vaccinated (direct protection) and unvaccinated children (indirect or herd protection) aged less than two years in a rural population in Matiari, Sindh, Pakistan. We use point estimate of 26.7% as the baseline Vaccine Type (VT) carriage from a pre-introduction carriage survey in the same population [14] . We also describe the socio-demographic and clinical characteristics associated with VT carriage.…”