Abstract
This study describes predictors of pneumococcal nasopharyngeal carriage and density in Fiji. We used data from four annual (2012-2015) cross-sectional surveys, pre- and post-introduction of ten-valent pneumococcal conjugate vaccine (PCV10) in October 2012. Infants (5-8 weeks), toddlers (12-23 months), children (2-6 years), and their caregivers participated. Pneumococci were detected and quantified using lytA qPCR, with molecular serotyping by microarray. Logistic and quantile regression were used to determine predictors of pneumococcal carriage and density, respectively. There were 8,109 participants. Pneumococcal carriage was negatively associated with years post-PCV10 introduction (global P<0.001), and positively associated with indigenous iTaukei ethnicity (aOR 2.74 [95% CI 2.17-3.45] P<0.001); young age (infant, toddler, and child compared with caregiver participant groups) (global P<0.001); urban residence (aOR 1.45 [95% CI 1.30-2.57] P<0.001); living with ≥2 children <5 years of age (aOR 1.42 [95% CI 1.27-1.59] P<0.001); low family income (aOR 1.44 [95% CI 1.28-1.62] P<0.001); and upper respiratory tract infection (URTI) symptoms (aOR 1.77 [95% CI 1.57-2.01] P<0.001). Predictors were similar for PCV10 and non-PCV10 carriage, except PCV10 carriage was negatively associated with PCV10 vaccination (0.58 [95% CI 0.41-0.82] P = 0.002) and positively associated with exposure to household cigarette smoke (aOR 1.21 [95% CI 1.02-1.43] P = 0.031), while there was no association between years post-PCV10 introduction and non-PCV10 carriage. Pneumococcal density was positively associated with URTI symptoms (adjusted median difference 0.28 [95% CI 0.16, 0.40] P<0.001) and toddler and child, compared with caregiver, participant groups (global P = 0.008). Predictors were similar for PCV10 and non-PCV10 density, except infant, toddler, and child participant groups were not associated with PCV10 density. PCV10 introduction was associated with reduced the odds of overall and PCV10 pneumococcal carriage in Fiji. However, after adjustment iTaukei ethnicity was positively associated with pneumococcal carriage compared with Fijians of Indian Descent, despite similar PCV10 coverage rates.
Highlights
Pneumococcal disease is a leading cause of childhood morbidity and mortality worldwide [1]
We found that prior to ten-valent pneumococcal conjugate vaccine (PCV10) introduction, iTaukei ethnicity was associated with increased odds of overall pneumococcal carriage in children aged 3–13 months [4]
We have reported that differences in social contact patterns by ethnicity partially account for higher prevalence of pneumococci among iTaukei, compared with Fijians of Indian Descent (FID), but that differences in carriage prevalence are likely related to ethnic differences in host or environmental factors [36]
Summary
Pneumococcal disease is a leading cause of childhood morbidity and mortality worldwide [1]. Determining factors associated with higher pneumococcal carriage density could aid estimation of pneumococcal pneumonia prevalence in childhood pneumonia studies [2]. Common factors positively associated with pneumococcal carriage in low- and middle-income countries include indigenous ethnicity, passive smoking; co-colonisation with Haemophilus influenzae, childcare attendance, poverty, acute respiratory infection, living with young children, and being under five years old [4, 8, 12]. In studies from low- and middle-income countries, higher pneumococcal density has been positively associated with the symptoms of upper respiratory tract infection, presence of a febrile acute respiratory infection in children [13], rainy season, severe pneumonia, viral coinfection, radiologically confirmed pneumococcal pneumonia, and encapsulated serotypes (compared with non-encapsulated serotypes) [2, 9,10,11, 13,14,15,16]
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