A Comparison of Pneumococcal Nasopharyngeal Carriage in Very Young Fijian Infants Born by Vaginal or Cesarean Delivery

Importance Pneumococcal nasopharyngeal carriage is a prerequisite for pneumococcal disease. The main transmission route is from toddlers, who commonly carry pneumococci. However, neonatal pneumococcal disease case reports suggest that vertical pneumococcal transmission may also occur. Objective To describe and compare pneumococcal nasopharyngeal carriage and density by infant mode of delivery in young Fijian infants. Design, Setting, and Participants Annual cross-sectional surveys were performed in Suva, Fiji, before the introduction of 10-valent pneumococcal conjugate vaccine (PCV10), from September 14 to December 20, 2012, and after PCV10 was introduced, from July 11 to November 19, 2013; July 15 to December 9, 2014; and August 13 to November 19, 2015. Caregivers of 2006 infants aged 5 to 8 weeks participated in the surveys. Statistical analysis was performed from May 24, 2018, to August 12, 2019. Exposures Caregivers provided data on infant mode of delivery and demographics via interviewer-led survey. Main Outcomes and Measures Pneumococci in swab samples were detected and quantified bylytA quantitative polymerase chain reaction with molecular serotyping by microarray. Pneumococci were categorized as PCV10 or non-PCV10 serotypes. Results Of the 2006 infants (976 girls and 1030 boys; mean [SD] age, 6.1 [0.02] weeks]), 1742 (86.8%) were born vaginally and 264 were born by cesarean delivery. Infants delivered vaginally, compared with those born by cesarean delivery, had a higher prevalence of overall pneumococcal nasopharyngeal carriage (470 of 1722 [27.3%; 95% CI, 25.2%-29.4%] vs 47 of 260 [18.1%; 95% CI, 13.6%-23.3%];P = .002), PCV10 carriage (113 of 1698 [6.7%; 95% CI, 5.5%-7.9%] vs 8 of 256 [3.1%; 95% CI, 1.4%-6.1%];P = .03), and non-PCV10 carriage (355 of 1698 [20.9%; 95% CI, 19.0%-22.9%] vs 38 of 256 [14.8%; 95% CI, 10.7%-19.8%];P = .02), and had higher median densities of overall pneumococci (4.9 log10genome equivalents [GE]/mL [interquartile range, 4.8-5.0 log10GE/mL] vs 4.5 log10GE/mL [interquartile range, 4.1-4.6 log10GE/mL];P = .01) and non-PCV10 pneumococci (4.9 log10GE/mL [interquartile range, 4.7-5.0 log10GE/mL] vs 4.4 log10GE/mL [interquartile range, 4.0-4.7 log10GE/mL];P = .01). Vaginal delivery was associated with overall (adjusted odds ratio, 1.57 [95% CI, 1.10-2.23];P = .01) and non-PCV10 (adjusted odds ratio, 1.49 [95% CI, 1.01-2.20];P = .04]) pneumococcal nasopharyngeal carriage. Vaginal delivery was not associated with PCV10 carriage (adjusted odds ratio, 1.67 [95% CI, 0.80-3.51];P = .17). After adjustment, vaginal delivery was not associated with density. Conclusions and Relevance Pneumococcal nasopharyngeal carriage prevalence and density were higher in infants delivered vaginally compared with those delivered by cesarean birth. After adjustment, vaginal delivery was associated with pneumococcal carriage. Differences in carriage by mode of delivery may be due to differential exposure to the vaginal microbiota during delivery and the effect of intrapartum antibiotics during cesarean delivery on the infant microbiome. Our findings also raise the hypothesis that vertical transmission may contribute to pneumococcal acquisition.