Direct and indirect effects of 13-valent pneumococcal conjugate vaccine on pneumococcal carriage in children hospitalised with pneumonia from formal and informal settlements in Mongolia: an observational study

Abstract

Background: Within Ulaanbaatar, Mongolia, risk factors for pneumonia are concentrated among children living in informal settlements comprised of temporary shelters (gers). We used pneumococcal carriage surveillance among children from formal and informal settlements hospitalised with pneumonia to evaluate the direct and indirect effects of 13-valent pneumococcal conjugate vaccine (PCV13) against vaccinetype (VT) pneumococcal carriage following a phased introduction of PCV13.Methods: We enrolled and collected nasopharyngeal swabs from children 2-59 months of age presenting to hospital. Pneumococci were detected using lytA qPCR and serotyped using microarray on a random monthly selection of swabs between November 2015 and March 2019 from two districts in Ulaanbaatar. PCV13 status was determined using written records. We quantified the associations between individual PCV13 status (direct effects) and district-level PCV13 coverage (indirect effects) and VT carriage using generalised estimating equations and explored interactions by settlement type.Findings: A total of 1 292 swabs from 6 046 participants were tested for pneumococci. Receipt of PCV13 and increasing PCV13 coverage independently reduced the risk of VT carriage. For each percent increase in PCV13 coverage, the adjusted odds of VT carriage decreased by 1 • 0% (OR 95% CI 0 • 983-0 • 996; p = 0 • 001), with a predicted decrease in VT carriage rate from 29 • 1% to 13 • 1% as coverage reached 100%. There was a trend towards a slower decline within informal settlements (p = 0 • 100). Adjusted PCV13 vaccine effectiveness against VT carriage was 39 • 1% (95% CI 11 • 4-58 • 1%, p = 0 • 009).

Effect of Pneumococcal Conjugate Vaccine on Pneumonia Incidence Rates among Children 2–59 Months of Age, Mongolia, 2015–2021

“…Movement between districts and migration may also have varied over the study period. A previous publication from Mongolia found evidence of direct and indirect vaccine effects on carriage, which varied by formal and informal living conditions ( 32 ). We observed a reduction (46%) in vaccine-type pneumococcal carriage 3–5 years after introduction in 4 districts.…”

Streptococcus pneumoniae serotype 33G: genetic, serological, and structural analysis of a new capsule type

“…In Mongolia, the 13-valent Pneumococcal Conjugate Vaccine (PCV13) was introduced into the pediatric immunization program in a 2 + 1 schedule (2, 4, and 9 months of age) in a phased manner across districts of the capital city, Ulaanbaatar, from 2016 to 2018. In 2016 and 2017, three of the districts (Songinokhairkhan, Sukhbaatar, and Bayanzurkh) had a catch-up campaign for children aged 3–23 months (two doses given 2 months apart), followed by nationwide introduction with high coverage ( 19 , 20 ). Pneumococcal surveillance included the collection of nasopharyngeal swabs from healthy children (cross-sectional surveys in 2015, 2017, and 2022) ( 21 ) as well as children (2015–2021) and adults (2019–2022) hospitalized with pneumonia ( 20 , 22 , 23 ) as part of studies assessing the direct and indirect impact of PCV13.…”

“…In 2016 and 2017, three of the districts (Songinokhairkhan, Sukhbaatar, and Bayanzurkh) had a catch-up campaign for children aged 3–23 months (two doses given 2 months apart), followed by nationwide introduction with high coverage ( 19 , 20 ). Pneumococcal surveillance included the collection of nasopharyngeal swabs from healthy children (cross-sectional surveys in 2015, 2017, and 2022) ( 21 ) as well as children (2015–2021) and adults (2019–2022) hospitalized with pneumonia ( 20 , 22 , 23 ) as part of studies assessing the direct and indirect impact of PCV13. Nasopharyngeal swabs ( n = 12,850) were screened for pneumococci using quantitative PCR (qPCR) targeting the lytA gene ( 24 ).…”

Streptococcus pneumoniaeserotype 33G: genetic, serological, and structural analysis of a new capsule type

“…In Mongolia, the 13-valent Pneumococcal Conjugate Vaccine (PCV13) was introduced into the paediatric immunization program in a 2+1 schedule (2, 4 and 9 months of age) in a phased manner across districts of the capital city, Ulaanbaatar, from 2016-2018. In 2016 and 2017, three of the districts (Songinokhairkhan, Sukhbaatar and Bayanzurkh) had a catch-up campaign for children aged 3 to 23Cmonths (two doses given two months apart), followed by nation-wide introduction with high coverage (19, 20). Pneumococcal surveillance included the collection of nasopharyngeal swabs from healthy children (cross-sectional surveys in 2015, 2017 and 2022) (21) as well as children (2015–2021) and adults (2019–2022) hospitalized with pneumonia (20, 22, 23) as part of studies assessing the direct and indirect impact of PCV13.…”

“…In 2016 and 2017, three of the districts (Songinokhairkhan, Sukhbaatar and Bayanzurkh) had a catch-up campaign for children aged 3 to 23Cmonths (two doses given two months apart), followed by nation-wide introduction with high coverage (19, 20). Pneumococcal surveillance included the collection of nasopharyngeal swabs from healthy children (cross-sectional surveys in 2015, 2017 and 2022) (21) as well as children (2015–2021) and adults (2019–2022) hospitalized with pneumonia (20, 22, 23) as part of studies assessing the direct and indirect impact of PCV13. Nasopharyngeal swabs (n=12,850) were screened for pneumococci using quantitative PCR (qPCR) targeting the lytA gene (24).…”