Effectiveness of ten-valent pneumococcal conjugate vaccine on invasive pneumococcal disease among children <2 years old: A prospective population-based study in rural Bangladesh

The 10-valent pneumococcal conjugate vaccine (PCV10) was introduced in March 2015 in Bangladesh. In this study, we aimed to estimate the impact of PCV10 on invasive pneumococcal disease (IPD) identified by blood cultures and severe pneumonia identified clinically and its effectiveness on invasive disease caused by vaccine serotypes. We conducted population-based surveillance among children aged 2- <24 months between April 2012 through March 2019 in Mirzapur, a rural sub-district of Bangladesh. We compared incidence of IPD and severe pneumonia before (April 2012 to March 2015) and after (April 2015 to March 2019) the introduction of PCV10. Vaccine effectiveness was measured using an indirect cohort analysis of data from four sentinel sites in which PCV10 vaccination status was compared between children with IPD caused by vaccine serotype vs. non-vaccine serotypes. We identified 24 IPD cases by blood culture and 1,704 severe pneumonia hospitalizations during the surveillance period. IPD incidence in under-2-year-old children fell 25 % (95 % CI: -1.2 % to 76 %; p-value = 0.59) from 106 cases per 100,000 child-years at baseline to 79.3 in April 2018- March 2019. Vaccine serotype-IPD incidence was lower (77 % reduction, 95 % CI: -0.45 % to 96 %; p-value = 0.068) in April 2018 - March 2019 than in the pre-vaccine period (85.7 cases to 19.8/100,000 child-years). A significant decline of 54.0 % (95 % CI: 47.0 % to 59.0 %; p-value < 0.001) was observed in hospitalizations due to severe pneumonia. From indirect cohort analysis, the effectiveness of PCV10 against vaccine serotype IPD was 37 % (95 % CI: -141.0 % to 83.5 %; p = 0.5) after the 1st dose and 63.1 % (95 % CI: -3.3 % to 85.9 %, p = 0.0411) after the 2nd or the 3rd dose. This study demonstrates that PCV10 introduction prevented hospitalizations with severe pneumonia and provided individual protection against vaccine serotypes.