The impact of introduction of the 10-valent pneumococcal conjugate vaccine (PCV10) on pneumococcal carriage in Nigeria

Abstract

Background Pneumococcal Conjugate Vaccines (PCVs) reduce the burden of pneumococcal disease by reducing nasopharyngeal acquisition and transmission of serotypes in the vaccines (vaccine-serotypes). Following introduction of the 10-valent PCV (PCV10) in Nigeria, we assessed the population-level impact of PCV introduction on pneumococcal carriage. Methods We conducted annual cross-sectional carriage and vaccination coverage surveys between 2016 and 2020 in rural and urban sites in Nigeria. We recruited a random sample of residents and used WHO-recommended laboratory methods to identify pneumococcal serotypes. We modelled prevalence ratios for the change in annual carriage prevalence using log-binomial regression, and explored the association between vaccination coverage in children <5 years and changes in the population-level vaccine-serotype carriage over time. Findings We enrolled 4,684 and 3,653 participants for the carriage surveys and 2,135 and 1,106 children for the coverage surveys in the rural and urban sites, respectively. Carriage prevalence of vaccine-serotypes declined steadily with increasing levels of PCV10 coverage among children aged <5 years. From 2016 to 2020, coverage with three doses of PCV10 increased from 7% to 59% and from 15% to 81% in the rural and urban sites, respectively. Prevalence ratios for the annual change in vaccine-serotype carriage in participants aged <5 years and ≥5 years were 0.84 (95% CI:0.79-0.89) and 0.86 (95%CI:0.80-0.89) in the rural, and 0.69 (95% CI:0.62-0.77), and 0.83 (95% CI:0.74-0.93) in the urban sites. Interpretation We found significant reduction in vaccine-serotype carriage at a population level following a steady increase in PCV10 coverage, indicating direct and indirect vaccine effects.

Changes in pneumococcal serotypes distribution and penicillin resistance in healthy children five years after generalization of PCV10

“…In this study, the most commonly detected NVSs were serotypes: 6C/6D, 19B/19C, and 15B/15C. The prevalence of these serotypes follows the changes reported in studies conducted in Bangladesh [ 35 ], the Netherlands [ 36 ], and Nigeria [ 37 ] following the introduction of PCV10. Additionally, the carriage of serotype 15 is known to be more prevalent in the PCV era [ 38 ].…”

Evaluation of statistical models of carriage to predict the impact of the 10-valent pneumococcal conjugate vaccine on invasive pneumococcal disease in Nigeria

“…VT carriage was not eliminated; indeed, VT carriage prevalence at the end of the introduction period was 22% in the rural area and 12% in urban area. (22) In HICs, VT carriage elimination was relatively rapid and complete after PCV7 introduction (27,28) supporting the use of this simple model. By contrast, PCV13 has not eliminated the extra-non-PCV7 serotypes in HICs.…”

“…This effect is likely to be small because no formal catch-up was offered to older children when PCV10 was introduced, and we previously estimated that, at the time of the baseline survey, the coverage of two doses of PCV10 among all children aged <5 years was only 7% in the rural site and 15% in the urban site (see also Table S1). (22) In conclusion, Model 1 makes a strong assumption about eliminating VT carriage, which has not been born out in the Nigerian setting examined. However, the intent of the model is not to predict exact PCV impact but rather to give an assessment on the…”

“…(21) As PCV10 (GSK) was introduced without a catchup campaign and as uptake was relatively modest, we estimated only a small percentage (7-15%) of children aged <5 years were vaccinated at the time of the baseline surveys, and therefore this could represent pre-vaccine epidemiology (22). In the post-vaccine period, we conducted four (2017-2020) annual carriage surveys in the rural site and three (2018-2020) in the urban site (22).…”

Pneumococcal population genomics changes during the early time period of conjugate vaccine uptake in southern India

“…Following the rollout of the universal immunization programme of 2017 in India, the WHO estimated nationwide population coverage of PCV of 6 % in 2018, 15 % in 2019 and 21% in 2020 [47]. This level of coverage is below what has been observed in some low-and middle-income countries to result in reduced rates of VT carriage and follow-on invasive disease [48].…”