Impact of the introduction of pneumococcal conjugate vaccination on invasive pneumococcal disease and pneumonia in The Gambia: 10 years of population-based surveillance

Abstract

Background The Gambia introduced seven-valent pneumococcal conjugate vaccine (PCV7) in August 2009, followed by PCV13 in May, 2011, using a schedule of three primary doses without a booster dose or catch-up immunisation. We aimed to assess the long-term impact of PCV on disease incidence. MethodsWe did 10 years of population-based surveillance for invasive pneumococcal disease (IPD) and WHO defined radiological pneumonia with consolidation in rural Gambia. The surveillance population included all Basse Health and Demographic Surveillance System residents aged 2 months or older. Nurses screened all outpatients and inpatients at all health facilities using standardised criteria for referral. Clinicians then applied criteria for patient investigation. We defined IPD as a compatible illness with isolation of Streptococcus pneumoniae from a normally sterile site (cerebrospinal fluid, blood, or pleural fluid). We compared disease incidence between baseline (May 12, 2008-May 11, 2010) and post-vaccine years (2016-2017), in children aged 2 months to 14 years, adjusting for changes in case ascertainment over time.Findings We identified 22 728 patients for investigation and detected 342 cases of IPD and 2623 cases of radiological pneumonia. Among children aged 2-59 months, IPD incidence declined from 184 cases per 100 000 person-years to 38 cases per 100 000 person-years, an 80% reduction (95% CI 69-87). Non-pneumococcal bacteraemia incidence did not change significantly over time (incidence rate ratio 0•88; 95% CI, 0•64-1•21). We detected zero cases of vaccine-type IPD in the 2-11 month age group in 2016-17. Incidence of radiological pneumonia decreased by 33% (95% CI 24-40), from 10•5 to 7•0 per 1000 person-years in the 2-59 month age group, while pneumonia hospitalisations declined by 27% (95% CI 22-31). In the 5-14 year age group, IPD incidence declined by 69% (95% CI -28 to 91) and radiological pneumonia by 27% (95% CI -5 to 49).Interpretation Routine introduction of PCV13 substantially reduced the incidence of childhood IPD and pneumonia in rural Gambia, including elimination of vaccine-type IPD in infants. Other low-income countries can expect substantial impact from the introduction of PCV13 using a schedule of three primary doses.

Pneumococcal conjugate vaccination in The Gambia: health impact, cost effectiveness and budget implications

“…[5][6][7] The incidence of invasive pneumococcal disease in children younger than 5 years of age declined by 80%, from 184 to 38 cases per 100 000 person-years and pneumonia hospitalisation declined by 27%, from 43 to 32 cases per 1000 person-years. 8 Empiric data on the impact of PCV programmes in Africa are also available from Kenya as well as other countries around the world. 9 10 To date, 60 low-income and middle-income countries have introduced PCV into their national immunisation programmes with support from Gavi, the Vaccine Alliance (Gavi).…”

“…The estimated health impact of PCV was based on the observed vaccine impact in The Gambia. 8 The UNIVAC model framework (V.1.3.7) was then used to estimate the impact and cost-effectiveness of PCV at the national level under different vaccine pricing scenarios, and different assumptions about the underlying burden of disease. Model inputs included disease burden, healthcare utilisation and costs, as well as vaccine cost, coverage and the observed impact of PCV.…”

“…We used local data estimating case fatality for hospitalised cases of meningitis (33%) and sepsis (8.1%). 8 In the base case, we conservatively assumed the same case fatality rate for cases of meningitis or sepsis that did not seek treatment. Fifty-five percent of surviving meningitis cases resulted in neurological sequelae.…”

“…3 The age distribution of disease for non-severe pneumonia, severe pneumonia, meningitis and sepsis was defined based on hospital surveillance data linked to child age. 8 Burden of disease data were varied in alternative scenarios in accordance with CIs from the surveillance data. DALY weights for each disease outcome were taken from the 2016 Global Burden of Disease study and ranged from 0.051 for nonsevere pneumonia to 0.402 for meningitis sequelae.…”

“…The impact of PCV introduction was estimated from 10 years of population-based surveillance (from 2008 until 2017) in the Basse HDSS. 8 Programme impact was calculated dividing the incidence of disease in the final 2 years by the incidence in the first 2 years of surveillance. Using the final 2 years of surveillance, data mitigated potential concerns about transitory impact on disease.…”