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Leveraging serology to titrate immunisation programme functionality for diphtheria in Madagascar.

ABSTRACT: Diphtheria is a potentially devastating disease whose epidemiology remains poorly described in many settings, including Madagascar. Diphtheria vaccination is delivered in combination with pertussis and tetanus antigens and coverage of this vaccine is often used as a core measure of health system functioning. However, coverage is challenging to estimate due to the difficulty in translating numbers of doses delivered into numbers of children effectively immunised. Serology provides an alternative lens onto immunisation, but is complicated by challenges in discriminating between natural and vaccine-derived seropositivity. Here, we leverage known features of the serological profile of diphtheria to bound expectations for vaccine coverage for diphtheria, and further refine these using serology for pertussis. We measured diphtheria antibody titres in 185 children aged 6-11 months and 362 children aged 8-15 years and analysed them with pertussis antibody titres previously measured for each individual. Levels of diphtheria seronegativity varied among age groups (18.9% of children aged 6-11 months old and 11.3% of children aged 8-15 years old were seronegative) and also among the districts. We also find surprisingly elevated levels of individuals seropositive to diphtheria but not pertussis in the 6-11 month old age group suggesting that vaccination coverage or efficacy of the pertussis component of the DTP vaccine remains low or that natural infection of diphtheria may be playing a significant role in seropositivity in Madagascar.

SUBMITTER: Razafimahatratra SL

PROVIDER: S-EPMC8888278 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Leveraging serology to titrate immunisation programme functionality for diphtheria in Madagascar.

Razafimahatratra Solohery L SL Menezes Arthur A Wesolowski Amy A Rafetrarivony Lala L Cauchemez Simon S Razafindratsimandresy Richter R Harimanana Aina A Crucitti Tania T Collard Jean Marc JM Metcalf C J E CJE

Epidemiology and infection 20220113

Diphtheria is a potentially devastating disease whose epidemiology remains poorly described in many settings, including Madagascar. Diphtheria vaccination is delivered in combination with pertussis and tetanus antigens and coverage of this vaccine is often used as a core measure of health system functioning. However, coverage is challenging to estimate due to the difficulty in translating numbers of doses delivered into numbers of children effectively immunised. Serology provides an alternative ...[more]

PMID: 35229710

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Project description:BackgroundPakistan has one of the highest infant and child mortality rates in the world, half of these occurring due to vaccine-preventable diseases. The country started its Expanded Programme on immunisation (EPI) in 1978. However, the programme's performance is often questioned, as the Immunisation rates have been chronically low and on-time vaccination unsatisfactory. We explored the programme's insights about its structural and implementation arrangements within the larger governance system, and the ensuing challenges as well as opportunities.MethodsWe carried out a qualitative case study comprised of semi-structured, in-depth interviews with 34 purposively selected key informants from various tiers of immunisation policy and programme implementation. The interviews revolved around WHO's six building blocks of a health system, their interactions with EPI counterparts, and with the outer ecological factors. Interviews were transcribed and content analysed for emergent themes.ResultsThe EPI faces several challenges in delivering routine immunisation (RI) to children, including lack of clarity on whether to provide vaccination through fixed centres or mobile teams, scarcity of human resource at various levels, lack of accurate population data, on-ground logistic issues, lack of a separate budget line for EPI, global pressure for polio, less priority to prevention by the policy, security risks for community-based activities, and community misconceptions about vaccines.ConclusionsThe fulcrum for most of the challenges lies where EPI service delivery interacts with components of the broader health system. The activities for polio eradication have had implications for RI. Socio-political issues from the national and global environment also impact this system. The interplay of these factors, while posing challenges to effective implementation of RI, also brings opportunities for improvement. Collective effort from local, national and global stakeholders is required for improving the immunisation status of Pakistani children, global health security and the sustainable development goals.

Project description:BackgroundImmunisation programmes have made substantial contributions to lowering the burden of disease in children, but there is a growing need to ensure that programmes are equity-oriented. We aimed to provide a detailed update about the state of between-country inequality and within-country economic-related inequality in the delivery of three doses of the combined diphtheria, tetanus toxoid, and pertussis-containing vaccine (DTP3), with a special focus on inequalities in high-priority countries.MethodsWe used data from the latest available Demographic and Health Surveys and Multiple Indicator Cluster Surveys done in 51 low-income and middle-income countries. Data for DTP3 coverage were disaggregated by wealth quintile, and inequality was calculated as difference and ratio measures based on coverage in richest (quintile 5) and poorest (quintile 1) household wealth quintiles. Excess change was calculated for 21 countries with data available at two timepoints spanning a 10 year period. Further analyses were done for six high-priority countries-ie, those with low national immunisation coverage and/or high absolute numbers of unvaccinated children. Significance was determined using 95% CIs.FindingsNational DTP3 immunisation coverage across the 51 study countries ranged from 32% in Central African Republic to 98% in Jordan. Within countries, the gap in DTP3 immunisation coverage suggested pro-rich inequality, with a difference of 20 percentage points or more between quintiles 1 and 5 for 20 of 51 countries. In Nigeria, Pakistan, Laos, Cameroon, and Central African Republic, the difference between quintiles 1 and 5 exceeded 40 percentage points. In 15 of 21 study countries, an increase over time in national coverage of DTP3 immunisation was realised alongside faster improvements in the poorest quintile than the richest. For example, in Burkina Faso, Cambodia, Gabon, Mali, and Nepal, the absolute increase in coverage was at least 2·0 percentage points per year, with faster improvement in the poorest quintile. Substantial economic-related inequality in DTP3 immunisation coverage was reported in five high-priority study countries (DR Congo, Ethiopia, Indonesia, Nigeria, and Pakistan), but not Uganda.InterpretationOverall, within-country inequalities in DTP3 immunisation persist, but seem to have narrowed over the past 10 years. Monitoring economic-related inequalities in immunisation coverage is warranted to reveal where gaps exist and inform appropriate approaches to reach disadvantaged populations.FundingNone.

Dataset Information

Leveraging serology to titrate immunisation programme functionality for diphtheria in Madagascar.

Publications

Leveraging serology to titrate immunisation programme functionality for diphtheria in Madagascar.

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