Four years of case-based surveillance of meningitis following the introduction of MenAfriVac in Moissala, Chad: lessons learned.

OBJECTIVE: Case-based surveillance of bacterial meningitis in sentinel districts has been recommended after the introduction of the conjugated vaccine against Neisseria meningitidis serogroup A (NmA), MenAfriVac, in the African meningitis belt. Here we report data and lessons learnt from four years of surveillance in the district of Moissala, Chad. METHODS: All suspected cases of meningitis were referred free of charge to the district hospital for lumbar puncture and treatment. Cerebrospinal fluid samples were tested with Pastorex latex agglutination in Moissala, and inoculated trans-isolate media were used for culture and PCR at the national reference laboratory and/or at the Norwegian Institute of Public Health. RESULTS: From July 2012 to December 2016, 237 suspected cases of meningitis were notified, and a specimen was collected from 224. Eighty-three samples were positive for a bacterial pathogen by culture, PCR or Pastorex, including 58 cases due to Streptococcus pneumoniae with only 28 of 49 pneumococcal meningitis confirmed by culture or PCR correctly identified by Pastorex. Four cases of NmA were detected by Pastorex, but none were confirmed by PCR. CONCLUSION: Implementation of case-based surveillance for meningitis is feasible in Chad, but has required political and technical engagement. Given the high proportion of S. pneumoniae and its poor detection by Pastorex, continued use of PCR is warranted for surveillance outside of outbreaks, and efforts to accelerate the introduction of pneumococcal conjugate vaccines are needed. Introduction of MenAfriVac in routine immunisation and future availability of a pentavalent meningococcal conjugate vaccine will be key elements for the sustained reduction in meningitis outbreaks in the area.

Can vaccination coverage be improved by reducing missed opportunities for vaccination? Findings from assessments in Chad and Malawi using the new WHO methodology.

BACKGROUND: In 2015, the World Health Organization (WHO) updated the global methodology for assessing and reducing missed opportunities for vaccination (MOV), when eligible children have contact with the health system but are not vaccinated. This paper presents the results of two pilot assessments conducted in Chad and Malawi. METHODS: Using the ten-step global WHO MOV strategy, we purposively selected districts and health facilities, with non-probabilistic sampling of <24 month old children for exit interviews of caregivers and self-administered knowledge, attitudes, and practices (KAP) surveys of health workers. MOV were calculated based on a child's documented vaccination history (i.e., from a home-based record (HBR) or a health facility vaccination register), including selected vaccines in the national schedule. RESULTS: Respondents included caregivers of 353 children in Chad and of 580 children in Malawi. Among those with documented vaccination history, 82% (195/238) were eligible for vaccination in Chad and 47% (225/483) in Malawi. Among eligible children, 51% (99/195) in Chad, and 66% (149/225) in Malawi had one or more MOV on the survey date. During non-vaccination visits, 77% (24/31) of children eligible for vaccination in Chad and 92% (119/129) in Malawi had a MOV compared to 46% (75/164) and 31% (30/96) during vaccination visits, respectively. Among health workers, 92% in Chad and 88% in Malawi were unable to correctly identify valid contraindications for vaccination. CONCLUSION: The new MOV tool was able to characterize the type and potential causes of MOV. In both countries, the findings of the assessments point to two major barriers to full vaccination of eligible children-a lack of coordination between vaccination and curative health services and incomplete vaccination during vaccination visits. National immunization programs should explore tailored efforts to improve health worker practices and to increase vaccine delivery by making better use of existing health service contacts.

A cluster randomized non-inferiority field trial on the immunogenicity and safety of tetanus toxoid vaccine kept in controlled temperature chain compared to cold chain.

BACKGROUND: In resource-poor settings, cold chain requirements present barriers for vaccine delivery. We evaluated the immunogenicity and safety of tetanus toxoid (TT) vaccine in "Controlled Temperature Chain" (CTC; up to 40 °C for <30 days before administration), compared to standard cold chain (SCC; 2-8 °C). Prior to the study, stability parameters of TT-CTC were shown to meet international requirements. METHODS: A cluster randomized, non-inferiority trial was conducted in Moïssala district, Chad, December 2012-March 2013. Thirty-four included clusters were randomized to CTC or SCC. Women aged 14-49 years, eligible for TT vaccination and with a history of ≤1 TT dose, received two TT doses 4 weeks apart. Participants were blinded to allocation strategy. Tetanus antibody titers were measured using standard ELISA at inclusion and 4 weeks post-TT2. Primary outcome measures were post-vaccination seroconversion and fold-increase in geometric mean concentrations (GMC). Non-inferiority was by seroconversion difference (TTSCC-TTCTC) <5% and ratio of GMCs (TTSCC/TTCTC) <1.5. Adverse events were monitored at health centers and at next contact with participants. RESULTS: A total of 2128 women (CTC=1068; SCC=1060) were recruited. Primary intention to vaccinate analysis included 1830 participants; 272 of these were included in the seroconversion analysis. Seroconversion was reached by >95% of participants; upper 95%CI of the difference was 5.6%. Increases in GMC were over 4-fold; upper 95%CI of GMC ratio was 1.36 in the adjusted analysis. Few adverse events were recorded. CONCLUSIONS: This study demonstrates the immunogenicity and safety of TT in CTC at <40 °C for <30 days. The high proportion of participants protected at baseline results in a reduction of power to detect a 5% non-inferiority margin. However, results at a 10% non-inferiority margin, the comparable GMC increases and vaccine's stability demonstrated in the preliminary phase indicate that CTC can be an alternative strategy for TT delivery in situations where cold chain cannot be maintained.