Pneumococcal conjugate vaccine induced IgG and nasopharyngeal carriage of pneumococci: Hyporesponsiveness and immune correlates of protection for carriage.

BACKGROUND: Prior studies have demonstrated hyporesponsiveness to pneumococcal conjugate vaccines (PCVs) when administered in the presence of homologous carriage. This may be substantially more important in Africa where carriage prevalence is high. Deriving a correlate of protection (CoP) for carriage is important in guiding the future use of extended PCVs as population control of pneumococcal disease by vaccination is now focused principally on its indirect effect. We therefore explored the complex relationship between existing carriage and vaccine responsiveness, and between serum IgG levels and risk of acquisition. METHODS: We undertook secondary analyses of data from two previously published clinical trials of the safety and immunogenicity of PCV in Kenya. We compared responses to vaccination between serotype-specific carriers and non-carriers at vaccination. We assessed the risk of carriage acquisition in relation to PCV-induced serum IgG levels using either a step- or continuous-risk function. RESULTS: For newborns, the immune response among carriers was 51-82% lower than that among non-carriers, depending on serotype. Among toddlers, for serotypes 6B, 14 and 19F the post-vaccination response among carriers was lower by between 29 and 70%. The estimated CoP against acquisition ranged from 0.26 to 1.93?g/mL across serotypes, however, these thresholds could not be distinguished statistically from a model with constant probability of carriage independent of assay value. CONCLUSION: We have confirmed hyporesponsiveness in an equatorial African setting in both infants and toddlers. Population responses to vaccination are likely to improve with time as carriage prevalence of vaccine serotypes is reduced. We have not found clear correlates of protection against carriage acquisition among toddlers in this population. Assessing the potential of new vaccines through the use of CoP against carriage is still difficult as there are no clear-cut serotype specific correlates

Providing “a beam of light to see the gaps”: determinants of implementation of the Systems Analysis and Improvement Approach applied to the pediatric and adolescent HIV cascade in Kenya

Abstract Background Children and adolescents living with HIV have poorer rates of HIV testing, treatment, and virologic suppression than adults. Strategies that use a systems approach to optimize these multiple, linked steps simultaneously are critical to close these gaps. Methods The Systems Analysis and Improvement Approach (SAIA) was adapted and piloted for the pediatric and adolescent HIV care and treatment cascade (SAIA-PEDS) at 6 facilities in Kenya. SAIA-PEDS includes three tools: continuous quality improvement (CQI), flow mapping, and pediatric cascade analysis (PedCAT). A predominately qualitative evaluation utilizing focus group discussions (N = 6) and in-depth interviews (N = 19) was conducted with healthcare workers after implementation to identify determinants of implementation. Data collection and analysis were grounded in the Consolidated Framework for Implementation Research (CFIR). Results Overall, the adapted SAIA-PEDS strategy was acceptable, and the three tools complemented one another and provided a relative advantage over existing processes. The flow mapping and CQI tools were compatible with existing workflows and resonated with team priorities and goals while providing a structure for group problem solving that transcended a single department’s focus. The PedCAT was overly complex, making it difficult to use. Leadership and hierarchy were complex determinants. All teams reported supportive leadership, with some describing in detail how their leadership was engaged and enthusiastic about the SAIA-PEDS process, by providing recognition, time, and resources. Hierarchy was similarly complex: in some facilities, leadership stifled rapid innovation by insisting on approving each change, while at other facilities, leadership had strong and supportive oversight of processes, checking on the progress frequently and empowering teams to test innovative ideas. Conclusion CQI and flow mapping were core components of SAIA-PEDS, with high acceptability and consistent use, but the PedCAT was too complex. Leadership and hierarchy had a nuanced role in implementation. Future SAIA-PEDS testing should address PedCAT complexity and further explore the modifiability of leadership engagement to maximize implementation