Evaluation of a phased pneumococcal conjugate vaccine introduction in Mongolia using enhanced pneumonia surveillance and community carriage surveys: a study protocol for a prospective observational study and lessons learned.

BACKGROUND: Streptococcus pneumoniae causes substantial morbidity and mortality among children. The introduction of pneumococcal conjugate vaccines (PCV) has the potential to dramatically reduce disease burden. As with any vaccine, it is important to evaluate PCV impact, to help guide decision-making and resource-allocation. Measuring PCV impact can be complex, particularly to measure impact on one of the most common and significant diseases caused by the pneumococcus, namely pneumonia. Here we outline the protocol developed to evaluate the impact of 13-valent PCV (PCV13) on childhood pneumonia in Mongolia, and a number of lessons learned in implementing the evaluation that may be helpful to other countries seeking to undertake pneumonia surveillance. METHODS: From 2016 PCV13 was introduced in a phased manner into the routine immunisation programme with some catch-up by the Government of Mongolia. We designed an evaluation to measure vaccine impact in children aged 2-59 months with hospitalised radiological pneumonia as a primary outcome, with secondary objectives to measure impact on clinically-defined pneumonia, nasopharyngeal carriage of S. pneumoniae among pneumonia patients and in the community, and severe respiratory infection associated with RSV and/or influenza. We enhanced an existing hospital-based pneumonia surveillance system by incorporating additional study components (nasopharyngeal swabbing using standard methods, C-reactive protein, risk factor assessment) and strengthening clinical practices, such as radiology as well as monitoring and training. We conducted cross-sectional community carriage surveys to provide data on impact on carriage among healthy children. DISCUSSION: Establishing a robust surveillance system is an important component of monitoring the impact of PCV within a country. The enhanced surveillance system in Mongolia will facilitate assessment of PCV13 impact on pneumonia, with radiological confirmed disease as the primary outcome. Key lessons arising from this evaluation have included the importance of establishing a core group of in-country staff to be responsible for surveillance activities and to work closely with this team; to be aware of external factors that could potentially influence disease burden estimates; to be flexible in data collection processes to respond to changing circumstances and lastly to ensure a consistent application of the pneumonia surveillance case definition throughout the study period.

An opportunity missed: Strengthening health system data on multisystem inflammatory syndrome in children from low- and middle-income countries in Asia.

Background: Multisystem inflammatory syndrome in children (MIS-C) is a severe complication associated with SARS-CoV-2 infection. The clinical epidemiology of MIS-C is not completely understood in low- and middle-income countries (LMICs) due to limited reporting, including in Asia where there was a substantial burden of COVID-19. We aimed to discuss the challenges of diagnosing MIS-C and factors which may cause children from Asian LMICs to have an increased risk of MIS-C. Methods: Not applicable. Results: The burden of MIS-C in Asian LMICs may be disproportionately high due to underlying risk factors, resource-limited health systems, and the increased infectivity and transmissibility of recent SARS-CoV-2 variants. Complex clinical features of MIS-C contributed to missed or delayed diagnosis and treatment, while underlying risk factors including ethnicity, chronic health conditions, and socioeconomic factors may have predisposed children in Asian LMICs to MIS-C. Conclusions: There was a lack of data on the clinical epidemiology of MIS-C in Asian LMICs during the COVID-19 pandemic, despite reports of higher paediatric mortality rates compared to high-income countries. This highlights the need for LMICs to have strong surveillance systems to collect high-quality and timely data on newly emerging complications associated with a pandemic, such as MIS-C. This will lead to rapid understanding of these emerging complications, and inform clinical management, disease prevention and health system planning.