Impact of Vaccines on Antimicrobial Microbial Resistance

Type of research study: A series of community and health centre based cross-sectional surveys

Problem: Pneumonia is a leading cause of child mortality globally and Streptococcus pneumoniae a leading cause of lower respiratory tract infections (LRTI) in under-fives. Malaria remains endemic in much of sub- Saharan Africa, commonly causing febrile illness in children and despite substantial progress with control programmes, Malaria continues to be a leading cause of child mortality. Vaccination is therefore an attractive solution.

Vaccines are thought to be crucial to Anti-Microbial Resistance (AMR) control but their impact on AMR may be more complex than originally thought. Both the direct and indirect impacts of vaccine on AMR require a systematic evaluation. In collaboration with the Malawi Ministry of Health, we are commencing two funded, regulatory approved, cluster-randomised evaluations of vaccines that target two of the commonest causes of febrile illness and life-threatening disease in children under 5 years in Africa: pneumococcal invasive infection, and malaria. This study will leverage two large funded cluster- randomised vaccine evaluations (13-valent Pneumococcal Conjugate Vaccine (PCV13) schedule change of 3+0 to 2+1 and RTS,S/AS01 (trade name Mosquirix) malaria vaccine introduction). We will assess the selective effects of pneumococcal and malaria vaccines on antibiotic resistance, febrile illness and antibiotic usage in children <3 years.

Hypothesis: Extending vaccine-mediated protection against Streptococcus pneumoniae through a 3+0 to 2+1 schedule change will be associated with a reduction in the prevalence of S. pneumoniae carriage isolates with increased AMR in children <3 years. The introduction of the malaria vaccine will reduce the frequency of healthcare attendances resulting in antibiotic prescription, reduce the prevalence of Extended spectrum beta-lactamases (ESBL) Escheriquia coli or Klebsiellae in the stool of children <3 years, and change the upper respiratory tract resistome profile in children <3years.

Aim: To establish the direct and indirect selective effects of pneumococcal and malaria vaccines on antibiotic resistance, febrile illness, and antibiotic usage in young children in Malawi.

Objectives:

1. To establish the antibiotic resistance profile of S. pneumoniae carriage isolates from children <3 years following a PCV13 schedule change that extends protection (2+1 vs. 3+0), or the introduction of malaria vaccine (RTS,S/AS01)
2. To assess the frequency of febrile illness and antibiotic use in children <3 years after PCV13 schedule change or malaria vaccine introduction
3. To investigate change in the upper respiratory tract resistome in children <3 years after PCV13 schedule change or malaria vaccine introduction.

Methodology: Three cross sectional sampling surveys shall be conducted (1) shortly following introduction of PCV13 2+1, followed by surveys 18 and 33 months after introduction, and (2) for RTS,S/AS01 2.5 years, 3 years and 3.5 years after introduction, in clusters defined through two large cluster-randomised vaccine evaluation studies. These will include the collection of nasopharyngeal and rectal swabs, and the completion of an Individual questionnaire on febrile illness episodes, malaria Rapid Diagnostic Test (RDT) use, and medicine usage with a focus on antibiotics. Additionally, we will monitor antimicrobial prescription and febrile illness at health centre level within the communities where the study will take place by conducting Health Centre (HC) Audits. These will consist of very brief anonymized "exit interviews" to randomly selected Outer-Patient Department (OPD) users, in which we will record information on the relevant vaccine (either RTS,S/AS01 or PCV13), malaria RDT (as a proxy for febrile illness) and medicine prescription

Expected Results Nasopharyngeal and rectal swabs obtained from participants will be tested for the presence of S. pneumoniae, and E. coli and Klebsiella isolates respectively. Bacterial isolates will be tested for the presence of AMR genes, and resistance profiles will be analysed in relation to their association to either the introduction of the RTS,S/AS01 vaccine or the PCV13 schedule change, and in the context of antibiotic prescription and usage for febrile illness episodes.

Outcome Measures:

Primary: The antibiotic resistance profile of S. pneumoniae carriage isolates from children <3 years following a PCV13 schedule that extends protection (2+1 vs. 3+0) or the introduction of malaria vaccine (RTS,S/AS01)

Secondary:

1. The frequency of febrile illness and antibiotic use in children <3 years after PCV13 schedule changeor malaria vaccine introduction.
2. The stool carriage of ESBL E. coli or Klebsiella in children <3 years after PCV13 schedule change or malaria vaccine introduction.
3. The change in the upper respiratory tract resistome in children <3 years after PCV13 schedule change or malaria vaccine introduction.

Population Eligibility: For the PCV13 schedule change, each cross-sectional survey shall recruit children between the ages of 4-9 months for the baseline survey, and 15 and 24 months old for the subsequent surveys, resident in Blantyre district, recruited from the community. For RTS,S/AS01, each cross-sectional survey shall recruit children between the ages of 18 and 36 months, resident in Mangochi, recruited from the community. Anonymous audits of RDT and medicine use in children <3 years attending a subset of HCs for investigation of ill health will also be conducted.

Findings' dissemination: Investigators will seek timely publication in peer-reviewed journals. Partial results and interim analyses will be shared with the Malawi Ministry of Health (MoH), and other relevant policymakers and decision-making stakeholders. Partial and final findings will be presented at the College of Medicine (COM Research Dissemination Day, Malawi-Liverpool Wellcome Trust (MWL) research in progress meetings and international scientific conferences. A copy of all published materials and reports will be shared with College of Medicine Research Ethics Committee (COMREC), and the Malawi College of Medicine Library.