Measures to increase access to a lifesaving childhood vaccine have been recommended by the World Health Organization (WHO) following extensive research from the app of Hygiene & Tropical Medicine (LSHTM) and partners.
Pneumococcal conjugate vaccines protect children from the dangerous Streptococcus pneumoniae bacterium, which can lead to severe illnesses including pneumonia, septicaemia, and meningitis.
The vaccines have saved more than 1.6m lives since they were introduced in 2000. However, the relatively high cost of PCV poses a barrier for sustainable access in many countries The WHO has now expanded their recommendations on PCV use, to allow countries with high vaccine coverage and sufficient surveillance capacity to either give two instead of the usual three doses or by fractionating doses of one of the products. The expansion of the recommendation also included addressing immunity gaps through multi age cohort vaccination campaigns, for example in humanitarian crises.
The updated policy is based on evidence from major trials and research around the world by LSHTM and partners. The from the WHO Strategic Advisory Group of apps on Immunisation (SAGE), following input from the .
Researchers from LSHTM have been involved in many clinical trials and modelling studies focused on pneumococcal conjugate vaccines. Teams based in The Gambia established their safety and effectiveness in the early 2000s, which led to the life-saving vaccines being introduced worldwide. This was followed by further studies into community impact carried out with successive vaccines in The Gambia and Kenya.
More recently, attention has focused on investigating approaches to help increase coverage, reduce costs and thus save more lives around the world. This has included clinical trials with partners in The Gambia (the Pneumococcal Vaccine Schedules – PVS – study at MRCG) and Vietnam on the impact of reducing the number of doses; evaluating fractional doses in Kenya and Niger; and in Somaliland to study vaccine interventions in humanitarian crises.
Findings from the Vietnam study showed that reducing the number of PCV vaccine doses from three to two could achieve similar rates of pneumococcal transmission in communities, thus maintaining the herd immunity of PCV programmes. The PVS study at the MRC Unit The Gambia found the two-dose schedule to be as safe and effective as the standard three-dose schedule to control pneumococcal disease. Results from Kenya found that fractional doses of one of the vaccines (PCV13) led to similar, non-inferior immune responses compared to the full dose.
Grant Mackenzie, Professor at LSHTM, said: “The PVS study is a collaborative effort between MRCG at LSHTM and the Gambian Ministry of Health. PVS enrolled 33,001 infants with surveillance over 4 years, showing that the two-dose PCV schedule was safe and just as effective as the three-dose schedule to prevent pneumococcal disease. The revised WHO recommendation indicates that the reduced dose schedule can be considered for adoption in many settings.”
Kevin van Zandvoort, Research Fellow at LSHTM, said: “Mathematical modelling evidence suggests that, even in higher transmission settings, a two-dose PCV schedule will sustain most of the population-level impact of a three-dose schedule. Reduced dose schedules could help keep PCV programmes affordable.
“PCVs remain underutilized in crisis-affected settings. Our studies -a collaboration between LSHTM, Save the Children, the Somaliland Ministry of Health Development, and the Murdoch Children’s Research Institute- showed that a single-dose PCV campaign vaccinating children up to, at least, 4 years of age, can effectively protect populations affected by humanitarian crises from pneumococcal disease. Single-dose PCV campaigns can be used as an effective and pragmatic tool to protect these hard-to-reach populations.”
Kate Gallagher, Associate Professor at LSHTM, said: “The fractional dose Pneumococcal Conjugate Vaccine Trial was designed together with representatives from the Kenyan Ministry of Health and the National immunisation technical advisory group to explore one option to reduce the cost of sustaining the PCV programme when Kenya transitions away from Gavi support.
The trial found that a 3-dose schedule using 40%doses of the 13-valent vaccine generated non-inferior immunogenicity and no difference in carriage, compared to a full dose schedule. The WHO has indicated that 40% doses of the 13-valent vaccine could be considered in settings with funding constraints and where real-world data can be collected to monitor the impact over time.”
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