38 – Preventing malaria: how might malaria vaccines complement other interventions?

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This panel discussed the current knowledge regarding malaria vaccines. Prospects and challenges ahead for future introduction in malaria endemic areas were discussed, and a brief summary on the malaria vaccine development pipeline also presented.

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Copyright UNICEF/2010/Alexandra Rosetti

This panel discussed the current knowledge regarding malaria vaccines, with particular emphasis on the most advanced to date malaria vaccine candidate, GSK’s RTS,S. Prospects and challenges ahead for future introduction in malaria endemic areas were discussed, and a brief summary on the malaria vaccine development pipeline also presented.

The moderator, Dr. Pedro Alonso, Director, from the Barcelona Institute for Global Health, introduced the session by noting that it was the first time that there was a malaria session at the GAVI Partners Forum discussing the perspective of a vaccine.

He reminded the importance of malaria and its evolution.

While transmission was occurring in most countries in the world in 1900, we are moving towards elimination in many parts of the world.

The African continent is concentrating the largest burden of disease, with 81% of the cases. Amongst the 655,000 deaths in 2011, 91% occurred in Africa, 86% in children under 5. Substantial progress has been made since 2004, thanks to an unprecedented financial effort, which allowed the distribution of 254 million of ITNs (insecticide treated nets), the protection of 75 million people by IRS (indoor residual spraying) and the distribution of 158 million treatments ACT (artemisinin based combination therapy).

But the fight is never over, and the challenge is to keep up: Zanzibar is eliminating malaria for the 3rd time in history.

Dr. Salim Abdulla, Chief Executive Director, Ifakara Health Institute (IHI), Tanzania, presented an historical background of RTS,S development. The vaccine candidate has more than 27 years of development, illustrating the major difficulty in developing what would be the first vaccine against a parasitic disease. It has involved extensive collaboration between universities, research centres, industry (GSK), and numerous stakeholders.

The first trials were conducted in 1998 in Ghana. A study (key proof of concept) in children was conducted in Mozambique in 2004. The phase 3 is conducted in 11 centres from 7 countries, measuring the vaccine efficacy against clinical malaria during 12 months follow up in two age groups (5-17 months and 6-12 weeks).

The results for the first age group (5-17 months) did show a 55.8% efficacy against clinical malaria, and 47.3% against severe malaria.

In the second age group, efficacy was respectively 31.3% and 36.6%. It is the first time that a vaccine is efficacious, and its benefits are over and beyond the use of ITN.

The challenge is now to confirm efficacy, to better understand the interplay between intensity of exposure, immune response and vaccine efficacy. The duration of immunity and the question of booster will require additional studies.

The panel debated whether this intervention is cost-effective, and whether it would replace other interventions. It was made clear that vaccine would be used alongside (and not replace) other malaria control interventions. Additional data is needed to understand how the vaccines works in different contexts to help the decision making in terms of cost-effectiveness and value added.

Dr. David Kaslow, Global Program Le ader of the Malaria Vaccine Initiative, USA, presented an update of the R&D pipeline of malaria vaccine. 27 vaccines are in early development stage, and 4 in late development, with 3 priority programs (2 in phase 2b and RTS,S in phase 3 clinical trials). All candidates are targeted at Plasmodium Falciparum, none at Plasmodium Vivax.

Dr. Vasee Moorthy, from WHO, discussed the potential role of a malaria vaccine in the context of existing malaria control measures. The RTS,S/AS01 vaccine policy recommendations from WHO are expected in 2015. Policy decision depends on WHO evidence-based assessment, and critical data will not be available before 2014. In addition, policy recommendations cannot occur without a positive regulatory review by a stringent regulatory authority

Data available in 2015-2016 will allow assessment of RTS,S only for efficacy against morbidity. Further data on administration to wider age groups will be necessary before consideration for any possible contributory role in elimination in some settings

Dr Awa Coll Seck, Minister of Health, Senegal, identified the many challenges that have to be addressed.

The first is the validation by the international community, including WHO recommendation after expert evaluation, but also GAVI’s commitment and support.

The second is financing, both at international and national levels, which has to be discussed early, in order not to delay the introduction of the vaccine.

The third is at community level, and will require a strategic approach to communication and education, as this vaccine will not completely protect against malaria, and will have to be combined with other preventive measures.

The fourth relates to country policy: will the vaccine be integrated in EPI? What will be the target age group? What should be the geographical targeting in countries with different epidemiological settings? When, in case of seasonal transmission?

The last challenge is monitoring and evaluation.

The biggest challenge will be to manage expectations, explain that cases of disease do not necessarily mean failure of the vaccines. Questions will come from communities as well as from decision makers. It will be critical in this context to harmonize messages, and a platform with Q&A should be launched.

The conclusions from the session were that:

  - The vaccine will be an addition to the available interventions, not an end

  - Public health impact has to be weighed against efficacy: major public health gains can be made without 100% efficacy

  - This vaccine will represent “new ground” for the vaccine community, and its deployment will have to be thoroughly prepared and discussed with countries and programs.

41 million

Since 2007, countries have immunised 41 million children with a second dose of measles or measles-rubella vaccine with Gavi support. Gavi-funded campaigns with these two vaccines have helped vaccinate another 328 million children in countries at high risk of outbreaks.

WHO/UNICEF and Gavi, 2017

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