October 2015 - Vaccination: from malaria to flu

Arnaud Marchant, Institute for Medical Immunology - IMI

Arnaud Marchant, this year the European Medicines Agency authorised the use of the RTS,S vaccine against malaria. Is this the end of a long struggle?

At any rate, it is a very important step. It is the first anti-malaria vaccine to be approved and its development by GSK Vaccines and its partners took around 30 years. Its efficacy however remains incomplete, because it only protects 36% of children and 28% of infants. Despite this partial efficacy, the World Health Organisation has decided to evaluate it in Africa on a very large scale by vaccinating one million children. Malaria kills around 300,000 children around the world each year, and preventing a third of these deaths would obviously constitute extremely significant progress. The authorisation to use this vaccine and its large scale evaluation are also very encouraging signals for research. We can hope that more effective vaccine candidates will be developed and tested in the coming years.

So the mood is optimistic?

We have witnessed a fair bit of success this year. GSK Vaccines has demonstrated the efficacy of a vaccine protecting the over-50s from shingles. Sanofi has also published the promising results of a vaccine against dengue fever. These successes indicate that we are probably witnessing the birth of a new era in vaccinology. Pathogens reputed to be complex and very difficult to control using traditional vaccinology approaches can today be controlled by vaccines developed thanks to a deeper knowledge of pathogens and their interactions with the immune system. Emerging pathogens also represent a significant challenge, with new vaccines having to be developed and tested over a very short period of time. In this respect, the demonstration by a large international consortium of the protective effects of a vaccine against the Ebola virus is very encouraging. All these results are very promising, but there still remains a lot of work to be done. We still do not have a vaccine against HIV and the vaccine which is available today against tuberculosis is only partially effective.

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Progress in vaccinology is also very promising in the field of cancer therapy. In a similar way to complex pathogens, tumoral cells escape immune defences. Understanding these escape mechanisms has led to the recent successes in cancer immunotherapy and is also encouraging the search for antitumor vaccines.

Here, vaccination seems to have eradicated a number of diseases to the extent that some people are wondering: is there any point in still vaccinating?

Yes, vaccination is still vital here, be it against measles, whooping cough or polio, for example. These pathogens are still in circulation around the world even if in our countries, thanks to vaccination, the diseases they cause occur less frequently or have disappeared. As we have been able to observe in recent years, a reduction in vaccination coverage brings about a resurgence of the disease and the development of epidemics. Demonstrating the safety of vaccines is very important in order to promote vaccination. This demonstration has been clearly made for vaccines that are currently administered. Considerable effort is made to ensure the safety of new vaccines. The results of these evaluations are essential for the decision to add new vaccines to the recommendations.

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Each autumn, we also see the reappearance of the flu vaccine. There again, is vaccination imperative? And effective?

The flu vaccine is effective and is particularly recommended for people at risk – in particular the elderly, patients suffering from chronic diseases, and pregnant women – or those in contact with these vulnerable people, especially health care staff. Seasonal flu can be caused by various types or sub-types of the influenza virus, which can change from one year to the next. This makes it difficult to produce a vaccine which is 100% effective. In order to improve the efficacy of vaccination, a vaccine covering four frequent sub-types, rather than three, has been made available this year. We are always making progress...