Vaccine Delivery Technologies
The need for thermostable vaccines
Vaccines are temperature sensitive and most of the currently available vaccines (such as those for measles, mumps, pertussis, tetanus, influenza) must be stored between 2ºC and 8ºC. Exposure to high or very low temperatures causes rapid loss of bioactivity. Maintaining the cold chain (refrigerating vaccines at every step of the transportation and storage process) increases the cost of immunisation by 14% (source: WHO), but most importantly vaccine damage as a result of cold chain breakages costs human lives.
This challenge is particularly acute in mass vaccination programmes in developing countries where high ambient temperatures and lack of infrastructure to support a reliable cold-chain leads to vaccine wastage rates of 25-50%. As recently as 2007, 151 million vaccine doses were wasted (source: Gates Grand Challenges).
Thermal stabilisation of vaccines has been identified as one of the much-needed technologies capable of transforming immunization programmes in the 21st century and is seen as a strategic priority for the WHO, GAVI, PATH and Bill and Melinda Gates Foundation.
Sugar preserves vaccines without refrigeration
A simple and cheap way of making vaccines stable – even at tropical temperatures – has been developed by the scientists at the Jenner Institute and Cambridge Biostability Ltd. The technology involves mixing the vaccine with the sugars trehalose and sucrose. The mixture is then left to slowly dry out on a simple filter or membrane. As it dries and the water evaporates the vaccine mixture turns into a syrup and then fully solidifies as a glass on the membrane. The thin sugar-glass that forms on the membrane preserves the active part of the vaccine in ‘suspended animation’, protected from degradation even at high temperature. Flushing the membrane with water instantly rehydrates the vaccine from the membrane.
The research article can be found here.
Harnessing this thermostabilising technology for field-usable vaccines is the next goal of the work programme at the Jenner Institute. The World Health Organisation’s immunisation programme vaccinates nearly 80% of the children born today against six killer diseases: polio, diphtheria, tuberculosis, whooping cough, measles and tetanus.
One of the biggest costs is the cold chain – making sure vaccines are refrigerated all the way from the manufacturer to the child, whether they are in the Western world or in the remotest villages in Africa. If most or all of these vaccines could be stabilised at high temperatures, it would both reduce cost, and more children would be vaccinated, saving many lives.
Stabilising a vaccine for NDV, a fatal disease of poultry
Newcastle disease (ND) is a highly contagious disease affecting a number of avian species causing very high mortality, sometimes approaching 100 per cent. The global economic impact of virulent Newcastle disease is enormous, particularly for many developing countries in Africa, where death from the disease causes hundreds of millions of deaths per annum in poultry. Although ND vaccines can offer protection, they are unstable and need an intact ‘cold chain’ during transport and storage, which is often not available to farmers in low-resource countries, particularly in remote settings. An additional problem is that current vaccines are available as 500-1000 dose vials; these large multi-dose formulations make them impractical for smaller poultry units.
In 2015 the Jenner Institute (Professors Adrian Hill at Oxford and Venugopal Nair at Pirbright) was awarded funding from BBSRC to produce a thermo-stable form of the ND vaccine using sugar-membrane technology, which will not require refrigeration. The project aims to produce membrane sheets impregnated with sugar-formulated ND vaccine which can be cut into different sizes according to the size of the flocks requiring vaccination.
We welcome opportunities for collaboration or business partnership. Enquiries can be directed to Dr Rebecca Ashfield:
Tel: +44 (0)1865 617627
Adrian Hill, Programme Leader
Rebecca Ashfield, Senior Project Manager
Pawan Dulal, Research Assistant & DPhil Student