London: For the first time scientists at
Oxford University have found a way of keeping vaccines stable
without refrigeration, even at tropical temperatures.
The technology has the potential to revolutionise
vaccination efforts, particularly in the developing world
where infectious diseases kill millions of people every year,
by removing the need for fridges, freezers and associated
health infrastructure.
The work published in the journal Science Translational
Medicine involved collaboration between the university
scientists and a company, Nova Bio-Pharma Technologies.
Scientists carried out the proof-of-concept study,
showing that vaccines they are developing could be stabilised
for months using Nova`s patented technology, called the
Hypodermic Rehydration Injection System (HydRIS).
"Currently vaccines need to be stored in a fridge or
freezer," explains lead author Dr Matt Cottingham of the
Jenner Institute at the University of Oxford.
"That means you need a clinic with a nurse, a fridge and
an electricity supply, and refrigeration lorries for
distribution".
He added: "If you could ship vaccines at normal
temperatures, you would greatly reduce cost and hugely improve
access to vaccines. You could even picture someone with a
backpack taking vaccine doses on a bike into remote
villages.”
The team demonstrated it was possible to store two
different virus-based vaccines on sugar-stabilized membranes
for 46 months at 45 degree Celsius without any degradation.
The vaccines could be kept for a year and more at 37 degree Celcius
with only tiny losses in the amount of viral vaccine
re-obtained from the membrane.
"We`ve shown that a very simple way of heat-stabilizing
vaccines works for two viruses that are being used as the
basis for novel vaccines in development," says principal
investigator Professor Adrian Hill of Oxford University.
"This is so exciting scientifically because these viruses
are fragile. If we are able to stabilize these, other vaccines
are likely to be easier," he said.
The method 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 on the membrane.
The thin sugary film that forms on the membrane preserves
the active part of the vaccine in a kind of suspended
animation, protected from degradation even at high
temperature.
Flushing the membrane with water rehydrates the vaccine
from the membrane in an instant.
"The beauty of this approach is that a simple plastic
cartridge, containing the membrane with vaccine dried on, can
be placed on the end of a syringe," explains Dr Cottingham.
Pushing a liquid solution from the syringe over the
membrane would then release the vaccine and inject it into the
patient.
Professor Hill adds: "The World Health Organization’s
immunization programme vaccinates nearly 80 per cent of the
children born today against six killer diseases: polio,
diphtheria, tuberculosis, whooping cough, measles and tetanus.
"One of the biggest costs is maintaining what`s called
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 the remotest village in Africa," he said.
If most or all of the vaccines could be stabilized at
high temperatures, it would not only remove cost, more
children would be vaccinated, he said.
PTI
