A new method that stops vaccines from degrading in warm temperatures could help children in low-income nations receive life-saving inoculations, scientists have said.
The researchers from the universities of Bath and Newcastle believe they have found a way to make transportation and storage of vaccines safer without the need for refrigeration.
Their new method, known as ensilication, involves encasing the protein molecules in a vaccine in a non-toxic silica shell.
Study author Dr Asel Sartbaeva, from the University of Bath, said their process “preserves not just the structure of the vaccine proteins but also the function”, allowing the biological substance to work without temperature constraints.
At present, all vaccines follow a cold chain procedure which requires refrigeration at all times, from the manufacturing stage to the point of administration. This temperature-controlled supply chain ensures vaccines are always stored between 2°C and 8°C.
However, despite best efforts, around 50 per cent of vaccine doses are discarded before use due to logistical issues associated with temperature control, according to estimates from the World Health Organisation.
At higher temperatures, the proteins in vaccines can start to unravel making them ineffective. Encasing these protein molecules in a silica shell enables their structure to remain intact – allowing the vaccines to be stored at room temperature for up to three years, the researchers said.
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Dr Sartbaeva said: “We build our shell in a way so that it is completely encases the protein and stops the protein from unfolding – because it is this physical unfolding which leads to the breaking of the proteins inside the vaccines and it leads to the denaturation or spoiling of these vaccines.”
The researchers tested ensilicated and regular samples of the tetanus vaccine on mice and found the silica-coated vaccines triggered an immune response, while the regular samples did not.
The team plans to work on developing thermally-stable vaccines for diseases such as diphtheria and whooping cough.
Dr Sartbaeva said: “Ultimately, we want to make important medicines stable so they can be more widely available. The aim is to eradicate vaccine-preventable diseases in low income countries by using thermally stable vaccines and cutting out dependence on cold chain.”
The findings are published in the journal Scientific Reports.
How do scientists develop vaccines for new viruses?
Vaccines work by fooling our bodies into thinking that we’ve been infected by a virus. Our body mounts an immune response, and builds a memory of that virus which will enable us to fight it in the future.
Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been ‘killed’, but which still activate the immune system), and attenuated vaccines (which use live viruses that have been modified so that they trigger an immune response without causing us harm).
A more recent development is recombinant vaccines, which involve genetically engineering a less harmful virus so that it includes a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.
Over the past few years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against the Ebola virus. It consists of a vesicular stomatitis animal virus (which causes flu-like symptoms in humans), engineered to have an outer protein of the Zaire strain of Ebola.
Vaccines go through a huge amount of testing to check that they are safe and effective, whether there are any side effects, and what dosage levels are suitable. It usually takes years before a vaccine is commercially available.
Sometimes this is too long, and the new Ebola vaccine is being administered under ‘compassionate use’ terms: it has yet to complete all its formal testing and paperwork, but has been shown to be safe and effective. Something similar may be possible if one of the many groups around the world working on a vaccine for the new strain of coronavirus (SARS-CoV-2) is successful.
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