Fascinating evidence published this week has indicated that one day silk, the common material used for clothing, could help us reach more people with life-saving vaccines. This is because the study indicates proteins found in silk could remove the need for vaccines to be kept at low temperatures and therefore transported through cold chains.
So what is the cold chain? As vaccines are biological products, they must be kept within a narrow temperature range, usually 2-8 degrees Centigrade (36-45º F). The cold chain refers to the storage and transport equipment that keeps vaccines refrigerated from the point of manufacture to the point of use where a person is immunised.
Many health products have attributes that make their use difficult in places with weak health systems and insufficient cold chain capacity. For cold chains to function properly, they require reliable and adequate electricity supply, fridges in working order and production of ice packs to be used during transportation. This appears harder still when one appreciates the hot climates of numerous developing countries.
The study suggested that proteins found in silk could help protect some vaccines and drugs from heat damage, eliminating the need for vaccine refrigeration. As National Public Radio in the US described:
“Chemicals in vaccines and some antibiotics given by injection must stay in the right folded shape to work properly. When exposed to heat or moisture those folds can unfold, and the drugs or vaccines can no longer challenge the bacteria or viruses they were designed to battle”, says Dr. David Kaplan, a bioengineering professor at Tufts University and lead author on the study.
Silk proteins stabilize the medicines and act to “pin the structure in place,” Kaplan says.
With the addition of these silk supports, the vaccine (against measles, mumps and rubella) and two antibiotics were able to retain their potency at temperatures over 100 degrees for two weeks or more. Without silk stabilizers, heat that high saps their effectiveness in less than a day.”
Can new ways of delivering vaccines help us reach the final fifth?
This research was in fact intended to help lower costs in clinics in the US incurred by refrigeration facilities, but as a very welcome by-product, this discovery could have a global impact.
A report published earlier this year by Save the Children and ACTION, ‘Finding the Final Fifth – Inequities in Immunisation’, stressed remote rural populations are less likely to have access to basic health services. This can be due to various factors, such as needing to travel long distances to reach health centres or a lack of properly trained health workers. But even if such factors are overcome, the availability of the vaccine is crucial. Vaccines and related products need to reach all districts, all facilities, and be appropriately stored and ready for use. This depends on an adequate cold chain.
A recent report from Médecins Sans Frontières MSF (Doctors Without Borders) The Right Shot: Extending the Reach of Affordable and Adapted Vaccines, highlighted these challenges in great depth, while pointing towards ways in which they can be overcome. This included through developing new products, adapted to country settings, that do not require effective cold chains to be in place. Such alternative technologies alternatives include micro-needles, inhalation, or oral administration.
If the global health community is able to circumnavigate the lack of cold chain capacity, we may have a better chance of reaching the final fifth of unimmunised children.