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Future vaccines may be administered using only a patch and may not have stringent storage temperature requirements. Future vaccines may be administered using only a patch and may not have stringent storage temperature requirements. Image: Christine Daniloff/MIT

Vaccine Developments look to cut out Syringe, Cold Chain

One of the greatest challenges in expanding HIV, tuberculosis and other vaccination campaigns is delivering the temperature sensitive vaccines to remote and resource-limited health facilities.  Because vaccines must be between 2° and 8° C at all times, they are highly dependent on the cold-chain, which in turn depends on energy resources such as grid power or diesel fuel – often unreliable and expensive for such facilities.

Two recent, but early developments in vaccination technology hold potential for eliminating vaccine’s dependence on the cold chain as well as the syringe.  These parallel advances utilize microneedles, arrays of micron-scale needles coated to a patch, which when applied to the skin delivers a vaccine.

The first comes from researchers at MIT, who have demonstrated the effectiveness of delivering a DNA-based vaccine using microneedles.  Unlike normal live-virus vaccines, DNA vaccines are potentially safer for aggressive viruses like HIV.  The researchers formulated a DNA-vaccine in thin layers of polymer film which are embedded in the skin using a microneedle patch.  Once there, the polymers hold the DNA in place for days or weeks, triggering an effective immune response.

The second development is from Kings College London, where researchers have encapsulated a dried live-virus vaccine into an array of sugar microneedles.  Similar to the MIT approach, these microneedles are embedded into the skin, but in this case the sugar is quickly dissolved, and the vaccine is released over a shorter period.  The effectiveness of this method was found to be equivalent to a conventional, liquid vaccine stored at -80°C.

These approaches have many potential advantages.  Because they are administered through patches rather than syringes, they could be made to be biodegradable, cutting down on hazardous medical waste and making vaccine transport easier.  Furthermore, the microneedles are painless, potentially improving acceptance of vaccinations.

Most importantly, however, vaccines based on DNA or a dried live-virus do not require cold storage, but can be kept at room temperature.

The cost and energy requirements of the cold chain are a large burden on health facilities, especially those without access to reliable power.  Remote or underserved health facilities are often the last link in the cold chain, delivering vaccines to high-risk populations.  Any weak links in the cold chain, throughout transport and storage, will compromise the effectiveness and safety of vaccines as well as the large-scale campaigns to distribute them.

In small health facilities, for example, the vaccine refrigerator can represent more than half of the total electricity load and daily consumption.  In addition to the electricity costs of cold chain refrigerators, the equipment itself is expensive, costing several hundred to several thousand dollars depending on their size and capabilities.

Even with appropriate refrigeration, the cold chain is at risk if power supplies are unreliable or backup power is not available.  While most refrigerators (especially ice-lined refrigerators) have some holdover time where temperatures can be maintained without power, the most robust cold chain solutions involve power supply and backup power systems.

In Haiti, the Improving Health Facility Infrastructure (IHFI) project has installed many such backup systems at hospitals around the country.  These systems consist of battery banks and inverters which store and supply power for frequent power outages.  In Guyana, IHFI is installing PV systems to run loads and cold chain refrigerators at rural health outposts.

Such systems are critical not only for the cold chain, but also for laboratory equipment and other essential health facility loads.  Implementing and maintaining them, however, is expensive and requires training and institutional support.

Even if vaccination technologies like these someday prove safe and effective for humans, there will still be a need for the cold chain for other medical products, like blood, for instance.  However, any opportunity to reduce the need for the cold chain will simplify not only the delivery of vaccines but also the energy systems that support that delivery.  

The cold chain is a major hurdle for vaccination campaigns and a significant load on hospital energy systems.  While the vaccine developments highlighted here are only in the early stages of development, the potential for overcoming that hurdle and expanding the effectiveness and coverage of HIV, TB and other vaccines is clear.

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