May 27, 2016 |

When less is more: why intradermal vaccine delivery matters to global health

Novel delivery solutions can help overcome shortages of polio vaccine, ensuring children receive the protection they need.
Health worker weighing baby on a scale.
Babies and young children are weighed and vaccinated at a primary health care center in Nigeria, where polio is no longer endemic, but efforts to curb the virus remain a key public health priority. Photo courtesy of the David and Lucile Packard Foundation.

Sustaining high-immunization coverage is critical to eliminating polio and ultimately global eradication. As countries continue to introduce inactivated poliovirus vaccine (IPV) into routine immunization schedules, strategies for delivering IPV are shifting to better accommodate increases in demand and unanticipated shortages. One approach recently recommended by the World Health Organization (WHO) is the use of a fractional dose of IPV (fIPV), which can be achieved by delivering the vaccine intradermally (i.e., into the upper layers of the skin). However, fractional dosing can be challenging in the settings common to developing countries—that is, until now.

A promising, underutilized delivery route

A woman holds a baby on her lap as a health care worker prepares to give the baby an injection.
Photo: PATH/Carib Nelson.

The skin is an active player in the human immune system, and delivering vaccines or pharmaceuticals directly to it can be more immunologically efficient than injection into the muscle or subcutaneous tissues. So, why is delivery efficiency important?

Hint: it can help vaccinators do more with less.

Research shows that intradermal delivery can, in some instances, achieve the same immunological results as intramuscular or subcutaneous delivery but with 80 percent less vaccine. When supply shortages occur, this could mean the difference between stretching supplies across more patients, or risking that a percentage of those same patients go unprotected from vaccine-preventable disease.

Nevertheless, fractional dosing remains inconsistently used because the injection procedure for achieving it requires considerable training and experience to master with a conventional needle and syringe. Consequently, its impacts have historically been too varied to make it standard practice.

The role of innovation

PATH accelerates the development, delivery, and introduction of vaccines that protect children and communities from disease. Part of this work includes a long history of collaborating with product developers, device manufacturers, and country ministries of health to design, develop, and assess technologies that better enable intradermal delivery. Throughout, our focus has been on vaccines of importance to developing-country immunization programs where fractional dosing has been effective and could help bridge coverage gaps in low-resource settings.

Recently, in close collaboration with the WHO’s Global Polio Eradication Initiative (GPEI), we helped build the clinical evidence base for two fIPV-capable delivery technology solutions, the PharmaJet Tropis disposable-syringe jet injector and West Pharmaceutical Services ID Adapter, which PATH originally developed in partnership with SID Technologies, LLC, then transferred to West in 2013.

Disposable-syringe jet injector.
Disposable-syringe jet injectors, like the PharmaJet Tropis device, use a sterile single-dose syringe and a pressurized liquid stream rather than a needle to administer a fractional dose of inactivated poliovirus vaccine to patients.
A close up of an intradermal adapter used in vaccination.
The PATH-developed West Pharmaceutical Services Intradermal Adapter fits over a traditional needle and syringe like a sleeve, standardizing the injection depth and angle so health care workers can more easily and precisely deliver an intradermal injection. Photo: PATH.

With strong data underscoring the value and effectiveness of each device, the GPEI plans for both to be available by early 2017 to support country use of fIPV—helping ensure supply shortages neither threaten the protection of children and families nor disrupt progress in the global fight against polio.

More delivery solutions on the horizon

PATH and our partners are also helping to advance microarray patches (MAPs) designed to adhere like Band-Aids as they deliver vaccines through the skin. Overall, MAPs hold considerable promise as a thermostable, compact, and integrated (i.e., prefilled) intradermal delivery technology that might even be simple enough for house-to-house volunteers with minimal training to use for vaccinations. Such outreach strategies could be game-changing for polio eradication efforts.

The need for these and other novel delivery technologies are uniquely relevant and important to achieving coverage targets and accelerating progress in public health. After all, a vaccine can mean the difference between a family’s grief and a child’s healthy future.

Darin Zehrung leads the Vaccine and Pharmaceutical Delivery Technologies portfolio at PATH. With Birgitte Giersing from the WHO Division of Vaccine Research, he recently co-delivered the keynote address at the 4th International Conference on Microneedles in London.

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  • Darin Zehrung leads the Vaccine and Pharmaceutical Delivery Technologies portfolio at PATH.