Puerto Rico is leading COVID-19 vaccination efforts in the United States, with 89.7% of adults already fully vaccinated (1). However, many other regions are struggling to gain that level of traction, if any. Less than 1% of people in developing countries are fully vaccinated (2). Because Pfizer–BioNTech’s and Moderna’s respective mRNA-based SARS-CoV-2 vaccines still require ultracold temperatures for long-term storage, vaccine distribution in remote locations is arduous without appropriate cold-chain infrastructure.

Puerto Rico’s success in vaccinating its population demonstrates how flexible ultracold solutions could mitigate many cold-chain inconsistencies in rural and underserved regions. When determining how to improve vaccination rates in such communities, we must examine both obstacles to access and strategies for improving cold-chain systems.

Cold-Chain Obstacles in Developing Nations
Remote communities in developing nations lack long-term solutions for receiving and storing vaccines. Inconsistent access makes it difficult to set up permanent inoculation sites and create stable vaccination schedules. People from low-income regions also face substantial transportation barriers. In least-developed countries (LDCs) such as Nepal and Uganda, more than 80% of residents live in rural districts, often in areas that are prone to natural disasters (3). Utilities also remain underdeveloped in such communities, with more than half of residents lacking access to electricity (4). Although ultracold storage could help to overcome such hurdles to vaccination, most ultralow-temperature (ULT) solutions are nonoperational in remote territories.

Traditional Distribution Methods
Conventional ULT freezers for pharmaceutical storage are large and difficult to maneuver. They require regular maintenance to prevent excessively warm temperatures from compromising vaccine integrity. Often compressor based, they have power requirements that make them inoperable in regions without reliable sources of electricity.

Alternatively, dry ice can maintain ultracold temperatures, but this solution is only ideal for short-term transportation and storage. Once dry ice begins to sublimate, it must be replenished immediately to ensure that materials are kept at their specified temperatures. Considering the significant amount of energy needed to produce and preserve dry ice, it simply is not an option for long-term storage in underserved communities. Instead, such regions need cold-chain solutions that can provide ongoing ULT operation while withstanding long-distance travel.

The Key to Mitigating Cold-Chain Inconsistencies
Flexible and adaptable vaccination strategies are critical in countries with limited resources and poor environmental conditions. A “hub-and-spoke” model like the one that Puerto Rico leveraged in its vaccine distribution strategy is ideal in locations that cannot set up manufacturing facilities. In this distribution paradigm, vaccines are delivered to a central site and stored in a large ULT freezer powered by a primary or backup generator. From there, they are transferred to portable ULT freezers and distributed to remote locations. Mobile ULT freezers that plug into USB ports are helpful for such steps because they can be powered during shipment by air or automobile.

Although cost remains a significant barrier for implementing such strategies, enterprises and nonprofit organizations are partnering with solution providers to donate freezers to developing regions. Like Puerto Rico, the United Parcel Service (UPS) has established “freezer farms” in Singapore, leveraging portable ULT freezers to inoculate communities in Southeast Asia. As part of the COVAX initiative, UNICEF is advancing efforts to procure and supply COVID-19 vaccines for more than 100 countries.

Toward Vaccine Equity
Inequitable vaccine distribution remains the biggest challenge on the road to global immunization. However, a strategic distribution approach based on flexible ULT solutions could move the world closer to boosting vaccination rates in underserved areas. Beyond COVID-19, progressive cold-chain improvements also could help to address other infectious diseases — e.g., Ebola — that continue to spread rapidly in such regions.

References
1 Cueto I. Mandates. A Well-Organized Campaign. No Politics. How Puerto Rico’s Vaccine Drive Turned into a Success. STAT 3 November 2021; https://www.statnews.com/2021/11/03/mandates-a-well-organized-campaign-no-politics-how-puerto-ricos-vaccine-drive-turned-into-a-success.

2 Maxmen A. The Fight to Manufacture COVID Vaccines in Lower-Income Countries. Nature 15 September 2021; https://doi.org/10.1038/d41586-021-02383-z.

3 Dillinger J. Rural Population By Country. WorldAtlas 25 April 2017; https://www.worldatlas.com/articles/working-on-the-land-the-world-s-major-rural-populations.html.

4 Over Half of the People in Least Developed Countries Lack Access to Electricity. United Nations Conference on Trade and Development: Geneva, Switzerland, 1 July 2021; https://unctad.org/topic/least-developed-countries/chart-july-2021.

Shea Vincent is senior marketing director at Stirling Ultracold, 6000 Poston Road, Athens, OH 45701; https://www.stirlingultracold.com.