The Vaccine Cold Chain in North Korea: Assessing the Capacity to Store Routine Vaccines and Potential to Support Pandemic Vaccination Activities

Abstract

Background

The health system's capacity to store vaccines in North Korea has been less studied. In this study, we aimed to investigate if the current vaccine cold chain in North Korea can store routine vaccines and if it has the storage capacity to handle pandemic vaccination activities (PVAs) without interrupting the country’s successful routine immunization program.

Methods

We used tables extracted from an evaluation report of The Global Alliance for Vaccines and Immunization (GAVI)’ Health Systems Strengthening program in North Korea from 2007 to 2014. We then used the World Health Organization’s Immunization Supply Chain Sizing Tool to estimate gaps and the cost of scaling up cold chain storage.

Results

We found that the vaccine cold chain in North Korea has adequate storage capacity for routine vaccines. While we found a deficit of 7,172 L at the central medical warehouse (CMW) and 14,256 L at the provincial medical warehouses (PMWs), the storage at the county warehouses (CoMW) had a surplus. When assessed for PVA, we found an aggregated deficit of 115,574 L (CMW), 113,160 L (PMW), and 25,133 L (CoMW). To fill the gaps, investments of 229,917 USD, and 2,262,211 USD were estimated for routine and PVA vaccination programs, respectively.

Conclusion

As countries and the international community work to improve systems in preparation for future pandemics, there is a need to scale up the North Korean vaccine cold chain to a pandemic-ready state.

Graphical Abstract

INTRODUCTION

During and after the coronavirus disease 2019 (COVID-19) pandemic, a growing body of literature has assessed if most countries can immunize their population and have found that several countries lacked adequate cold chain storage capacities.1,2,3 Specifically, previous studies have questioned the ability of low- and middle-income countries to store vaccines that do not require ultra-low temperature (ULT) equipment.2,3

North Korea’s healthcare system has been previously studied. Despite the common negative views, some research indicated a strong, reliant, and functional system operating as a four-tiered healthcare delivery system including 133 tertiary care facilities, 1,608 secondary care facilities, 6,263 primary healthcare facilities, and over 45,000 household doctors.4,5 North Korea has previously recorded good effective vaccine management (EVM) scores which were mostly above the global threshold of 80% for cold and dry storage capacity (91%) and buildings, cold chain equipment, and transport (87%) in 2016.6 Only China, Mongolia, and Vietnam had comparable scores from the East Asia and Pacific region of the United Nations Children Fund (UNICEF). These indicators indicate that North Korea may have an adequate cold chain system to store routine vaccinations. However, questions remain over whether the country has the capacity to store supplementary vaccines. Although data related the vaccine cold chain in North Korea are scarce, some previous reports in affirmation with the EVM scores indications have shown that the vaccine cold chain system of North Korea is effective and highly functional for the storage of routine vaccines.5,7 There also were improvements in the cold chain system through the Global Alliance for Vaccines and Immunization (GAVI)-funded Health Systems Strengthening (HSS) program since 2007 (Table 1).7

Table 1. GAVI Health Systems Strengthening Program installed cold chain equipment.

Equipment		Location				Quantity
		Central	Provincial	County	Ri
Cold storage
	Cold room (40 m3)	✓				4
	Cold room (10 m3)		✓			11
	Freezer room (20 m3)	✓				1
	Ice lined refrigerator	✓	✓	✓	✓	472
	SDD			✓	✓	1,406
	Cold box	✓	✓	✓	✓	1,175
	Carrier	✓			✓	9,811
Power
	Generator (50 kW)	✓				2
	Generator (10 kW)		✓			22
	Voltage Regulator (120 kW)	✓				1
	Voltage Regulator (70 kW)	✓				1
	Voltage Regulator (10 kW)		✓			22
	Voltage Regulator (2 kW)	✓	✓	✓	✓	448
Temperature Monitoring
	Fridge tag 2	✓	✓	✓	✓	2,880
	Multi log 2	✓	✓			17
	Freeze tag	✓	✓			5,900
Transport
	Refrigerator vehicle	✓				2
	Truck		✓			11
	Motorcycle			✓	✓	110
	Motor tricycle			✓	✓	318
Others
	Tool kit for SDD installation	✓	✓			24

SDD = solar driven drive.

Source: Evaluation of the GAVI Health Strengthening Support to the Democratic People’s Republic of Korea. All locations are assumed to be administrative-level specific medical warehouses.

While previous reports have commended North Korea’s ability to deploy vaccines quickly, recent statements by the Ministry of Public Health of North Korea and GAVI suggest a more systematic and model-based approach using a cascade deployment methodology.4,8,9,10 A 2018 review by the WHO regional office for Southeast Asia revealed that in North Korea, vaccines are transported monthly from the central medical warehouse to provincial medical warehouses, then monthly from the provincial medical warehouses to county medical warehouses, and to the ri/dong vaccination points on the day or the day before vaccination (Fig. 1).9 A recent WHO report detailed that during a recent nationwide catch-up immunization campaign in North Korea, vaccines were delivered to county-level medicine warehouses and then to immunization units at ri/dong clinics in the necessary daily quantities and all other immunization supplies were distributed directly to the immunization sites earlier in 2023.11

Fig. 1. The vaccine deployment strategy used in North Korea.

There is limited and inconclusive academic literature on the cold chain capacity of North Korea’s capacity to store supplementary vaccines without disrupting Expanded Program on Immunization (EPI) vaccination programs. It has been suggested that the cold chain in North Korea was sufficient for the rapid deployment of supplementary vaccines.5 Biersteker and colleagues12 also indicated that North Korea could store and transport COVID-19 vaccines at 2°C to 8°C, and believed that the country could deploy ULT vaccines, including mRNA vaccines if used within 30 days. These claims have been the subject of controversial debate in previous media reports. A 2021 report argued that while North Korea’s cold chain system could handle EPI and supplementary vaccines, it might fall short incase ULT vaccines were deployed. Specifically, it suggested that the existing infrastructure could not manage Pfizer and Moderna vaccines, but did not question its capacity to handle AstraZeneca or Sinovac vaccines.13 Moreover both scholars argued that the available cold chain system can ably store supplementary vaccines that require 2–8°C yet both did not use any statistical measurements to assess if this was true.12,13 However, during the pandemic when the South Korean government offered to provide vaccine aid, experts questioned the capacity of the North Korean vaccine cold chain to store the COVID-19 vaccines.14

However, none of the studies above has estimated the available cold chain and its capacity to store EPI and supplementary vaccines. The studies also do not discuss the equipment needed to improve the cold chain and they do not conclude on the question of whether or not the existing cold chain capacity has the capacity to adequately keep EPI vaccines alongside supplementary immunizations. This study aimed to answer these questions and add to a rare body of literature about the North Korean health system, its capabilities, and the need for storage and handling of vaccines.

METHODS

Data sources for existing equipment

The data used in this study was extracted from tables and pictures in the report of the evaluation of the GAVI HSS support to the Democratic People’s Republic of Korea published in 2018.7 The report is well-known for providing comprehensive information about the cold chain system in North Korea, giving clearer locations of installed cold chain equipment that GAVI has installed in North Korea since 2007. This equipment is shown in Table 1. In addition to the GAVI HSS reports, this article utilizes the WHO immunization supply chain sizing tool to estimate the existing cold chain storage capacity and its capacity to store vaccines at the central, provincial, and county levels. We also estimate additional storage capacity needed to store supplementary vaccinations modeling a scenario in which a 95% coverage of AstraZeneca coronavirus vaccine inoculation could be achieved without disrupting the existing routine vaccinations and the estimated cost of upgrading the existing cold chain system.15

Equipment distribution

As shown in Table 1, equipment distribution was estimated using shown placement in the HSS report.7 The distribution of equipment where the type had been supplied at different levels was done following the gaps pointed out at each level by the North Korean government in their application for HSS 2 (2014-18) where they identified the impact of the equipment placed in HSS 1 and where could be strengthened in HSS 2.10

Measurement of equipment storage capacities

Equipment storage volumes were referenced from the WHO performance, quality, and safety (PQS) tool16 and the WHO immunization supply chain sizing tool.15 To establish the equipment type, we considered previously used equipment in countries found in temperate regions and where no applicable equipment was found to match the specifications of temperate regions, we took examples from previous GAVI equipment installations in the WHO Southeast Asia region.17 Vaccines were assumed to be supplied in four supply intervals with the storage maintenance the recommended 25% safety stock included. Other assumptions made in the estimation of vaccine storage volumes are shown in supplementary materials (Supplementary Tables 1 and 2). Vaccine volume calculations in the WHO immunization supply chain sizing tool follow guidelines set in the WHO vaccine management handbook (Module VMH-E3-01.1).18

The immunization system in North Korea

Estimating vaccine storage needs in North Korea required an assessment of the population at all levels within the vaccine supply chain (Supplementary Fig. 1). The national immunization services system details the hierarchy of vaccine logistics overseen by the Ministry of Public Health.7,9 This hierarchy begins at the central medical warehouse and extends to the provincial medical warehouses, then to the county medical warehouses, and finally to the vaccination units at ri/dong clinics. North Korea has one central medical warehouse in Pyongyang, 10 provincial medical warehouses, 208 county medical warehouses, and 6,263 ri/dong clinics, which serve as the primary vaccine administration points in the country (Fig. 1).

Population estimation

The population of North Korea was estimated using World Bank population estimates and projections where a total population of 26,069,416 was estimated for North Korea in 2023.19 This population was allocated as the target population of the central medical warehouse. To decentralize the population, we utilized population distribution results from the North Korean 2008 census20 to estimate the provincial-level population distribution, which was then divided by the number of counties to establish the average population in every county depending on the province it was located in. An elaborate preview of these estimates is included in supplementary files (Supplementary Tables 3 and 4).

Storage and cost estimation

This study was conducted using the WHO immunization supply chain sizing tool (hereafter sizing tool). The tool was designed by the WHO in 2021 for “national program managers to estimate the size of the required supply chain infrastructure for vaccine storage and transportation at each level and facility.” 15 It is freely downloadable as an Excel file in the WHO catalog of all vaccine supply chain tools. The tool allows for entering data about the vaccines being covered by the EPI, including the vaccine coverage targets, a selected vaccine wastage rate, storage points and their volume, population levels at different decentralized levels, and after the automatic calculations are done, a selection of needed equipment to cover the cold chain capacity deficit is made. Data entered is attached in the supplementary materials (Supplementary Table 5).

The routine vaccine required volumes were estimated by using the target group which is a percentage of the total population that is to be inoculated. In this case, we measured the percentage of the population which was of the age included in the United States Centers for Disease Control’s recommendations outlined in the Child and Adolescent Immunization Schedule.21 The population in each age range was taken from the World Bank population estimates.19

The volumes were automatically generated with consideration of the doses needed, packed tertiary and secondary storage needs, the vaccine wastage figures and their wastage factor. And the estimation presented in liters.

After this, the assumed distribution was also estimated in liters as per WHO PQS estimation per equipment at all three warehouse levels and the surplus and deficits were presented. A similar estimation method was used for supplementary vaccines.

The deficit storage was then converted into equipment whose prices are included in the WHO immunization supply chain tool in order to estimate the cost of upgrading the cold chain system.

The quantification process of the tool

The tool works with linked Excel tabs that capture vaccine coverage, utilization factors, wastage levels, safety volumes, and the current storage of all levels in an editable hierarchy and uses WHO’s vaccine volume calculation guidelines18 to produce graphs that compare current storage capacity against the entered population’s needs to estimate gaps in the inventory in a separate tab for routine and that of supplementary vaccines. The tool has been previously used in Kosovo for their cold chain system assessment.22

RESULTS

Cold chain storage capacity

Table 2 shows the assumed distribution storage equipment across the central medical warehouse, provincial medical warehouses, and county medical warehouses. Our findings indicated that the central medical warehouse had storage space amounting to 39,051 L at 2–8°C, and 5,520 L at −25 to −15°C (Table 2). provincial medical warehouses had a total of 33,330 L at 2–8°C, and county medical warehouses were estimated to have a total of 102,480 L of storage capacity.

Table 2. Assumed distribution of vaccine cold chain storage equipment in North Korea.

Equipment		Location			Total
		Central	Provincial	County
Cold room (40 m3)		4			4
Cold room (10 m3)			11		11
Freezer room (20 m3)		1			1
Ice lined refrigerator			11	420	431
Solar driven drive				420	420
Total storage at each administrative level
	At 2–8°C	39,051 L	33,330 L	102,480 L	174,861 L
	At −20°C	5,520 L	-	-	5,520 L

Capacity for routine vaccines

Table 3 shows the available, needed, and gaps in storage capacity in the cold chain. Results showed that routine vaccines needed 46,223 L of cold chain storage space at 2–8°C which was higher than the estimated available 39,051 L suggesting that that there was a deficit of 7,172 L at the central medical warehouse. At provincial medical warehouses, we found out that only 3 provincial medical warehouses in Ryanggang, Kangwon, and Jagang indicated adequate storage capacity for routine vaccinations.

Table 3. Current, needed, and gap in vaccine cold chain storage for routine vaccines in North Korea.

Warehouse	Available storage	Volume of vaccines, L	Gap in storage, L
Central medical warehousea	39,051	46,223	−7,172
Central medical warehouse total	39,051	46,223	−7,172
Ryanggangb	3,333	1,424	−1,909
North Hamgyongb	3,333	4,608	1,275
South Hamgyongb	3,333	6,069	2,736
Kangwonb	3,333	2,979	−354
Jagangb	3,333	2,575	−758
North Phyonganb	3,333	5,403	2,070
South Phyonganb	3,333	8,020	4,687
North Hwanghaeb	3,333	4,225	892
South Hwanghaeb	3,333	4,530	1,197
Pyongyangb	3,333	6,443	3,110
Provincial medical warehouse total	33,330	46,276	12,946

Gap in Storage = Volume of Vaccines – Available Storage.

^aCentral Medical Warehouse.

^bProvincial Medical Warehouse.

All the other provincial medical warehouses had deficits in needed storage volume, particularly in South Phyongan where the highest estimated deficit of 4,687 L was found. When totaled, the total available vaccine cold chain in all provincial medical warehouses was 33,330 L at 2–8°C, which was less than the needed 46,276 L at the provincial level to store routine vaccines indicating that a deficit of 12,946 L was observed at that level. The combined available cold storage volume at the county level is 102,480 L, surpassing the needed 11,906 L to store routine vaccines (Supplementary Fig. 2).

Cost of upscale for routine vaccines

The supply chain tool was used to estimate that an additional walk-in cold room (WICR) of 40 m³ was needed at the central medical warehouse. Provincial medical warehouses were also estimated to need 1 each of WICRs of 20 m³, 15 m³, and 10 m³. Our results indicated that these tools would be worth 216,287 United States Dollars (USD), consume annual energy worth 9,567 USD, and need annual maintenance of 3,720 USD. This makes the estimated initial investment of 229,574 USD that would scale up the current cold chain at central, provincial, and country levels to reach the needed capacity to adequately store routine vaccines (Table 4).

Table 4. Cost estimation for needed equipment to increase the storage capacity for routine vaccines in North Korea.

Cold chain storage equipment		Vaccine stores		Total No. of equipment	Total cost estimation
Type	Type of equipment	CMW	PMW		Equipment cost	Annual energy consumption	Annual maintenance
Cold rooms		1	3	4	$190,737	$8,532	$2,861
	WICR-10 m3	-	1	1	$39,584	$1,267	$594
	WICR-15 m3	-	1	1	$43,028	$1,795	$645
	WICR-20 m3	-	1	1	$46,389	$2,218	$696
	WICR-40 m3	1	-	-	$61,736	$3,252	$926
Refrigerators		-	15	15	$18,810	$683	$658
Ice lined refrigerator		-	15	15	$18,810	$683	$658
Freezers		-	14	14	$5,740	$351	$201
Freezers compression		-	14	14	$5,740	$351	$201
Total cost					$216,287	$9,567	$3,720

CMW = central medical warehouse, PMW = provincial medical warehouse, WICR = walk-in cold room.

Capacity for supplementary vaccines

We assessed the current capacity of North Korea’s cold chain system to store supplementary vaccines while maintaining routine vaccination schedules. Assuming 95% coverage, we modeled the storage requirements for AstraZeneca’s COVID-19 vaccine (AZD1222). The central medical warehouse was estimated to require 115,574 L of storage between 2°C and 8°C. Similarly, provincial medical warehouses and county medical warehouses each required 115,707 L of storage capacity. Given deficits in central medical warehouse storage capacity for routine vaccines, an additional 115,574 L of storage was needed to avert the deficit.

At the provincial medical warehouses, the required additional storage varied significantly, ranging from 1,808 L in Ryanggang to 20,052 L in South Phyongan, and a total 113,160 L at the provincial level (Fig. 2A). Conversely, all county medical warehouses had surplus storage capacity after accommodating routine vaccines, totaling 90,574 L. This left a deficit of 25,133 L among them (Fig. 2B).

Fig. 2. Estimation of the available and needed additional cold chain storage for storage of supplementary vaccines at provincial- and county-level medical warehouses. (A) Provincial-level estimation. (B) County-level estimation.

Cost of upscale for supplementary vaccines

The deficits at all levels, when needed storage requirements were assessed, indicated a need to estimate the equipment needed and their cost to scale up the cold chain storage at all levels. The large deficit led to the estimation that a total of 35 WICRs and 271 ice-lined refrigerators (ILRs) would be needed to scale up on the cold chain in North Korea. Thirteen of 40 m³ WICRs would be needed for the central medical warehouse, and 258 more ILRs needed at the county medical warehouses.

An investment of 2,221,688 USD was estimated for equipment purchase, annual energy costs totaling 29,222 USD, and annual maintenance costs totaling 10,024 USD were also estimated (Table 5).

Table 5. Cost estimation for needed equipment to increase the storage capacity for supplementary vaccines in North Korea.

Cold chain storage equipment		Vaccine stores			Total No. of equipment	Total cost estimation
Type	Type of equipment	CMW	PMW	CoMW		Equipment cost	Annual energy consumption	Annual maintenance
Cold rooms		13	22	-	35	$1,883,108	$25,822	$7,062
	WICR-15 m3	-	8	-	8	$344,224	$3,971	$1,291
	WICR-20 m3	-	3	-	3	$139,168	$1,840	$522
	WICR-30 m3	-	11	-	11	$597,151	$8,319	$2,239
	WICR-40 m3	13	-	-	13	$802,565	$11,692	$3,010
Refrigerators		-	12	258	271	$338,580	$3,400	$2,963
Ice lined refrigerator		-	12	258	271	$338,580	$3,400	$2,963
Total					306	$2,221,688	$29,222	$10,024

CMW = central medical warehouse, PMW = provincial medical warehouse, CoMW = county medical warehouse.

DISCUSSION

Our study explored existing data on the state of the cold chain system in North Korea, identifying attained equipment from GAVI and estimating of the equipment’s volume, its distribution, and its ability to store all vaccines in the EPI, as well as its ability to store additional vaccines in supplementary immunization campaigns. Our findings emphasized that the current vaccine cold chain in North Korea can manage EPI vaccines. However, we identified gaps at the central and provincial levels that can be closed with minimal investment. In addition, the gaps widened when we considered supplementary vaccines, exceeding the available cold chain storage at all levels including the county warehouses. This highlights the need for an estimated investment of approximately 2.2 million US dollars in storage equipment to facilitate mass vaccinations for 95% of the population, while ensuring uninterrupted routine vaccination schedules.

The vaccine cold chain in North Korea was developed mostly with help from the GAVI HSS program from 2007.7 The partnership between the government of North Korea and GAVI dates back to 2001, following initial engagements with UNICEF plus the WHO in 1996.23 This led to the development of a financial stability plan for immunization in 2003, and successful introduction of hepatitis B vaccines in the same year and the widely known measles immunization campaign in 2007.24 Since then accelerated efforts to improve the cold chain system in North Korea started with nation-wide surveys for cold chain and routine vaccine coverage leading to the extension of the cold chain system to the county level in 2010.24 Moreover, the current vaccine cold chain in North Korea was improved with support from GAVI in partnership with the North Korean government and other development partners.9,24

Evidence suggests that North Korea has achieved high coverage rates in its EPI, with reported rates of 97–98% for eight major vaccines in 2017, a trend that had remained stable since 2007. Notably, there has been a remarkable increase in coverage for Pentavalent vaccines, rising from 93% (Penta1) and 92% (Penta3) in 2007 to 98% and 97%, respectively in 2017.9,25 This happened even when the country used a one-day-in-a-month vaccination system rather than an outreach method.9 These findings indicate the effectiveness of the existing cold chain infrastructure in facilitating successful vaccine delivery. However, reports indicate a decline in these coverage figures during the coronavirus pandemic between 2020 and 2022.25

Results indicated that the vaccine cold chain in North Korea could not handle incoming supplementary vaccines. Despite achieving nearly complete coverage up to the county level during the GAVI HSS initiative, the cold chain system was not adequate for storage of supplementary vaccines. This highlights the urgent need to expand and strengthen the vaccine cold chain to prepare for pandemics similar to COVID-19. Concerns about North Korea's capability to handle COVID-19 vaccines have previously been raised, particularly regarding their infrastructure’s ability to manage mRNA vaccines requiring ULTs.13 Scholars have noted that North Korea’s cold chain may effectively handle vaccines like AstraZeneca and Sinovac, which require temperatures between 2°C and 8°C.5,12,13 However, our study found that this could also not be achieved if the routine vaccination programs had been assumed to be ongoing at the same time.

Our findings suggest that North Korea’s existing cold chain equipment can store routine vaccines but not support supplementary vaccination campaigns concurrently. This challenge mirrors issues faced by other low- and middle-income countries (LMICs) during the COVID-19 pandemic, where insufficient cold chain capacity hindered vaccine supply.26 Countries eligible for GAVI support, including North Korea, have received additional funding for infrastructure development through GAVI’s Cold Chain Equipment Optimization Platform (CCEOP) since 2016.27

In the context of North Korea, our study indicates that the vaccine cold chain system operates at maximum capacity at the national and provincial levels during routine vaccination campaigns. Introducing vaccines like AstraZeneca could potentially strain the system, leading to shortages similar to those experienced by other LMICs.

During the COVID-19 pandemic, the GAVI-coordinated COVAX initiative emerged as a pivotal platform for global vaccine sharing, ensuring secure procurement and distribution of vaccines to 195 countries and territories. COVAX provided free vaccine doses and equipment to 92 LMICs from its $12 billion fund pool.28 However, during this period, North Korea had closed its borders and did not report any cases of coronavirus until 2022.23 This coincided with the North Korea Sanctions and Policy Enhancement Act of 2016 and Executive Order 13810 of 2017,29 both imposing sanctions on North Korea’s nuclear program, which restricted international exchanges. Reports also indicated that North Korea did not reach an agreement with COVAX regarding potential vaccine assistance in 2021.23 These factors likely contributed to the international community’s inability to support North Korea in its fight against COVID-19 and thus the cold chain system’s capacity to store these vaccines has not been studied or reported in detail by the international actors like GAVI or UNICEF.

Further challenges raised to the vaccine cold chain include the need for heating of vaccine rooms at the Ri and county levels where vaccine temperatures drop below −15°C in the winter. There also remains a challenge of electricity supply in some areas which have recorded to receive around 2 to 4 hours of electricity every day.9

The strengths of this study include the use of a WHO-commissioned methodology to check on the gaps and needs of the cold chain system in North Korea. Our research also focuses on using existing literature to extract usable statistics including the modeling of population and equipment distribution across levels in the country. To our knowledge, this is the first study to assess the cold chain system in North Korea using a statistical tool.

The research however shares common limitations with previous studies that have attempted to study the healthcare system in North Korea.24 First, the documents from which the data was extracted are until 2014, yet there is evidence of further interventions between GAVI and the North Korean government to date, including a UNICEF waiver that supplied cold boxes to the country in 2021.30 Additionally, the distribution of the equipment is based on many assumptions made including the equal distribution across all facilities of the same level. This assumption, however, did not affect the results in a significant way, since all the levels still had deficits in storage. This study also did not investigate the cold chain capacity at the ri/dong level where the country has previously noted its largest deficits in cold chain storage. We also only focused on the storage component of the cold chain system, which includes other components like transport, electricity supplies, temperature control tools, among others.

North Korea’s vaccine cold chain storage capacity could be adequate for the routine vaccines in the EPI programs. Nonetheless, small gaps remain that could be closed with minimal investments. However, to prepare for future pandemics, the North Korean government and the international community will need to step up and increase the available storage. There also exist challenges due to minimal ULT equipment which need to be studied, but our observation indicates that ULT-needing mRNA vaccines would require larger investments to be administered in North Korea.

SUPPLEMENTARY MATERIALS

Supplementary Table 1

Assumptions made when estimating storage capacity at different administrative levels

Supplementary Table 2

Refrigerators and solar direct drives assumed to be used in North Korea

Supplementary Table 3

Population estimates according to the 2008 census

Supplementary Table 4

Population estimations using 2022 population estimates

Supplementary Table 5

Assumed vaccine coverages, their volumes, prices and wastage

Supplementary Fig. 1

North Korea’s immunization administrative flow chart.

Supplementary Fig. 2

County-level cold chain storage available and volume of vaccines in the routine vaccination programs.