Forecasting, Preparation and Innovation

According to the World Health Organization, vaccine products should be transported and stored between 2°C and 8°C.  Exposure to adverse heat can cause the loss of vaccine potency. Maintaining the specified temperature requires a thermal-controlled cold chain.  Building an efficient network of equipment and procedures to preserve vaccines’ potency has always been a problem in the cold supply chain. 

The World Health Organization initiated the Expanded Programme on Immunization (EPI) more than 30 years ago, aiming to immunize at least 90 percent of children around the world. Ever since then, cold chain models have evolved, but many challenges come with innovation. 

temperature sensitive vaccines chart

Geographical obstacles, government bureaucracy, mismanagement and lack of utilities are among the problems that continue to haunt the cold chain sector. 

Implementing the Expanded Programme on Immunization in low-and middle-income countries resulted in increased vaccine volume handled by health personnel. While this development reflects the immunization program’s progress, it also strained the cold chain supply system.

The WHO and pharma cold chain sectors had infused investments into cold chain equipment (CCE) to improve vaccine logistics in developing countries.  Manufacturers created tools to aid public health program managers to document inventories and forecast sector needs. Despite these initiatives, the industry is still developing accurate models to assess the cold chain sector and provide reliable forecasts. 

Forecasting the demand for freezer-safe vaccine carriers is important in the cold chain sector.  Forecasting enables health agencies and governments to prepare for possible problems and gives them some lead time for innovation. Without forecasting, vaccine programs would be at the mercy of circumstantial influences that could impede immunization initiatives worldwide.

PATH’s Initiative: Installation of Base and Forecasting Model

Program for Appropriate Technology in Health (PATH), an international nonprofit global health organization, initiated programs to formulate a model to assess CCE needs.  In an initial step, the organization examined CCE inventories to know what equipment was in use at the national and subnational levels during storage, transportation and the vaccination outreach. By doing this, PATH began the process of creating a forecasting model. 

In the next step, PATH estimated each country’s yearly vaccine supply volume by using the information from routine immunization schedules and planned vaccine outreach for the year.Explaining further the steps and action in countries with no data, an excerpt from a PATH study states: 

This is the needs portion of the model. Finally, the installed base cold chain capacity is compared with volume needs to identify a surplus or shortage of capacity in the cold chain—generating the forecasting portion of the model. For countries with no data, the model calculates future capacity needs and assumes zero existing capacity. Capacity shortages are then aggregated at the country, regional, or global level and translated into equipment forecasts. To refine assumptions or prioritize specific areas of needs, each forecast can be further segmented by WHO or United Nations Children’s Fund (UNICEF) region, Gavi country eligibility, or other filters

PATH, Forecast Report: Freeze-Safe Vaccine Carriers. Page 4
Source: PATH, Forecast Report: Freeze-Safe Vaccine Carriers



Using the available CCE data for each country, PATH calculated the country-level storage, transport, and outreach capacity by using this formula:

Number of units × equipment capacity

As expected, more detailed information on equipment use resulted in more accurate CCE inventory data. When such information is not available, however, assessors used the range of lower, average and upper-bound capacities for each country. They based the estimation on the minimum, average, and maximum totals of equipment models. 

When detailed equipment data were not available, the average vaccine storage volume by equipment technology class was the default value. 

Source: PATH, Forecast Report: Freeze-Safe Vaccine Carriers

Annual Need

PATH’s formula for calculating country-level vaccine volume:

Target population × number of doses × (packed vaccine volume + packed diluent volume) × coverage rate × wastage factor × 1L /1,000 cc

According to PATH, the target population generally comprises births or surviving infants, but may also include a specific target population for a vaccine. The global annual need is the summation of all yearly vaccine country needs.

Future needs (needs-based forecast): by country

To calculate country-level estimates of capacity shortages or surplus across each cold chain segment, the formula is:

Current capacity – projected capacity needed in the forecast year

Freeze-safe Vaccine Carriers Forecast Summary 

Public health managers can protect vaccines from the damaging effects of freezing temperature by modeling the potential global market, to avoid temperature excursions due to overstocking or mishandling of vaccine stocks. A study made by PATH showed that UNICEF has an annual vaccine procurement worth $70 million, approximately 70% of which are freeze-sensitive.  

Inefficient carriers not only put vaccines at risk but lives as well—damaged vaccines due to exposure to adverse temperature results in financial loss and health risks to vulnerable recipients. 

Vaccine Storage, Transport and Delivery

The risk of damaging vaccines during storage, transport, and delivery is higher in low- and middle-income countries, especially in subnational areas that lack roads, dependable cold chain, and local government support. In most cases, health workers deliver vaccines in cold boxes lined with frozen packs. 

Although such a delivery model is sufficient, it puts the vaccines at risk due to unstable temperatures.  Rural clinics in far-flung areas lack power supplies for refrigeration and cold systems. 

Freezing temperatures pose as much risk to vaccines as heat, because the vaccines may contain alum adjuvants, an ingredient that increases sensitivity to freezing. Although that element strengthens the vaccine antigen’s immunogenicity, it compromises potency upon exposure to adverse temperatures. 

According to some studies, between 75% to 100% of vaccine shipments are exposed to unstable freezing temperatures in cold chains.  Areas with a lack of adequate power supply result in cold chain “breaks” that put the vaccines at risk during temperature change.  In some cases, health workers fail to validate vaccines’ potency after exposure, and jeopardize immunization effectiveness. 

WHO Guidelines and Carrier Technology

The World Health Organization recommends using conventional carriers with cold water packs rather than frozen ice packs to prevent vaccine exposure to freezing temperatures. Frozen ice packs require pre-conditioning to warm the packs to 0°C, but the process is hard to calibrate accurately.  

An assessment revealed that cold boxes lined with ice packs expose vaccines to freezing temperatures when carriers don’t adhere to proper conditioning.

To remedy this, PATH introduced a technology that enables freeze-safe barriers between the ice packs and the vaccine vials, thus decreasing the risk of exposure to adverse temperatures.  

The World Health Organization issued Performance, Quality and Safety (PQS) standards for freeze- safe vaccine carriers to decrease the risk of vaccine potency loss.  With these guidelines, WHO emphasized the importance of maximizing the market impact of freeze safe vaccine carriers and understanding the market. 

Looking Ahead: The Potential Market

Researchers used PATH’s Installed Base and Forecasting model by combining the existing number of carriers from 73 Vaccine Alliance (Gavi) member-countries. They projected the number of freezer-safe carriers required to meet the needs of a projected population scheduled for vaccination through 2020.

PATH explains their forecasting model:

Since current vaccine carriers do not have freeze-safe capabilities, the replacement of installed base units assumes a 1:1 ratio of conventional carriers to new freeze-safe ones. The number of additional freeze-safe vaccine carriers needed was calculated using a scenario analysis that leveraged key assumptions on the percentage of routine immunizations administered via outreach activities and the frequency of these outreach activities per supply cycle. [i]

PATH’s outreach needs formula:

Annual need × % immunization via outreach × 1 / frequency

Source: PATH, Forecast Report: Freeze-Safe Vaccine Carriers

Total Market Forecast

By aggregating net outreach capacity shortages, PATH determined outreach capacity needs at the global level.  The alliance obtained the forecast by dividing global capacity by the average vaccine carrier size, resulting in the number of freeze-safe carriers needed.

Source: PATH, Forecast Report: Freeze-Safe Vaccine Carriers


PATH, Forecast Report: Freeze-Safe Vaccine Carriers, accessed from


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