Exploring vaccine storage and delivery

Exploring vaccine storage and delivery
© iStock-Joe_McUbed

HEQ speaks with Thomas Sorensen, Senior Manager at UNICEF, about the cold chain and the challenges facing vaccine refrigeration.

Global charity UNICEF has been delivering immunisation and disease prevention programmes for more than 70 years and is the world’s largest single buyer and distributor of vaccines. Its COVID-19 response programme, launched in early 2020, has reached 153 countries and territories around the world; and the charity has announced its intention to deliver two billion COVID-19 vaccines in the world’s largest-ever immunisation effort.

HEQ speaks with Thomas Sorensen, Senior Manager at UNICEF, about the cold chain and the challenges facing vaccine refrigeration.

How should vaccines be stored and transported in order to preserve the integrity of the cold chain and ensure they remain effective?

The significance of the cold chain is primarily in the name: vaccines need to be kept at the right temperature throughout the entire supply chain. Of course, different vaccines require different temperature conditions, which can present a challenge; but the most pressing issue is in ensuring that the vaccine is kept at the recommended temperature throughout the transport process – this is especially a challenge in warmer regions.

Given that the different types of COVID-19 vaccine require storage at significantly different temperatures, what differing types of equipment will be needed to store and transport each vaccine?

Within the majority of immunisation programmes, vaccines need to be kept under standard temperature conditions of 2°C to 8°C. Again, this can be particularly challenging in desert regions and countries with a hot climate, because that temperature range must be maintained throughout the entire supply chain. There are a number of key fixed points during the transport journey: before the vaccines will be flown out to their destination by the manufacturer, they are packed in different cool boxes which can keep the temperature at the recommended level. Once a package of vaccines arrives at the country where it is to be distributed, it is stored in a cold room at the correct temperature; then it will be transported to a clinical facility, either using cold storage trucks equipped with the technology to keep it at right temperature or cold boxes, which are typically used in cases where vaccines are to be transported to or between lower-level facilities. At each stage in the journey, the vaccines will be placed into a fridge or chiller which has the right temperature conditions; typically the standard cold chain that we operate with in the field is between 2°C and 8°C.

The Pfizer vaccine, which must be stored at ultra-low temperatures between -80°C and -60°C, presents a special situation. However, for the moment this issue applies to a very small proportion of vaccines – it is important to keep in mind that there is much less necessity for specialised logistic operations tailored to the Pfizer vaccine than there is for the standard immunisation supply chains that we would normally operate with as a matter of routing. Pfizer vaccine might deliver something in the range of 100,000 doses per country, which is a relatively small number of vaccines, at least in the initial rounds.

There have been some solutions developed specifically for these vaccines in terms of transportation. Pfizer transports its vaccines using a ‘vaccine shipper’: this is a special cold box designed by the manufacturer, which can keep its contents in ultra-low freezing conditions all the way to the point of entry into the country where is sent. At that point, the shipper can be refilled with dry ice in order to prolong the ultra-low temperature conditions, and then it can retain that temperature for another period of up to two weeks after it is refilled.

There was initially a great deal of focus on these vaccines which need to be stored at ultra-low temperatures, because they were the first to be rolled out; but in terms of the volume of vaccines being released from the different manufacturers, the bulk of vaccines that are coming out now are the ones that require the standard temperature range of 2°C to 8°C. That cold chain is much easier to handle; and there has been a lot of investment in ensuring it can be functional in lower-income regions, so it is probably important to keep that focus on the mainstreaming of the cold chain, rather than on more extreme conditions. We are capable of managing those extreme conditions, but it is also important also to keep the proportions right so that we can focus our strategies and give the appropriate attention to the majority of products, and to the majority of the cold chain that we need to maintain.

UNICEF has been distributing vaccines since long before the COVID 19 pandemic. Have there been any challenges in the way that the COVID-19 vaccine needs to be distributed that may not have been present in previous vaccine schemes, particularly in lower-income countries, where the necessary infrastructure or equipment may not be available? How can these issues be addressed?

UNICEF has been working with government bodies and policymakers for a long time to ensure the implementation of a suitable cold chain for immunisation programmes in general, including routine programmes and child vaccination. In terms of cold chains for routine immunisation, we have been in a fortunate position in that there has been a lot of investment in cold chain mobilisation in the last four or five years. This has meant that UNICEF, working in partnership with national governments, has been able to install fridges capable of storing vaccines in the 2°C to 8°C temperature range in more than 50,000 healthcare facilities throughout the world in the last three to four years. We now have a relatively solid infrastructure established in most countries; and that infrastructure is well prepared for managing the particular challenges associated with COVID-19.

There have been issues in terms of the vaccine releases: for the moment, in most parts of the world vaccines are being released and distributed in relatively small quantities; it is essentially a staggered approach. Here in Denmark, where I am currently located, 100,000 doses will come in per week on a rolling basis. Many of the supply chains in the countries that UNICEF is supporting have been brought up to speed, and they are able to capture those rolling and staggered supplies that are coming in and make the best use of them. UNICEF is working with the countries receiving vaccines to identify whether there are any particular gaps in distribution or delivery and to ensure that those gaps are being filled, but the larger picture is that the situation is under control.

As part of the preparedness measures for receiving vaccines through the World Health Organization’s (WHO) COVID-19 Vaccines Global Access (COVAX) Facility, recipient countries must undergo a readiness assessment, in addition to following WHO guidelines. In the initial stages of establishing preparedness in a country, it is crucial to consider what that country’s capacity is at different levels, as evaluating that capacity affords the COVAX Facility the opportunity to adjust its immunisation planning accordingly. Operatives can use the information to determine at what level of a recipient country’s system to deliver the vaccine, establishing whether it would be best to bring vaccines all the way to the end user or request the end user come to the facility where the vaccine is being stored.

In general, looking into the cold chain infrastructure in the countries where UNICEF operates, the infrastructure is now largely in place in terms of refrigeration, both at the health facility level and at the community level. There are some situations in areas which are particularly hard to reach where immunisation campaigns must be organised as outreach sessions, but this is typically part of the normal immunisation routines in those areas. In these cases, cold boxes can be used for vaccine storage. The use of these strategies by the COVAX Facility and in other COVID-19 vaccination programmes is very much on a country-by-country basis, and is very much dependent on the readiness status of each country, as well as the number of vaccines coming in at any given time.

How can procurers and suppliers ensure a degree of sustainability in medical refrigeration?

In general, much of the older refrigeration technologies – including absorption technology, gas-powered refrigeration and battery-powered fridges – have been phased out on a gradual basis over the last decade or so; and they have been replaced with more environmentally friendly fridges. Of those 50,000 fridges which have been installed over the last three to four years, approximately half are direct-drive solar refrigerators: this means that the refrigerator is equipped with a solar array which uses the sun’s energy to keep the refrigerator cold. These applications of solar technology would have been considered aspirational 10 or even five years ago, but with the global programmes which have been rolled out in recent years, this kind of technology has become mainstream and is now being rolled out at scale.

Thomas Sorensen
Senior Manager

This article is from issue 17 of Health Europa. Click here to get your free subscription today.

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