Tools and approaches to ensure quality of vaccines throughout the cold chain

Abstract

The Expanded Program on Immunization was designed 40 years ago for two types of vaccines: those that are heat stable but freeze sensitive and those that are stable to freezing but heat labile. A cold chain was developed for transport and storage of such vaccines and established in all countries, despite limited access to resources and electricity in the poorest areas. However, cold chain problems occur in all countries. Recent changes to vaccines and vaccine handling include development and introduction of new vaccines with a wide range of characteristics, improvement of heat stability of several basic vaccines, observation of vaccine freezing as a real threat, development of regulatory pathways for both vaccine development and the supply chain, and emergence of new temperature monitoring devices that can pinpoint and avoid problems. With such tools, public health groups have now encouraged development of vaccines labeled for use in flexible cold chains and these tools should be considered for future systems.

Keywords::

• cold chain
• cool water pack
• supply chain
• temperature monitoring device
• temperature sensitivity
• vaccine development
• vaccine freezing
• vaccine vial monitor

Acknowledgements

Authors would like to thank Ted Prusik (Temptime Corp.) for his review before the article was submitted.

Financial & competing interests disclosure

U Kartoglu is a scientist working for WHO at the Department of Essential Medicines and Health Products responsible for Global Learning Opportunities, a training network. J Milstien is an independent consultant. J Milstien has done consultancy work with Temptime Corp., which produces time and temperature indictors; however, amount received for this work is insignificant. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• In the past almost 40 years, Expanded Program on Immunization (EPI) has been one of the most successful and cost-effective interventions known in terms of saving the lives of infants and their mothers. This progress has been made despite the fact that most vaccines need some kind of cold chain, and about one-fourth of the global population still has no access to electricity and four-fifths of these live in rural areas of South Asia and sub-Saharan Africa.

• The EPI vaccine delivery system has been based on vaccines that fall into two categories: those that are heat sensitive but stable to freezing and those that are stable for days at temperatures up to 40°C but sensitive to freezing. But newer vaccines numbering >30 have a wide range of temperature stability and sensitivity characteristics.

• One approach of improving the integrity of the vaccine delivery system is to remove the obstacles in maintaining a refrigerated supply chain, which can be approached by a combination of three methods: developing ways to prevent vaccine freezing, for example, by using cold water packs instead of ice for transport; using more effective time–temperature monitors that can go on every vial of vaccine from the time it leaves the manufacturer until it reaches the recipient; and by better control and regulation of the supply chain.

• A second approach is by using vaccines with improved stability to temperature variations and making this information widely known, which requires collaborations with vaccine manufacturers and regulators.

• Vaccines are now more heat stable than they were originally and some can now be safely used in a controlled temperature chain, with a relaxation of the strict 2–8°C standard previously used.

• Optimal immunization programs depend on a mix of stable vaccines used optimally in accordance with their stability, fitted with appropriate temperature monitoring devices on each vial, and by assessing the potential threat of temperature excursions using a risk management approach.

Notes