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Is freezing in the vaccine cold chain an ongoing issue? A literature review

Friday, 31st of March 2017

Excerpt below; full text is at http://www.sciencedirect.com/science/article/pii/S0264410X16309471

Vaccine

Volume 35, Issue 17, 19 April 2017, Pages 2127–2133

Review

Is freezing in the vaccine cold chain an ongoing issue? A literature review ^☆

Celina M. Hanson^,,
Anupa M. George,
Adama Sawadogo,
Benjamin Schreiber
United Nations Children´s Fund (UNICEF), NY, NY, USA

Available online 30 March 2017

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http://dx.doi.org/10.1016/j.vaccine.2016.09.070

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Under a Creative Commons license

Open Access

Abstract

Vaccine exposure to temperatures below recommended ranges in the cold chain may decrease vaccine potency of freeze-sensitive vaccines leading to a loss of vaccine investments and potentially places children at risk of contracting vaccine preventable illnesses.

This literature review is an update to one previously published in 2007 (Matthias et al., 2007), analyzing the prevalence of vaccine exposure to temperatures below recommendations throughout various segments of the cold chain. Overall, 45 studies included in this review assess temperature monitoring, of which 29 specifically assess ´too cold´ temperatures. The storage segments alone were evaluated in 41 articles, 15 articles examined the transport segment and 4 studied outreach sessions. The sample size of the studies varied, ranging from one to 103 shipments and from three to 440 storage units. Among reviewed articles, the percentage of vaccine exposure to temperatures below recommended ranges during storage was 33% in wealthier countries and 37.1% in lower income countries. Vaccine exposure to temperatures below recommended ranges occurred during shipments in 38% of studies from higher income countries and 19.3% in lower income countries.

This review highlights continuing issues of vaccine exposure to temperatures below recommended ranges during various segments of the cold chain. Studies monitoring the number of events vaccines are exposed to ´too cold´ temperatures as well as the duration of these events are needed. Many reviewed studies emphasize the lack of knowledge of health workers regarding freeze damage of vaccines and how this has an effect on temperature monitoring. It is important to address this issue by educating vaccinators and cold chain staff to improve temperature maintenance and supply chain management, which will facilitate the distribution of potent vaccines to children.

1. Introduction

Immunizations are hailed as one of the most important public health interventions known saving millions of lives every year. Vaccines are responsible for the eradication of smallpox and the global community is currently working towards the eradication of polio. To reach current disease elimination and eradication targets, high immunization coverage rates are required. A well-functioning cold chain is at the center of ensuring potent vaccines reach their intended population in an equitable and timely manner [2] ; [3].

Vaccines are biological products that slowly become inactive over time and must be kept within narrow temperature ranges from manufacturers to those receiving them [3]. When exposed to temperatures outside of this narrow range, the loss of potency may be accelerated [4]. Before 2007, attention had been focused on examining the effects of vaccine exposure to heat. However, exposure to freezing temperatures are equally damaging to the quality of many vaccines as the process renders them inactive [4]. When exposed to freezing temperatures, the adjuvants contained in some vaccines clump together adversely affecting the immunological properties of these vaccines [4]. Thus, the World Health Organization (WHO) recommends the following vaccines be stored and transported at 0–10 °C: Diptheria-tetanus containing vaccines, tetanus toxoid (TT), hepatitis A and B, human papillomavirus (HPV), meningitis C, pneumococcal (PCV), cholera, influenza, haemophilus influenza b (Hib), typhoid and inactivated poliovirus (IPV) [4]. In 2015, approximately 59% of vaccines procured from the United Nations Children´s Fund (UNICEF) Supply Division´s (SD) catalogue are freeze-sensitive [5]. Furthermore, the number of freeze-sensitive vaccines recommended by the WHO has increased by 50% over the last ten years [4] ; [6].

In 2007, a review of studies examining temperatures in the vaccine cold chain from 1985 to 2006 reported that in all segments of distribution, vaccines in 75–100% of monitored vaccine shipments had been exposed to freezing temperatures [1]. This 2007 review seems to have raised awareness about the risks of vaccine exposure to freezing temperatures in both developed and developing countries of varying climates.

The objective of this updated review is to examine the results of more recent monitoring studies regarding freezing temperatures within the immunization supply chain.