Proper Vaccine Storage May Help Curb Rising Incidence of Pertussis and Other Vaccine-Preventable Diseases

Improper vaccine storage is surprisingly common and may be one cause of the rising incidence of vaccine-preventable diseases across the United States.

A systematic literature review focused on the risk of improper freezing of vaccines and strategies to improve vaccine storage across the supply chain.

The review, conducted by Dipka M. Matthias and colleagues with support from the Bill & Melinda Gates Foundation and the Bureau for Global Health, identified a total of 35 articles related to cold chain conditions. Of these studies, 18 were conducted in undeveloped countries. The remaining 17 studies were conducted in developed countries, including 7 studies from Australia.

In developed countries, 16.7% of vaccines were found to be stored at below-freezing temperatures at some point in transport. Similarly, during storage, 13.5% of refrigerators registered temperatures below the freezing-point threshold.

Temperature controls were even worse in less developed countries, where 35.3% of vaccines were transported at below-freezing temperatures. Additionally, more than one-fifth (21.9%) of refrigerators in less developed countries exposed vaccines to sub-freezing conditions.

Based on this study, the risk for loss of vaccine potency is substantial and may reduce the benefits of such vaccines for patients. To combat improper freezing throughout the supply chain, investigators recommend several strategies, including using cool water packs instead of frozen ice packs during the transport of freeze-sensitive products, using electronic temperature monitoring, and updating policies and training related to the storage of vaccines.

Critics of the above study may argue that minor variations in storage temperature may not always lead to reduced vaccine efficacy. Although it is true that established algorithms are in place to determine whether or not a temperature excursion necessitates disposal of a vaccine, some evidence shows a relationship between improper storage and patient harm.

In a 2011 study published in the American Journal of Public Health, Patrick McColloster, MD, and Carlos Vallbona, MD, both of the Baylor College of Medicine in Houston, Texas, found that improper cold chain conditions correlated with higher rates of vaccine-preventable disease in Harris County, Texas where the annual incidence of pertussis nearly tripled between 2001 and 2005.

To determine whether the rise in pertussis incidence could be linked with improper vaccine storage, investigators installed digital data loggers in a total of 54 refrigerators at 13 community health centers across Harris County. Nearly one-fourth (24%) of refrigerators registered freezing temperatures at least once during temperature logging, and fewer than half (48%) of refrigerators registered in-range temperatures at all times.

Using the Pearson correlation statistic, investigators found a statistically significant relationship between higher-than-average pertussis incidence rates in regions served by centers with refrigerators that did not maintain stable temperatures (r = 0.76; P <.05). These results show that use of digital data loggers with a graphical output may help curb growth in the incidence of pertussis, and potentially other vaccine-preventable diseases through improved vaccine storage conditions.

Considering the correlation between improper vaccine storage and rising pertussis incidence, the importance of proper vaccine storage is an important public health priority. Taking simple precautions such as using a relatively inexpensive graphical temperature logger in refrigerators and using proper cooling packs during transit may help protect expensive vaccines from heat damage and low-temperature damage, which may subsequently protect more patients from vaccine-preventable diseases.

References:

• Matthias DM, Robertson J, Garrison MM, Newland S, Nelson C. Freezing temperatures in the vaccine cold chain: a systematic literature review. Vaccine. 2007;25(20):3980-3986.
• McColloster P, Vallbona C. Graphic-output temperature data loggers for monitoring vaccine refrigeration: implications for pertussis. Am J Public Health. 2011;101(1):46-47.