Healthcare Providers Use ‘Shake Test’ To Test Efficacy of Vaccines

Vaccine safety and efficacy is a worldwide concern. Parents and patients alike desire to protect themselves and their children from debilitating and deadly diseases. Vaccines are considered by those in developed and developing countries alike to be truly miracle drugs.

Yet aside from their safety and efficacy as described by regulatory testing, healthcare providers understand that the vaccine they receive and administer may be compromised if not handled and stored properly, as displayed in China recently. Like many foods, vaccines need to be maintained within a tightly designated temperature range to ensure their quality and effectiveness. Many vaccines are refrigerated at temperatures specified as between 2°C and 8°C. Frozen vaccines are to be maintained at temperatures of -15°C or lower. So how do healthcare providers know if the vaccines they administer have been refrigerated properly?

A 2013 World Health Organization (WHO) Bulletin titled “Frequent exposure to suboptimal temperatures in vaccine cold-chain system in India: results of temperature monitoring in 10 states” looked at the five-level supply chain for India’s Universal Immunization Programme that serves 27 million infants and 30 million pregnant women each year. Results showed that many vaccine samples were exposed to temperatures outside of specified ranges, potentially damaging the vaccine’s effectiveness.

Certainly there are lessons to learn about vaccine storage and transport. The focus here is the simple yet effective Shake Test employed to determine whether or not vaccines have been compromised by freezing.

The shake test has been used for years by health care providers and their suppliers since the 1980s. This method was developed from empirical field observations by healthcare professionals. Study authors note the shake test’s description was available nowhere except on a poster in the archives of the World Health Organization (WHO). Although the shake test is widely practiced in the field by staff at all levels of the health system, it has never been validated as a reference test by comparison to a “gold standard”.  In 2010, testing the validity of the shake test for detecting freeze damage to vaccines was examined by a study commissioned by the WHO and supported by DHL in partnership with UNICEF, and a host of pharmaceutical companies. Two links to the study results are U.S. NIH Study Link and WHO Bulletin Link.

The study begins by noting, liquid formulations of aluminium-based vaccines against diphtheria, pertussis, tetanus, hepatitis B and Haemophilus influenzae type b, alone or in combination (adsorbed vaccines), should not be frozen. When a vaccine is damaged by freezing, the potency lost can never be restored – the damage is permanent. Freeze-damaged vaccines have lower immunogenicity and are more likely to cause local reactions, such as sterile abscesses.

Authors found the most recent systematic literature review of vaccine freezing practices showed that accidental freezing occurs across all parts of the cold chain. Between 14% and 35% of refrigerators or transport shipments were found to have exposed vaccines to freezing temperatures, while in studies that examined all segments of the distribution chain, between 75% and 100% of the vaccine shipments were exposed. More rigorous study designs were associated with higher levels of exposure to freezing.

So how do providers know vaccines have been frozen, especially when there are so many opportunities in the cold chain? One way is the systematic study described in the India study above. Indeed, modern temperature monitoring technology has made tracking temperature histories easier. Small, wireless, battery powered sensors can be placed with temperature sensitive medications from source to end user and provide a detailed temperature profile health providers can review before they administer the medication.

However, since the industry is a long way from implementing such a plan, and there is a cost both in terms of hardware and professional review of the data, the Shake Test is a simple, yet effective method to determine the efficacy of a vaccine.

The study’s authors put together a protocol to provide validation for the shake test, or to disprove its effectiveness as a useful tool. We’ll explore the Shake Test method and findings in greater detail in our next piece.