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Strengths and Weaknesses in Vaccine Cold Chain Temperature Control

Mar 16, 2016

Vaccines and viruses have made national U.S. headlines in recent months. Outbreaks of common childhood diseases like measles in California have led to swift legislative action limiting exemptions for those who do not wish they or their children to be vaccinated. A dozen other states are considering similar laws. Some states like Mississippi and West Virginia have disallowed nonmedical exemptions yielding the highest childhood vaccination rates in the U.S.

In the U.S. the Center for Disease Control’s (CDC) Vaccines for Children (VFC) program supplies over 50% of the vaccines used for children. A 2009 NIH economic analysis showed the routine U.S. childhood immunization schedule “will prevent ∼42,000 early deaths and 20 million cases of disease, with net savings of $13.5 billion in direct costs and $68.8 billion in total societal costs, respectively. The direct and societal benefit-cost ratios for routine childhood vaccination with these 9 vaccines were 3.0 and 10.1.”  Similarly, a Vaccine Alliance report titled Return On Investment From Childhood Immunization In Low- And Middle-Income Countries, 2011–20 found even greater benefit in poor countries where spending $1 on childhood vaccines can save $16 in direct medical and productivity costs and a total of $44 in the decade following vaccination.

But what happens if those vaccinated are not protected from the target diseases because the vaccine is not effective due to extreme hot or cold temperatures before administration? This is the concern of studies tracking the cold chain in the U.S. and more recently India. 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.

Ten states in India were selected for study. The supply chain includes the following sites, the site above supplying the site immediately below.

  • Government medical supply depots (n = 4)

  • State vaccine stores (n = 35)

  • Regional (subdivision of state) vaccine stores (n = 116)

  • District vaccine stores (n = 626)

  • Primary or community health centres that act as peripheral vaccine stores (n = 26,439)

Forty test boxes containing two vials of DPT (Diphtheria, Pertussis (whooping cough), and Tetanus) vaccine were prepared with temperature monitoring data loggers set to take data every thirty minutes. Each of these boxes was then stored, handled and transported exactly as if it contained routine supplies of DPT vaccine, to one of the peripheral vaccine stores that were investigated. Each box was stored for at least 1 month in a state vaccine store (if present), 1 month in a regional vaccine store (if present), 1 month in a district vaccine store and 2 weeks in a peripheral vaccine store.

Figure 1 (Left): Map of test locations for India vaccine cold chain study

Figure 2 (Right): Test boxed prepared to look like standard vaccine containers

Table 1. Test box residence duration at each site

Like the U.S., vaccines in India are to be maintained between 2°C and 8°C. Unlike previous India studies this work examined not only elevated temperature excursions, >8°C, but freezing temperatures, <0°C. A shake test was also employed to determine if the vaccine was frozen; more will be written about this in a future piece.

Researchers then distilled the data into tables to compare results in each state and for transportation between each node in the vaccine cold chain. Results are summarized in Table 2, below. Data shows between 11% and 63% of the test vaccines were subjected to freezing temperatures, <0°C. Between 13% and 88% of test vaccines were subjected to elevated temperatures, >8°C. In every case tests showed every site and transportation mode had both freezing and elevated temperature excursions.

Table 2. Out of range temperatures by storage location and transportation mode

Table 3 examines the duration of the out of range period in each state. This is important because vaccines can in some cases withstand damage during if the out of specification duration and temperature are not very great. The CDC VFC program has a method of evaluating whether vaccines that are exposed to such temperatures are to be recalled or used, for example. The India study showed in half of the states vaccines were within the recommended control range over 90% of the time. A weighted average of all states were in specification 79.1% of the time.

Test results give one pause: there were a significant number of out of specification excursions and at some locations temperatures were very high, >17°C, persisted for long periods, >10% of the test duration at a particular site, or both. What one learns from such an exercise and how it applies in the U.S. will be examined in a future piece.

Data loggers in test boxes are beneficial to understand something went wrong and the vaccine may not be effective, but they are not preventative. For those responsible to maintain vaccines in their facilities, knowing temperatures are out of range and potentially rendering the vaccines ineffective after the fact is interesting but not helpful in the short-term. In such cases those scheduled to be protected will have to wait or may never receive the protection they require. Fault-tolerant, cloud-based cellular temperature monitoring with devices such as Temperature@lert’s Cellular Edition coupled with Z-Point wireless sensor nodes can alert medical professionals before the damage is done by providing not only email or text notifications but phone calls when temperatures begin to rise. Being able to take action before vaccine effectiveness is compromised is essential to protect the most vulnerable recipients, our children.

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