Vaccine Storage and Handling Studies at NIST Michal Chojnacky National Institute of Standards and Technology Sensor Science Division, Themodynamic Metrology Group Gaithersburg, MD michalc@nist.gov http://www.nist.gov/pml/div685/grp01/vaccines.cfm Project funded by the Centers for Disease Control and Prevention CDC Contacts: Patricia Beckenhaupt, Public Health Analyst
Overview In 2009, CDC approached NIST to investigate vaccine storage and temperature monitoring issues in the VFC program NIST evaluated CDC/VFC cold-chain management practices in a series of studies designed to replicate everyday conditions in vaccine provider offices Phase 1: Refrigerator study Household, consumer grade refrigerators originally designed for food storage 1. Stand-alone refrigerator (freezerless) 2. Dual-zone (combination, swinging door unit with freezer on top) 3. Dormitory-style Pharmaceutical grade, purpose-built refrigerators for storing vaccine and biologics 1. Full-size pharmaceutical refrigerator 2. Small (under-the counter) pharmaceutical refrigerator Suitability for vaccine storage and impact of operating conditions on performance Phase 2: Data logger evaluation Evaluate of out-of-box performance and manufacturer-specified accuracy over 0 C to 10 C Track stability over 19 months to assess possible measurement drift Determine proper use so that measurements reflect stored vaccine temperatures
Phase 1: Refrigerator Evaluation Method and Test Criteria 5 refrigerator styles Thermal mapping of each unit Varied loading patterns: density & packaging material Normal use simulation: open/close door Variable room temperature Power outage & recovery
Results: Temperature Stability of Refrigerators top wall back of tray, near wall near cooling unit data collected over 26 day period 45 days top wall 51 days 49 days
Dormitory-style units should NEVER be used for vaccine storage In the NIST vaccine refrigerator study, the dormitory-style unit exhibited severe temperature control and stability issues. Within 2 weeks of use, the refrigerator set point had drifted approximately 5 C colder, freezing the vaccines contained inside. The unit also exhibits large spatial temperature gradients. There is no good vaccine storage area inside a dorm-style unit. Dorm-style refrigerators should NOT be used for vaccine storage under any circumstance!
Dual Zone Case Study: Does freezer setting affect refrigerator performance? Sensors arranged throughout freezer and refrigerator compartments Varied freezer set point dial, refrigerator temp setting left unchanged 50%, 75%, and 100% (maximum cold setting) Recorded temperature effects in both compartments Results: change in refrigerator sensor temperatures ~10% temperature drop recorded by freezer sensors In order to change the refrigerator compartment temperature by 1 C, the freezer compartment must be adjusted by 10 C In our test unit, adjusting the freezer temperature is unlikely to negatively impact vaccines stored in refrigerator compartment -9 Freezer sensor temperatures 1F (top back wall) 10 Refrigerator sensor temperatures 11R (floor) -10 2F (low back wall) 9 12R (vial - tray) Average temperature, C -11-12 -13-14 -15-16 -17 3F (vial - in tray) 4F (ceiling) 5F (floor) 6F (vial - in box) 7F (glycol - in tray) 8F (mid right wall) 9F (air - top) Average temperature, C 8 7 6 5 4 3 2 13R (air - mid) 14R (lower left wall) 15R (lower right wall) 17R (glycol - in tray, top) 18R (glycol - mid) 19R (glycol - in tray, low) 20R (inside syringe box) LA_R (low, in tray) -18 10F (glycol - top shelf) 1 LD_R (glycol - in tray, top) -19 50% 75% 100% Freezer temperature dial setting (% of max cold) LC_F (top shelf) LE2 _F (glycol - in tray) 0 50% 75% 100% Freezer temperature dial setting (% of max cold) LE1_R (glycol - low) LF_R (vaccine box - in tray)
Dual Zone Case Study: Is this refrigerator model suitable for frozen vaccine storage? Temperature, C 20 15 10 5 0-5 -10-15 -20-25 -30 Coldest Freezer Setting 17:00 18:12 19:24 20:36 21:48 23:00 0:12 Time, h:min 1F (top back wall) 2F (low back wall) 3F (vial - in tray) 4F (ceiling) 5F (floor) 6F (vial - in box) 7F (glycol - in tray) 8F (mid right wall) 9F (air - top) 10F (glycol - top shelf) 11R (floor) 12R (vial - tray) 13R (air - mid) 14R (lower left wall) 15R (lower right wall) 17R (glycol - in tray, top) 18R (glycol - mid) 19R (glycol - in tray, low) 20R (inside syringe box) LA_R (low, in tray) LC_F (top shelf) LD_R (glycol - in tray, top) LE1_R (glycol - low) LE2 _F (glycol - in tray) LF_R (vaccine box - in tray) Freezer thermostat dial set to midpoint position: vaccine vial temperatures between -13 C and -11 C Upper temperature limit for frozen vaccine storage = -15 C Maximum cold setting: vial temperatures fluctuate between -19 C and -13 C Upper limit exceeded 5 C fluctuation due to freezer control is large no room for set point error Defrost cycle temperature spike 2+ hr thermal excursion > -15 C, every 24 hrs Possible significant impact on vaccine quality
What kind of refrigerator should I use? Household, consumer-grade units Pharmaceutical, purpose-built units Stand-alone Dual-zone Under-the-counter Full-sized Dual-zone unit is acceptable for refrigerated vaccine storage only do not use freezer compartment
Vaccine Storage Methods and Locations DUAL-ZONE NO vials touching glass shelf or directly under cooling vent = 2 to 5 C colder PHARMACEUTICAL STAND-ALONE Avoid storage on top shelf near cooling vent. First location to exceed max allowed temp during outages. No storage in crisper drawers: thermally isolated + floor level runs cold. Remove drawers, fill space with water bottles Manufacturer recommends no floor storage, but vial TC maintained at 2 to 8 C throughout testing 1 to 2 C colder than main fridge space Best storage practice place vaccines in center fridge space, contained in original packaging, inside designated storage trays positioned 2 to 3 in from refrigerator walls
Phase 2: Temperature Monitoring How do you know if stored vaccines are safe and effective? Track temperature history Refrigerator temperature is NOT a single point measurement Refrigeration cycle compressor timing Air circulation patterns spatial temperature variations Use patterns door opening, loading density, temperature set point Environmental conditions room temperature variation, power failures Defrost cycle Thermometer location what are you measuring? A refrigerator is ONLY as good as the temperature monitoring system inside High-tech, pharmaceutical-grade units are still affected by variable conditions Accurate temperature history that reflects actual vaccine temperatures is imperative to effective vaccine management