Graphic-output temperature data loggers for monitoring vaccine refrigeration: implications for pertussis.

We conducted the first US study using graphic-output temperature data loggers in quantifying cold chain failure. Fifty-four vaccine refrigerators of a county outpatient health system were studied. Forty-eight percent maintained temperatures of 2°C to 8°C and 24% had protracted periods of temperatures less than 0°C. The correlation between the percentage of refrigerators with freezing temperatures and the pertussis rate for each health region was r = 0.76. The findings suggest that improper vaccine storage may have contributed to recent increases in pertussis rates.