Freezing DTaP Vaccine Linked to Rise in Pertussis

Using continuous data loggers, investigators at the Baylor College of Medicine in Houston found that one-quarter of 54 vaccine refrigerators in the city’s community health centers had temperatures that dipped into the freezing range, most commonly at night and on weekends.

There was a significant 76% correlation between the percentage of vaccine refrigerators in a health region experiencing prolonged freezing temperatures and that region’s rate of pertussis, the investigators reported at the annual meeting of the North American Primary Care Research Group.

The study establishes only correlation, and there are many possible confounders and explanations, acknowledged lead investigator Dr. Patrick J. McColloster, an associate professor of family medicine at the college.

“But I think though that one thing that has been neglected in looking at the pertussis outbreaks in the United States is inadvertent freezing and the instability of DTaP – back to the cold chain again,” he said, referring to the practice of ensuring that the vaccine is continuously kept at the recommended temperature.

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