Several thousand doses of Pfizer's COVID-19 vaccine were quarantined in California and Alabama after the US authorities encountered a transit anomaly that caused the storage temperature to get too cold.

According to Gen. Gustave Perna, the one overseeing the logistics for Operation Warp Speed, the doses never left the truck, but they have to ensure that this anomaly is safe.

Transit Anomaly Caused the Sudden Drop of Temperature

The COVID-19 vaccine that Pfizer developed with the German drugmaker BioNTech needs to be stored at a temperature of minus 70 degrees Celsius. The CDC said that the vials were stored in trays in which each tray carries a minimum of 975 doses.

Gen. Perna told the reporters that they had to send back two trays of Pfizer's vaccines that arrived in two different locations in California because the storage temperature got colder than it should be, CNBC reported.

"We returned them immediately back to Pfizer and we sent immediate shipments to replace those two trays. We're working with the FDA now, CDC, FDA, and Pfizer to determine if that anomaly is safe or not, but we're taking no chances and we can see that," Gen. Perna said.

However, the anomaly happened again in Alabama when two trays that were delivered in one location also went to minus 92 degrees. But they were able to stop and quarantine the vaccine and get a replacement shipment to Alabama, he said.

Authorities said that it is still unclear what caused the transit anomaly that led to the sudden drop of storage temperature of Pfizer's COVID-19 vaccine. As of now, Pfizer has not yet released a comment regarding the issue.

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Logistical challenge

The unique storage requirements of Pfizer's COVID-19 vaccine poses a great challenge, said Kurt Seetoo, the immunization program manager at the Maryland Department of Public Health in Baltimore. This is especially true when delivering the vaccines to other locations, such as in other countries.

Tinglong Dai, a medical logistics specialist at Johns Hopkins University, said that changing the storage requirements would make it easier to deliver Pfizer's COVID-19 vaccines. The CDC warned against buying specialized freezers in its current "vaccine playbook."

To help this dilemma in logistics, Pfizer has developed a shipping container that can maintain a temperature of minus 70 degrees Celsius, the required temperature for the vaccine, for up to ten days unopened. Although it could last for 30 days with a regular refill of dry ice, according to an article by Fortune.

However, Dai said that every time dry ice is added, it could be an opportunity of making mistakes. Pfizer has announced that it is currently working on a durable version of the vaccine that is "lyophilized," or freeze-dried, according to the news outlet.

Americans have started receiving the vaccine on Monday upon the approval of the FDA last Friday. The officials and authorities have said that it is likely that they will be facing brand new logistical challenges as the vaccine is required to be stored at an ultracold temperature.

READ MORE: COVID-19 Vaccines Are On Its Way to the US: Here's What You Need To Know

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