Pfizer is working out some kinks in the first week of its coronavirus vaccine release.
U.S. health officials told reporters yesterday some of the shots are being kept too cold.
They're supposed to be stored at minus 70 degrees Celsius.
But some vaccine doses delivered to California had to be replaced after the storage temperatures dipped to minus 80.
Vaccine makers are trying to figure out whether the colder temperatures affect the safety or efficacy of the vaccine.
Pfizer is also reportedly running into manufacturing limitations and has asked the U.S. government for help.