Bu pryderon ynghylch cynnal sefydlogrwydd brechlyn Pfizer/BioNtech y tu allan i ganolfannau brechu mewn ysbytai gan fod angen ei storio fel arfer ar minws 70 gradd canradd.
There had been concerns about maintaining the stability of the Pfizer / BioNtech vaccine outside hospital vaccination centres as it usually needs to be stored at minus 70 degrees centigrade.