Allergic reactions to Moderna vaccine batch cause a pause from health officials Allergic reactions to Moderna vaccine batch cause a pause from health officials California has stopped administering one batch of the Moderna vaccine after state officials say a higher-than-usual number of possible allergic reactions were reported in Southern California. SAN JOSE, Calif. - California has stopped administering one batch of the Moderna vaccine after state officials say a higher-than-usual number of possible allergic reactions were reported in Southern California. The incidents happened at a mass drive-through vaccination site at Petco Park in San Diego. The state didn't provide an exact number but said "fewer than 10 individuals required medical attention in one day."