Do basophil activation tests help elucidate allergic reactions to the ingredients in COVID‐19 vaccines?

The worldwide use of COVID‐19 vaccines has shown that immediate allergic reactions to the ingredients are rare but should be clarified by means of an allergological work‐up. This review aims to highlight the current state of knowledge and possible pathogenesis based on the literature published to date. In addition to recording a detailed history and performing skin tests, cellular tests (basophil activation or basophil histamine release test) by using the vaccines or modified compounds containing polyethylene glycol (PEG), rather than unmodified PEGs, have proven to be particularly helpful. Negative results with vaccines seem to indicate tolerance. Details of the performance of these cellular tests with different vaccines, PEGs of different molecular weights, other ingredients of the vaccines, as well as other PEGylated drugs, and the results in the context of COVID‐19 vaccination of various working groups worldwide are summarized.