Open talk about negative features of COVID-19 vaccines increases trust Concerns have been raised about the AstraZeneca and Johnson & Johnson vaccines regarding very rare but potentially fatal side effects related to low blood platelet counts and blood clots. Recently, reports also emerged that the Pfizer-BioNTech vaccine may cause a rare yet serious side effect: heart inflammation. Concerns about side effects may trigger vaccine hesitancy, which the WHO considers one of 'Ten threats to global health'. Securing sufficient acceptance of vaccines is a key challenge in defeating the coronavirus p...