Debunked: No, the Pfizer vaccine does not contain a poisonous compound
Videos being shared on social media are alleging that the Pfizer mRNA vaccine is 99.9% graphene oxide, which is created by oxidising graphite, and is intended to kill those who receive the vaccine. These videos often claim that this is supported by a study (which has not been peer-reviewed) and confirmed by a university in Spain (which it has not). Graphene oxide is not an ingredient in the Pfizer vaccine. This allegation has been debunked by the AP.