Public health relies on trust. Advertising relies on twisting the truth, even deceiving people, to persuade them to buy a product they may not need. Trust is maintained by telling the truth, giving others accurate information and sound advice. If inclined, you can change direction, trading on trust that you have built in order to deceive more effectively. This works until the audience starts to understand that you have started lying. It is the worst sort of deceit. The World Health Organization (WHO) has adopted this latter course, using its former status to deceive the public in order to increase global uptake of COVID-19 vaccines.