Yes. When you change the dosing like that, it means that you ask the people to take medication, or a vaccine in this case, in a different posology. You have to assess the risk and the benefit in these cases.
When you give that to a patient, you have to inform them in detail of what will be the benefit for their health, and also the potential risk. In this case, we cannot really give them this information, because we don't have the data for that.