There is actually a plan to gradually offer all placebo group patients the vaccine. This will be done in small groups at a time, in order to not inform all remaining participants which group they are in. The plan is to have all placebo group participants be offered a vaccine before the end of the trial. This doesn't break the trial, because there is already a good confidence level for the efficacy results, and the side effects investigation can always use additional participants. This also enables in-patient control, where you can compare the placebo condition and the treatment condition within the same patient.