TBF, what should he have done. What would Starmer have done differently?
Overall? ... I think he would have taken much more heed of medical expert advice from the outset and he would not have 'infiltrated' SAGE with the likes of Cummings ... Starmer's whole career is about the weighing up evidence himself or consulting with experts ...
If you mean at this point in time ... then I don't think he could do anything different right now.

