Huh, that's nonsense. Every vaccination also carries risks, so there can be no moral obligation if the risks outweigh the benefits. That said, I also disagree with the moral obligation. At the very least, there are also other scenarios to consider. For example if only a small group is at risk and can't be vaccinated (too risky), that small group could be isolated or choose to self isolate. Afaik it already happens with chemotherapy patients who are being isolated. There is no obligation for the rest of the world to disinfect everything and walk around in hazmat suits so that chemotherapy patients can walk freely in the outer world.