I don't think your analogy is right. A vaccine has a small risk that it can cause harmful effects to a small subset of the population. The predicted outcome is

I don't think your analogy is right. A vaccine has a small risk that it can cause harmful effects to a small subset of the population. The predicted outcome is very positive. Societal collapse and power vacuums in Iran and neighboring countries have a high risk of resulting in harm to a large population. The risk is very high and it has happened before -- in the same country, even! Collapse and revolutions, unlike vaccines, are a high risk gamble. They can, for example, result in the Islamic Revolution, ISIS or who knows what. So I don't think the analogy works at all.