Not yet investigated
What we have so far
It is not one number — it depends on R0, on mixing, and on whether the vaccine blocks transmission or only disease. Measles needs about 95%; most things need far less.
This star is on the map because the show intends to take the question apart properly — the trials, how it is actually tested, whether the thing sold is the thing studied. That work is not done yet, and nothing here should be read as a conclusion. When the investigation is published it will appear on this page.