I would go check to see who's the head of the Health Policy unit at the WHO before saying who has more connections at the WHO
Just a hint, he's from Michigan
Yes, Yale does have WHO connections, but you'll see that more than enough Michigan SPH students do their summer internships with the WHO. In terms of the Health Policy side at Michigan, they have faculty members who were integral in the creation of the UN Millenium Project and others who have gone to work with SEVA and Google.org (Google's Philanthropic arm...actually headed by Larry Brilliant, a UMich SPH grad)
UMich does have the largest and oldest alumni society for PH in the country, which a strong base for employment and internships. 100% of students in the HMP program at Michigan are employed at graduation...the demand is great for Michigan students...I heard that there are companies and hospitals each year that ask for UMich grads but can't seem to get them...
There is a reason for UMich being #1 HMP program in the country since 1994, it's because of the alumni. I'm assuming that you have the alumni brochure from the interview day...just look down that list and do a quick search on these people...UMich has been proven to produce some of the most influential people in healthcare management and policy today..
Yale is a great school, health policy should be noted as a strength in the program due to the colaborations they should have with their Public Policy departments. They do have strong connections to the WHO and UN...but that seems to be the case for any Top PH school in the country, it's hard to say who has more connections really..But you'll get a good education at Yale if you decide to attend there.
You should look around the forum a bit more, I know a lot of us have had conversations about these two schools in specific detail. So good luck on your decision.