At the
clinic at King Open we went to, 890 kids in the 5-11 age group got vaccinated that day, according to a pdf that Marc at Cambridge Day sent me. (Still trying to find out how I could have gotten it from the city site.) Assuming that there's a total of 5,236 kids total in that age group in Cambridge (given 576 being 11% of the kids, from
this article), that means 17% of the 5-11 kids got their first shot at the clinic.