This is the new meningitis vaccine and requires 2 doses at least 30 days apart. The PTR said it was recommended, but not required - but may be mandated upon arrival (waiting on a CDC recommendation). I know a 1/2 dozen kids that have received it, and every one has complained of very sore arms lasting 3 to 5 days after each round. A couple had mild reactions (flu-like symptoms for 24-48 hours). I have heard from some that in some locations the Bexsero vaccine is in short supply, so may not be an option, but based on the limited sample size I am aware - I would recommend getting the first dose prior to I Day. (DD was able to complete both rounds) Not a doctor, but Plebe Summer is enough of a hassle without a sore arm and though if sick will be well cared for - it's a lot better to be home sick than in Mother B.