If EN is high and Vin>Vout, the output voltage will follow the input voltage minus a diode drop. The diode is internal to the MAX17222.
For example, if a Vout of 4.2V is chosen and a Vin is normally at 3V but if for any reason for a moment (e.g. 30secs) Vin goes to 5V with a load of about 20mA, the output voltage will be (5V-VD) which will be around 4.3V.
However if EN is low and you are using a part which has the true shutdown feature (such as those in the MAX1722X family) then the Vout will be floating regardless of the Vin value.