According to Osho, you've been 'inoculated' by social and religious conditioning, so you cannot catch the 'measles' he means - the living contagion of awakening. Fixed images of Christ, Buddha, or any master act like vaccines, blocking direct recognition. Unless you unlearn these implants and meet existence freshly, even a living Christ could stand before you and you'd miss him.
Our upbringing stuffs us with ideas that block real spiritual aliveness; drop the ideas to feel it directly.