My granddaughter had an allergic reaction to the whooping cough vaccine at 4 months old. Her little brain swelled to the point it made her left eye cross. Poor thing spent 5 days in pediatric intensive care with vomiting and fever. Baby then had to wear at patch on right eye to make left eye straighten out for six weeks. Doctors said the reaction was rare and not to give her another whooping cough vaccine. They could not tell us if brain damage was done till she reached 18 months. Thank God this was not the case. Gabi has above intelligence she is now in the second grade and reads on a fifth grade level. The Doctors were concerned of possible brain damage due to the swelling not the vaccine, but the vision in her left eye is weaker than the right and she may need glasses in the future.