The very large increase in allergies over the last thirty years is due to the great success of immunizations administered over this time period. Since immunizations have nearly eliminated life-threatening diseases such as polio, the human immune system increasingly targets other environmental substances in order to keep working properly. Allergy symptoms such as runny nose and itchy eyes result when the immune system attacks pollen that is breathed in from the air.
Which one of the following best expresses the main point of the passage above? (Points : 1)
Immunizations often have surprising side effects.
Immunizations have been very successful in eliminating life-threatening diseases.
Viruses that once caused polio now cause allergies.
The use of immunizations has led to an increase in allergies.