الفهرس 
Introduction
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Abstract
In 1963, a killed measles vaccine was licensed in USA, but it was not accepted, so another 2 live attenuated vaccines was produced which are Schwartz vaccine, Moraten vaccine which are used now all over the world. A live attenuated mumps vaccine (Jeryl Lynn) was produced, its protection in 97%. A three rubella vaccine were produced, but a fourth one was licensed and is used now in USA and Egypt which RA27/3. Also, a triple vaccine was licensed (MMR) measles, mumps, rubella vaccine. Because no vaccine is effective 100%, so a percentage of vaccine failure was reported, and this vaccine failure is classified into 2 categories. 1?1ry. Failure, which is failure of the vaccine produced antibodies, which is due to 2 causes: a)?Giving killed vaccine or error in handling the vaccine. Or b) No response to the vaccine due to either : 1)?Giving vaccine during infection, so interferon suppress it. Or 2) Giving vaccine while antibodies are present. 2?2ry. Failure, due to that the antibodies produced is decreased with time till disappearing.