How come some antibodies that our immune system produces, dons last a lifetime?

Question

Some can last a lifetime (tetanus), some last just a small period. Wouldn't it be better if they were around in our body forever?

Answer 1

all antibodies last forever, thats why when you get sick, you get infected by a viral disease ONCE. however, if you are referring to colds, lemme tell you, colds are caused by MANY viruses and bacteria, thus, the previous virus that infected you cannot again but when you get colds again, its a totally different virus with the same infection =]