I just heard that the pertussis vaccine is not actually very effective - on 70 percent, at best. So now I am wondering whether to give the pertussis vaccine at all? I know that vaccines can have some nasty side effects. My daughter is six months. Is pertussis still dangerous at that age? I didn't think so, that is why I am asking. What are the side effects of the pertussis vaccine, and what do you advise I do?