It is lame wording in this instance.
"all the current evidence indicates polio vaccines do not cause chicken pox" is fine. They are not ruling it out, but they see no evidence for it. Acceptable science-speak.
"all the current evidence indicates polio vaccines are free of SV40" is pretty lame. Either it contains SV40, or it doesn't. If they can't tell, i am not impressed. They should know the ingredients in vaccines.