Originally Posted by Marnica
Most vaccines are Category C in pregnant women meaning there are NO SAFETY STUDIES. A few of the flu shots are Category B which means there are only animal (usually mice or rabbits) studies but no adequate studies on humans.
This isn't an accurate explanation of pregnancy categories and is kind of alarmist IMO.
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=201.57 (about halfway down... it's kind of long, but I am in favor of going straight to the source).
Category C means there is not conclusive data in humans and adverse effects shown in animals. Category B means *either* that animal studies don't show risk and there are no studies in humans, *or* that studies in animals show birth defects but studies in humans show no adverse consequences.
A *lot* of drugs (vaccines are drugs) are Category C because it is hard to get data. Who would want to participate in that trial? It would be hard to get approval to conduct such trials, let alone find people to participate. Data typically has to be gathered through retrospective studies of people who took the drug.
I am not saying do or don't take a Category C drug, but I think it's important to understand that so many drugs are designated as Category C because of a lack of data, and this is in large part simply an artifact of the fact that it's hard to conduct studies on pregnant women compared to other populations. This is by no means limited to vaccines.