What type of vaccine is not suitable for pregnant women?

Live attenuated vaccines are not suitable for pregnant women because they contain live organisms that are weakened but still capable of replication. The concern with live attenuated vaccines during pregnancy is that there is a theoretical risk of the vaccine strain causing disease in the fetus, as the immune system of a pregnant woman is altered, making it challenging to ensure complete safety. In contrast, inactivated vaccines contain killed pathogens and are generally considered safe for use during pregnancy since they do not carry a risk of causing disease in either the mother or the fetus. Similarly, subunit vaccines, which consist of only parts of the pathogen, also do not pose a risk of live infection and are typically safe for pregnant women. Therefore, live attenuated vaccines are the specific type that should be avoided during pregnancy.