For influenza, humans may receive either inactived vaccines (e.g. common shot) or live attenuated vaccines (e.g. nasal spray).[1] I assume whether a live virus

For influenza, humans may receive either inactived vaccines (e.g. common shot) or live attenuated vaccines (e.g. nasal spray).[1] I assume whether a live virus is attenuated in research like TFA depends on the hypothesis they're testing. ? [1] https://www.cdc.gov/flu/prevent/how-fluvaccine-made.htm https://www.cdc.gov/flu/prevent/how-fluvaccine-made.htm