Live attenuated vaccines
What it means
Weakened whole organism → strong, durable immunity, often from one/two doses. UK examples: MMR, varicella-zoster, BCG, rotavirus, intranasal flu (children), yellow fever, oral typhoid.
Worked example
Contraindicated in significant immunosuppression and pregnancy (e.g. HIV with low CD4, high-dose steroids, biologics, chemotherapy) — risk of disseminated infection from the vaccine strain.
In the exam
A child due a vaccine is on high-dose immunosuppression; the team must avoid a vaccine containing weakened live organisms because of disseminated-infection risk.
What settles it
Only LIVE vaccines are contraindicated in immunosuppression/pregnancy; inactivated/subunit/mRNA vaccines are safe (may be less effective).
Classically confused with
Inactivated / subunit / mRNA vaccines
Source: Green Book (UKHSA)