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Davies states (1) that BCG is “not a very effective vaccine” because a
immunisation gave “only 75% protection … for a maximum of only 15 years”.
This deliberately pessimistic interpretation (“it protected only three out
four children”) is often trotted-out in discussions of BCG, without
to other established vaccines. For example, the Green Book (2) notes that
typhoid vaccine has an efficacy of 55-75%, oral typhoid vaccine “of about
to 60%” (both must be boosted every three years); influenza vaccines “70
80% protection” against well matched influenza virus strains (less in the
elderly) for only one year; a single MMR confers 61% to 91% protection
mumps, etc. Classical inactivated vaccines require multi-dose schedules
and childhood boosters to achieve 80-90% levels of protection. Whether BCG
should be used in a general or targeted manner in the UK is open to
discussion, but whether an efficacy of 75% that lasts a decade and a half
a single shot is “effective”, when placed in comparison with other