The duration of protection after neonatal BCG vaccination
is not well known but commonly believed to decline gradu-
ally to non-significant levels after 10–20 years. In Saudi
Arabia, the protective efficacy of neonatal BCG vaccination
against pulmonary, meningeal or disseminated TB was fol-
lowed over a 20-year period and shown to be 82% in chil-
dren younger than 15 years, 67% in the 15–24 age group,
and 20% in persons aged 25–34 years
10至20年效期
當然都要視乎流行程度，除非TB 大流行，如果唔係都唔洗打多針，正如依家唔會無端端種返牛痘一樣
