Introduction
Vaccination against influenza has the potential to substantially reduce mortality and morbidity
both through direct protection (reduced risk of infection in those receiving the vaccine) and
through indirect protection (reduced risk of infection in those not receiving the vaccine) [1,2].
Because children have a high burden of influenza-related illness and make a large contribution
to influenza transmission in the wider community, it has been proposed that preferentially vaccinating
this age group would represent efficient use of vaccine in high-income countries in the
temperate climate zone [3–7]. The experience in Japan, where children were routinely immunized
against influenza between 1962 and 1987, suggests that indirect benefits could be large
[8]. Moreover, in settings where access to health care is limited, or where voluntary uptake of
influenza vaccination in high-risk populations has been low, vaccinating school-aged children
could represent a pragmatic and effective intervention to reduce influenza morbidity and mortality
in the whole community. A further advantage of targeting this age group is that vaccine
effectiveness may be greater in children than in elderly high-risk age groups [3]. Such a policy
may be particularly relevant for Thailand, where despite free provision of seasonal influenza
vaccine to all Thai nationals aged 65 y and above since 2008, annual vaccine coverage in this
age group has remained in the region of 10% [9].