We compared seven vaccination policies against a baseline policy (policy 0) of no additional
vaccination (Table 1). Policies 1–6 involved annual vaccination of children in specified age
ranges: 2–11 y for policies 1 and 2, and 2–17 y, 2–5 y, 6–11 y, and 12–17 y, respectively, for polices
3–6. In policies 2–6, children were vaccinated with LAIV. Policy 1 differed from policy 2
only in the use of TIV instead of LAIV. Age groups were chosen to reflect the three stages in
the Thai education system (3–5 y, kindergarten; 6–11 y, elementary school; 12–17 y, secondary
school). For the youngest age group we extended the age range to 2 y, the minimum age at
which LAIV can be used. For comparison we also considered a policy of expanding annual coverage
levels with TIV to 66% in those aged at least 60 y (policy 7). In all other scenarios (including
policy 0), 10% of those aged 60 y and over were assumed to receive TIV annually. For a
given value of willingness to pay per disability-adjusted life year (DALY) averted (the cost-effectiveness
threshold), we consider the optimal policy to be the one with the highest expected
incremental net benefit (INB). The INB is the difference between the monetary value of health
gains (the product of the number of DALYs averted by the policy and the cost-effectiveness
threshold) and the costs of these health gains.
We evaluated the sensitivity of our results to alternative assumptions about (i) mixing patterns
between age groups, (ii) vaccine effectiveness, (iii) baseline immunity (prior to vaccination),
(iv) vaccine coverage, (v) influenza transmissibility in Thailand, (vi) vaccine costs, and
(vii) the probability that an influenza infection is symptomatic (Table 2).
We compared seven vaccination policies against a baseline policy (policy 0) of no additionalvaccination (Table 1). Policies 1–6 involved annual vaccination of children in specified ageranges: 2–11 y for policies 1 and 2, and 2–17 y, 2–5 y, 6–11 y, and 12–17 y, respectively, for polices3–6. In policies 2–6, children were vaccinated with LAIV. Policy 1 differed from policy 2only in the use of TIV instead of LAIV. Age groups were chosen to reflect the three stages inthe Thai education system (3–5 y, kindergarten; 6–11 y, elementary school; 12–17 y, secondaryschool). For the youngest age group we extended the age range to 2 y, the minimum age atwhich LAIV can be used. For comparison we also considered a policy of expanding annual coveragelevels with TIV to 66% in those aged at least 60 y (policy 7). In all other scenarios (includingpolicy 0), 10% of those aged 60 y and over were assumed to receive TIV annually. For agiven value of willingness to pay per disability-adjusted life year (DALY) averted (the cost-effectivenessthreshold), we consider the optimal policy to be the one with the highest expectedincremental net benefit (INB). The INB is the difference between the monetary value of healthgains (the product of the number of DALYs averted by the policy and the cost-effectivenessthreshold) and the costs of these health gains.We evaluated the sensitivity of our results to alternative assumptions about (i) mixing patternsbetween age groups, (ii) vaccine effectiveness, (iii) baseline immunity (prior to vaccination),(iv) vaccine coverage, (v) influenza transmissibility in Thailand, (vi) vaccine costs, and(vii) the probability that an influenza infection is symptomatic (Table 2).
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