Fig. 5

a Model schematic, which includes susceptible (S), exposed (E), vaccinated against chickenpox (\(V_{VZ}\)), infected with chickenpox (\(I_{VZ}\)), vaccinated against shingles (\(V_{HZ}\)), recovered from chickenpox (\(L_1\)), infected with shingles (\(I_{HZ}\)), and recovered from shingles (\(L_2\)) classes. Births entered the model through either the S class or the vaccinated against chickenpox (\(V_{VZ}\)) class depending on chickenpox vaccination (i, ii). Natural death occurred in all classes and is indicated by an arrow leaving each class at the bottom. b Vaccination simulations varied by chickenpox vaccination roll-out (i), chickenpox vaccination uptake (ii), shingles coverage (iii), and length of shingles immunity (iv). A model without any vaccination was also simulated where all values \((i)-(iv)\) were set to 0