Before revision:  While mathematical models which capture the novel observations have been developed and analysed, they have many parameters and it is unclear whether the contributions of each immune component to cross-protection can be recovered from the data .
After revision:  While mathematical models which capture the novel observations have been developed and analysed, they have many parameters and it is unclear whether the contributions of each immune component to cross-protection , but also to gain insight into the immune response during a single infection .