Histopathology scores in mice.

aCellular infiltrate (0–6): 0, none; 1 mild, multifocal; 2 mild, widespread or moderate multifocal; 3, mild widespread and moderate multifocal or severe multifocal; 4, moderate widespread; 5, moderate widespread and severe multifocal; and 6, severe widespread. Mucus metaplasia and functional atrophy (0–3): 0, absent; 1 mild; 2 moderate; and 3 severe. *p<0.05, **p<0.01, c.f. unvaccinated/challenged group; One-way ANOVA with Dunnett’s Multiple Comparison Test