Figure 1.

Dose-optimization and efficacy studies using the 2012–2013 influenza vaccine formulations in cotton rats. (a,b) Dose–range study of immunogenicity of FluLaval 2012–2013 during the corresponding vaccine season (VSeason: 2012–2013). Young animals were immunized intramuscularly (i.m.) twice (with 3 weeks in between) with the indicated doses of FluLaval or infected intranasally (i.n.) once with influenza A/Victoria (H3N2) (Vict) and blood was collected for analysis of serum HAI titers (a) or binding IgG (b) against FluLaval 2012–2013 three weeks after the last immunization or 6 weeks after A/Victoria infection. Results represent GMT±SE for 8–10 animals per group. Negative control animals (Ctr) were unimmunized and uninfected. (c) Efficacy of FluLaval 2012–2013 and FluMist 2012–2013 in the young and aged cotton rats. Animals immunized once with FluLaval or FluMist were infected i.n. with A/California (A/Cal) three weeks later and sacrificed 1 day later for analysis of influenza load in the lung by qPCR. Control animals were infected with A/Cal and re-infected 3 weeks later (secondary infection, °2) or mock immunized and infected with A/Cal (primary infection, °1). Results represent GMT±SE for 5 animals per group. *p< .05 when compared to influenza M mRNA level in the same age animals with primary infection. No significant differences were found between influenza M mRNA levels in animals of different ages treated the same way