Depletion of CD4 T cells during neoadjuvant vaccination significantly improves survival outcome after debulking surgery. All groups of AB1-HA bearing BALB/c mice (n = 10) received 75% debulking surgery on day 18 (dotted line). Vaccinated mice received rMVA-HA i.p. 7 days apart (P/B) and depleting antibodies (black arrows) were given every 3 days, starting 1 day prior to the first vaccination (q3dx4). Surviving mice were rechallenged on day 81 (black triangle). (A) Tumor growth and survival data showing delay in tumor growth after combined therapy compared to surgery only. Complete tumor regression was only observed when combined therapy was performed in the absence of CD4 T cells (open triangle). (B) Data from repeat experiments showing overall survival following surgery or vaccination as individual or combined therapies, with or without CD4 T cell depletion. Depletion of CD4 T cells significantly improved the survival outcome relative to non-depleted controls. All surviving mice resisted tumor rechallenge. **p < 0.01, ***p < 0.001. All significant Logrank comparison are to respective untreated controls.