Use of booster inoculations to sustain the clinical effect of an adjuvant breast cancer vaccine: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

Cancer. 2011 Feb 1;117(3):463-71. doi: 10.1002/cncr.25586. Epub 2010 Sep 15.


Background: The authors are conducting clinical trials of the HER-2/neu E75-peptide vaccine in clinically disease-free breast cancer (BC) patients. Their phase 1-2 trials revealed that the E75 + granulocyte-macrophage colony-stimulating factor (GM-CSF) vaccine is safe and effective in stimulating clonal expansion of E75-specific CD8(+) T cells. They assessed the need for and response to a booster after completion of primary vaccination series.

Methods: BC patients enrolled in the E75 vaccine trials who were ≥6 months from completion of their primary vaccination series were offered boosters with E75 + GM-CSF. Patients were monitored for toxicity. E75-specific CD8(+) T cells were quantified using the human leukocyte antigen-A2:immunoglobulin G dimer before and after boosting.

Results: Fifty-three patients received the vaccine booster. Median time from primary vaccination series was 9 months (range, 6-35 months), and median residual E75-specific immunity was 0.70% (range, 0-3.49%) CD8(+) lymphocytes. Elevated residual immunity (ERI) (CD8(+) E75-specific T cells >0.5%) was seen in 94.4% of patients at 6 months from primary vaccination series versus 48% of patients at >6 months (P = .002). The booster was well tolerated, with only grade 1 and 2 toxicity observed. Local reactions were more robust in patients receiving the booster at 6 months from primary vaccination series compared with those at >6 months (99.4 ± 6.1 mm vs 81.8 ± 4.1 mm, P = .01). In patients lacking ERI, 85% had increased ERI after vaccination (P = .0014).

Conclusions: The HER-2/neu E75 peptide vaccine E75 stimulates specific immunity in disease-free BC patients. However, immunity wanes with time. A vaccine booster is safe and effective in stimulating E75-specific immunity in those patients without ERI. These results suggest that the booster may be most effective at 6 months after completion of the primary vaccination series.

Publication types

  • Clinical Trial, Phase I
  • Clinical Trial, Phase II
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Breast Neoplasms / immunology
  • Breast Neoplasms / therapy*
  • CD8-Positive T-Lymphocytes / immunology
  • Cancer Vaccines / therapeutic use*
  • Female
  • Humans
  • Immunization, Secondary* / adverse effects
  • Interferons / analysis
  • Middle Aged
  • Receptor, ErbB-2 / immunology
  • Time Factors
  • Vaccines, Subunit / therapeutic use*


  • Cancer Vaccines
  • Vaccines, Subunit
  • Interferons
  • Receptor, ErbB-2