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Table 1 Considerations of different field trial design options for second-generation malaria vaccines

From: MALVAC 2012 scientific forum: accelerating development of second-generation malaria vaccines

Field efficacy trial options 2nd generation vs placebo 2nd generation vs 1st generation 1st/2nd generation vs 1st generation 1st/2nd generation vs 1st generation vs placebo
Estimate of efficacy Absolute efficacy estimated. Relative efficacy estimated. Relative efficacy estimated. Absolute and relative efficacy estimated.
Type of assessment Superiority to no treatment. Non-inferiority to 1st generation or superiority to 1st generation. Superiority to 1st generation. Superiority to 1st generation and to no treatment.
Limitations and Considerations May be considered unethical to randomize to placebo, if 1st generation vaccine is available and recommended. Large sample sizes may be needed. Non-inferiority design would not show progress towards the 80% effective goal in the label, but could make alternative vaccines available. Large sample sizes may be needed. 1st and 2nd generation vaccines could be given together or as prime-boost strategy. Very large sample sizes may be needed (may not be feasible). May be considered unethical to randomize to placebo, if 1st generation vaccine is available and recommended. This design would not demonstrate efficacy of the 2nd generation vaccine independent of the 1st generation vaccine.
  Efficacy relative to 1st generation vaccine would not be known Efficacy relative to no treatment would not be known. Efficacy relative to no treatment would not be known.