A Randomised, Double-Blind Pilot Study of Enzyme-Potentiated Desensitisation for Prophylaxis of Large Local Reactions to Mosquito Bites

Abstract EN

Primary Objective.

To test the hypothesis that two injections of enzyme-potentiated mosquito antigen significantly reduce the size of experimental mosquito bites in participants with LLR-MB.

Design.

Randomised, double-blind, placebo-controlled, parallel group comparison over 3 months.

Setting.

Hospital outpatient clinic.

Participants.

Fifty adult participants of both sexes.

Interventions.

Two injections of mosquito antigen or matching placebo, 6 weeks apart.

Main Outcome Measures.

Early (1 hour) and late (24 hours) mean square root of erythema area (SREA) following controlled mosquito bite with the second bite given at least 6 weeks following the final injection.

Results.

At 1 hour, mean SREA was slightly higher in the EPD group compared to placebo after adjusting for baseline values (0.46, 95% CI −6.11 to 7.03), but this was not statistically significant (P=0.89, ANCOVA analysis); neither were the results at 24 hours (−2.58, 95% CI −11.73 to 6.57) (P=0.57).

The proportion of participants experiencing a decrease in wheal size at 1 or 24 hours was similar between groups.

Conclusions.

EPD was not demonstrated to be effective for immediate or delayed LLR-MB.

Methodological problems included a high variability in LLR-MB between subjects, suggesting that a crossover design should be used in future.