Intradermal pre-exposure rabies vaccination in a Canadian travel clinic: 6-year retrospective observational study.

Abstract

The intradermal route of vaccine administration for pre-exposure rabies prophylaxis, endorsed by the Canadian National Advisory Committee on Immunization, was implemented at a large travel clinic in Montréal in 2008. We evaluated the effect of intradermal vaccination availability on uptake of pre-exposure rabies prophylaxis and rates of seroconversion with intradermal vaccination. We conducted a retrospective cross-sectional study using data from December 2008 to December 2014. The number of travellers who received pre-exposure rabies prophylaxis before and after the introduction of intradermal vaccination was compared. Postvaccination antibody titres were measured in intradermal vaccination recipients. We compared demographic and travel characteristics between vaccinated and unvaccinated travellers and between travellers in the intradermal and intramuscular groups using univariate and multivariate analyses. The proportion of travellers who received pre-exposure prophylaxis increased after the introduction of intradermal vaccination (annual average of 300 travellers from December 2009 to December 2014 v. 183 travellers from December 2006 to December 2007). Seroconversion occurred in 99.9% of those in the intradermal group. Travellers who received pre-exposure prophylaxis were older (mean age 35.8 yr v. 32.1 yr) and had longer travel duration than those who did not receive pre-exposure prophylaxis. Travellers to Asia were more likely to receive pre-exposure prophylaxis, and travellers visiting friends and relatives were less likely to receive it. Travellers in the intradermal group were younger than those in the intramuscular group and were more likely to be travelling for tourism. The introduction of intradermal vaccination for pre-exposure rabies prophylaxis was associated with an increase in vaccination uptake. Reduced cost may be responsible for the increased coverage among younger travellers and those travelling for tourism. The high seroconversion rate after intradermal vaccination supports the effectiveness of this route of administration for pre-exposure rabies prophylaxis in immunocompetent people.