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

Long-term serological response and boostability of intradermal rabies immunization: A retrospective chart review

OBJECTIVES

Rabies vaccines in Canada are currently labeled for intramuscular use only; however, intradermal vaccine administration may be equally effective. This study aims to assess the immediate and long-term (≥ 2 years) serological response and boostability of intradermal administration of rabies vaccine for pre-exposure prophylaxis.

METHODS

This retrospective cohort study was conducted using data from electronic medical records at the Winnipeg Regional Health Authority Travel Health & Tropical Medicine Services Clinic. Individuals ≥ 18 years of age at time of vaccination who received at least 3 × 0.1 mL doses of intradermal rabies vaccine were included. All charts were reviewed to extract post-primary immunization and post-booster serology results, and t-tests were conducted to evaluate seroprotection (defined as serology ≥ 0.5 IU/mL).

RESULTS

A total of 324 individuals received an intradermal rabies primary pre-exposure vaccination series with follow-up serology within 90 days. Seroprotection was observed in 96% (GMT = 3.36 IU/mL, 95% CI 3.07-3.68). Of these, 68 had serology results 1.8-2.5 years later, with seroprotection declining to 44% (GMT = 0.52 IU/mL, 95% CI 0.41-0.65). However, 100% seroprotection was observed in those who received an intradermal booster dose at ≥ 2 years with follow-up serology (n = 20, GMT = 4.7 IU/mL, 95% CI 3.7-6.2).

CONCLUSION

Intradermal administration of a primary pre-exposure rabies vaccine series demonstrates a strong serological response. While titers decline over time, the robust serological response demonstrated after a single intradermal booster vaccine dose suggests that a strong anamnestic immune response was maintained. This finding supports existing evidence that intradermal administration of rabies vaccines can be used effectively for rabies pre-exposure and post-exposure prophylaxis.

Rabies vaccination strategies in the Netherlands in 2018: a cost evaluation

BackgroundThe risk of contracting rabies is low for travellers. However, the number of Dutch travellers potentially exposed abroad following an animal-associated injury and needing post-exposure prophylaxis (PEP) has increased, resulting in increased costs.AimHere, we evaluated the costs and the cost-effectiveness of different pre- and post-exposure interventions in the Netherlands, taking into account the 2018 World Health Organization (WHO) recommendations for the prevention of rabies.MethodsA decision tree-based economic model was constructed. We calculated and compared the cost of different WHO pre-exposure prophylaxis (PrEP) recommendations, intramuscular vs intradermal vaccination and PEP subsequent to increased vaccination coverage in risk groups. We estimated cost-effectiveness, expressed as incremental costs per rabies immunoglobulin (RIG) administration averted, using a societal perspective. Statistical uncertainty regarding number of travellers and vaccination coverage was assessed.ResultsTotal costs at the national level were highest using previous WHO recommendations from 2012, estimated at EUR 15.4 million annually. Intradermal vaccinations in combination with the current recommendations led to the lowest costs, estimated at EUR 10.3 million. Higher vaccination uptake resulted in higher overall costs. The incremental costs per RIG administration averted varied from EUR 21,300-46,800.ConclusionsThe change in rabies PrEP and PEP recommendations in 2018 reduced total costs. Strategies with increased pre-travel vaccination uptake led to fewer RIG administrations and fewer vaccinations after exposure but also to higher total costs. Although larger scale intradermal administration of rabies vaccine can reduce total costs of PrEP and can positively influence vaccination uptake, it remains a costly intervention.