Safety of purified Vero cell rabies vaccine manufactured in Pakistan: A comparative analysis of intradermal and intramuscular routes.

BACKGROUND: Rabies vaccines are conventionally given via the intramuscular (IM) route; however, switching the route of administration from IM to intradermal (ID) without affecting efficacy can be advantageous in terms of cost, dosing, and time. Hence, it is indispensable to evaluate its safety along different routes. This study was carried out to ascertain the frequency of adverse drug events (ADEs) and associated factors, as well as to compare safety based on the IM and ID routes.

METHODS: A prospective observational study was carried out on 184 individuals with rabies exposure. The vaccination schedules for post-exposure prophylaxis (PEP) included 0.2 milliliter (ml) of purified Vero cell rabies vaccine (PVRV) administered ID at two different sites with 0.1ml each on days 0, 3, and 7 in first group (3-dose regimen ID) and 0.5 ml administered IM on days 0, 3, 7, 14, and 28 in the second group (5-dose regimen IM). The safety of the vaccines was determined by reviewing ADEs during physical examinations and follow-up. ADEs were characterized by local and systemic effects.

RESULTS: Of the total, 99 (53.80%) patients reported ADEs. Those who reported local and systemic ADEs were 80 (43.48%) and 59 (32.06%), respectively, while simultaneous occurrence was reported in 40 (40.40%) patients. The most frequent local ADE 76 (41.30%) reported was pain followed by erythema 18 (9.78%). Additionally, fever was in highest proportion 25 (13.59%) for systemic effects, followed by headache 15 (8.15%). The patients reported with ADEs by the IM and ID routes was comparable (p > 0.05). Similarly, both local and systemic effects were also comparable (p > 0.05).

CONCLUSION: Half of the study participants reported ADEs. Almost similar proportions of local and systemic effects were observed. Likewise, the ADEs recorded were comparable for both routes. PVRV carries very low safety concerns with either route for administration.