Tropis needle-free injector for fractional-dose IPV administration: A pilot study for integration into routine...

Fractional-dose inactivated poliovirus vaccine (fIPV), 1/5th of a standard IPV dose, is used in Cuba's routine immunization (RI) schedule. Tropis, a needle-free jet injector, simplifies intradermal fIPV administration and was piloted in Camagüey, Cuba, from 2019 to 2020. This study assessed Tropis' acceptability, safety, and immunogenicity compared to traditional needle and syringe (N/S) administration. Surveys were administered to parents/guardians (n = 5260) and nurses (n = 66) to evaluate satisfaction. Blood samples from vaccinated children were analyzed for neutralizing poliovirus antibody levels (n = 231 in Camagüey piloting Tropis; 138 in Ciego de Ávila using N/S). Results indicate 98 % of parents and 98.5 % of nurses preferred Tropis over N/S. Adverse events were fewer with Tropis than N/S (6 % [14/238] vs. 13 % [20/157], p = 0.028). After two doses at 4 and 8 months, there was no significant difference between Tropis and N/S administration in seroprevalence levels for all three serotypes (type 1, 76.2 % vs. 79 %, p = 0.53; type 2, 80.5 % vs. 84.1 %, p = 0.39; type 3, 51.6 % vs. 64.5 %, p = 0.08). Although Tropis acceptability seemingly supersedes standard N/S administration (in both parents and nurses) and the achieved seroprevalence did not differ significantly, the government of Cuba did not implement Tropis into its RI program due to increased costs associated primarily with the syringe.