Vitinho explained that jet injectors, like the Ped-O-Jet, used high pressure to pierce the skin, and did not just spray the liquid on it. According to him, the use was abandoned due to the risk of cross-contamination: the reusable nozzle could receive splashes of blood from a previously vaccinated person and transmit hepatitis B and C or HIV. Vitinho stated that there was an outbreak associated with the method, after which the WHO stopped recommending it, and that the United States Army banned its use in 1997. In Brazil, he said, the guns were used in mass vaccination campaigns in the 1970s, including the meningitis campaign in 1975, and were also abandoned due to the risk of contamination. He added that currently only models with disposable cartridges exist and that the change was not related to the pain caused by the injection. #saúde #vacinação #história (translated)