1. World Health Organization. Immunization in practice: module 6 holding an immunization session. Immunization in Practice: A practical resource guide for health workers–2004 update. 2004:1-29. 2. Crawford CL, Johnson JA. To aspirate or not: an integrative review of the evidence. Nursing2020 Critical Care. 2012 Sep 1;7(5):9-15. 3. Sepah Y, Samad L, Altaf A, Halim MS, Rajagopalan N, Khan AJ. Aspiration in injections: should we continue or abandon the practice?. F1000Research. 2014;3. 4. Herraiz-Adillo Á, Martínez-Vizcaíno V, PozueloCarrascosa DP. Aspirar antes de la inyección de vacunas intramusculares, ¿debería el debate continuar? Enferm Clín. 2022;32:65–66. 5. Girish G.N., Ravi M.D. Vaccination related pain: comparison of two injection techniques. Indian J Pediatr. 2014;81:1327–1331. doi: 10.1007/s12098-014-1347-1.