Ramadan, P. A., Araújo, F. B. de and Ferreira Junior, M. (2001) “A 12-month follow-up of an influenza vaccination campaign based on voluntary adherence: report on upper-respiratory symptoms among volunteers and non-volunteers”, São Paulo Medical Journal, 119(4), pp. 142–145. Available at: https://periodicosapm.emnuvens.com.br/spmj/article/view/2770 (Accessed: 16 October 2025).