Impact assessment of self-medication on COVID-19 prevalence in Gauteng, South Africa, using an age-structured disease transmission modelling framework

Introduction: Self-medication, as a global phenomenon, remains a pressing issue that requires attention worldwide, in particular, the Global South. It has been a hindrance to infectious disease control as it, in most cases dampens interventions put forth by health authorities. It is imperative, therefore, that disease dynamics relating to self-medication are incorporated into mathematical models used to inform infectious disease-related public health interventions and policy. COVID-19-associated self-medication is well documented, and its implications for disease prevention and control are alarming. We investigated the impact of self-medication across different age groups on the transmission dynamics of the disease; the interplay of vaccination and self-medication on the spread of the disease; and the age group with the most tendency for self-medication. We used Gauteng Province, South Africa, as a case study. Methods: : We employed ordinary differential equations (ODEs), formulated within an age-structured compartmental disease modelling framework. Model parameters were estimated using a Markov Chain Monte Carlo (MCMC) estimation scheme. Uncertainty and sensitivity analysis were carried out on model parameters. Results: : The model implied estimates indicates that self-medication is predominant among Age group 15-64 (83.13%), followed by Age group 65+ (44.17%). Age group 0-14 records 33.82%. The mean value of the basic reproduction number, first epidemic peak, and first epidemic peak time are 3.19838, 821536, and 214.988, respectively. Conclusion: Self-medicationplays a crucial role in combating COVID-19, and that regardless of the levelof effectiveness of instituted vaccination programs, it must be put in check. Appropriate campaign against COVID-19 related self-medication is justified. It is also worth noting that campaigns should target the active population (ages 14-64)