As the COVID-19 continues to mutate, the number of infected people is
increasing dramatically, and the vaccine is not enough to fight the
mutated strain. In this paper, a SEIR-type fractional model with
reinfection and vaccine inefficacy is proposed, which can successfully
capture the mutated COVID-19 pandemic. The existence, uniqueness,
boundedness and nonnegativeness of the fractional model are derived.
Based on the basic reproduction number R 0 , locally stability and
globally stability are analyzed. The sensitivity analysis evaluate the
influence of each parameter on the R 0 and rank key epidemiological
parameters. Finally, the necessary conditions for implementing
fractional optimal control are obtained by Pontryagin's Maximum
Principle, and the corresponding optimal solutions are derived for
mitigation COVID-19 transmission. The numerical results show that humans
will coexist with COVID-19 for a long time under the current control
strategy. Furthermore, it is particularly important to develop new
vaccines with higher protection rates.