In BC, can an employer require an employee to take their vacation leave in a non-unionized environment?

In BC, can an employer require an employee to take their vacation leave in a non-unionized environment? Scenario is such that the employer provides only 5 days of sick leave and is telling employees that they will be required to take there vacation leave now as there is a shortage of work. Employees wish to retain their vacation leave in case they fall ill in the next few months as they have no short term illness coverage.