After the team development, execution process should work on the planned timeline by team members in which each should perform the assigned tasks on the planned time. However, during any possible employee absence or vacation, the project manager should have a well-constructed leaving/vacation approval system is required to prevent the negative effects of time off. An employee absence would not only affect the original plan, but it could also negatively affect team members who are still working on the project. “According to a study by Kronos, 69% of employees surveyed say that unplanned absences add to their workload and 61% believe it increases stress. Being able to track absences and prepare for, or even prevent, unplanned days off can help eliminate changes in workload and the stress they cause.”
Thus, a backup plan is always required to avoid such circumstances, this can be included under the risk management criteria.

– Ref: blog.mavenlink