MVC route option is persisting on reload (F5) of page - asp.net-mvc

Question

I have the following server side code in place in my MVC controller, it's a basic post, get, redirect pattern using model binding.
The problem is that after I submit the page it does the RedirectToAction sending the route option bool parameter correctly. But when I then reload the page (F5) it's still sending the route option parameter (bool) as the previous value (true), when I would expect it to send null. It seems as if the value is being persisted somehow.
Any Ideas on how to resolve this issue? Much appreciated.
Controller code:
[HttpGet]
public ActionResult DischargeHuman(bool? HumanDischarged = null)
{
DischargeHumanViewModel dischargeHumanVM = new DischargeHumanViewModel();
dischargeHumanVM.HumanDischarged = HumanDischarged;
return View(dischargeHumanVM);
}
[HttpPost]
public ActionResult DischargeHuman(DischargeHumanViewModel dischargeHumanVM)
{
string username = HttpContext.User.Identity.Name.Substring(HttpContext.User.Identity.Name.LastIndexOf(#"\")).Trim('\\');
dischargeHumanVM.UserName = username;
if (ModelState.IsValid)
{
dischargeHumanVM.HumanDischarged = _adminTaskLogic.DischargeHuman(dischargeHumanVM.ClientID.Value, dischargeHumanVM.HumanID, dischargeHumanVM.UserName, dischargeHumanVM.DateOfDischarge.Value);
}
if (dischargeHumanVM.HumanDischarged.Value)
{
return RedirectToAction("DischargeHuman", new { dischargeHumanVM.HumanDischarged });
}
else
{
return View(dischargeHumanVM);
}
}
.cshtml code:
#using (Html.BeginForm())
{
#Html.ValidationSummary();
if (Model.HumanDischarged.HasValue)
{
if (Model.HumanDischarged.Value)
{
<span style="color:blue" id="msgSpan">Human successfully discharged.</span>
}
else
{
<span style="color:red" id="msgSpan">An error occurred.</span>
}
Model.PatientDischarged = null;
}
...
view model:
public class DischargePatientViewModel
{
public string UserName { get; set; }
[Required]
[Display(Name = "Client: ")]
public int? ClientID { get; set; }
[Required]
[Display(Name = "Patient ID: ")]
public string PatientID { get; set; }
[Required]
[Display(Name = "Date Of Discharge: ")]
public DateTime? DateOfDischarge { get; set; }
public bool? PatientDischarged { get; set; }
public IEnumerable<SelectListItem> SelectClientList
{
get { return new SelectList(new ClientLogic().GetClients(null, false, true), "ClientID", "ClientDisplayText"); }
}
}