asp button with single click and not multiple clicks

I have a "next" button which gray out after click next so the screen reader read "NEXT IS DISABLED". How can I disable "NEXT IS DISABLED" from screen reader? I tried aria-hidden=true or aria-disabled=true but it did not work. Please advise. Thanks.

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<asp:Label ID="lblNext" runat="server" Text="&nbsp;" Visible="False" />
                <GSI:GSIButton ClickOnce="true"  ID="btnNext" runat="server" aria-disabled="true" CssClass="formbutt" OnClick="GotoNextPage" Text="<%$ Resources: Resource, _Next %>" aria-label="<%$ Resources:Resource,lbtnNext %>" />
 
Protected Sub GotoNextPage(ByVal sender As Object, ByVal e As System.EventArgs)
        _GoNextEventHandler.Invoke(sender, e)
    End Sub
Public Property ClickOnce As Boolean
            Get
                Return _ClickOnce
            End Get
            Set(value As Boolean)
                _ClickOnce = value
            End Set
        End Property
Private Sub EmitClickOnceJS()
            If ClickOnce Then
                Dim js As New StringBuilder
 
                'function to disable button if it was then element which caused postback
                js.AppendLine("<script type='text/javascript'>")
                js.AppendFormat("function DisableButton_{0}()", Me.ClientID)
                js.AppendLine("{")
                js.AppendFormat(" if(document.activeElement.id=='{0}') document.getElementById('{0}').disabled=true;", Me.ClientID)
                js.AppendLine()
                js.AppendLine("}")
 
                'ensure this function is caused when posting back using before unload
                js.AppendFormat("$(window).on('beforeunload',DisableButton_{0})", Me.ClientID)
                js.AppendLine()
 
                'async begin request disable if this button was cause of postback
                js.AppendLine("var postbackElement;")
                js.AppendLine("$(document).ready(function(){")
                js.AppendLine(" try {")
                js.AppendLine("         Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(function(sender,args)")
                js.AppendLine("         {")
                js.AppendLine("          postbackElement = args.get_postBackElement();")
                js.AppendFormat("        if(postbackElement.id=='{0}') document.getElementById('{0}').disabled=true;", Me.ClientID)
                js.AppendLine("         });")
                js.AppendLine("     }catch(e){}")
                js.AppendLine("});")
 
                'async end request enable if this was the button which caused postback
                js.AppendLine("$(document).ready(function(){")
                js.AppendLine(" try {")
                js.AppendLine("         Sys.WebForms.PageRequestManager.getInstance().add_endRequest(function(sender,args)")
                js.AppendLine("         {")
                js.AppendFormat("           if(postbackElement.id=='{0}') document.getElementById('{0}').disabled=false;", Me.ClientID)
                js.AppendLine("         });")
                js.AppendLine("     }catch(e){}")
                js.AppendLine("});")
                js.AppendLine("</script>")
 
                'register the js
                If Not Page.ClientScript.IsClientScriptBlockRegistered(String.Format("disable{0}", Me.ClientID)) Then
                    Page.ClientScript.RegisterClientScriptBlock(Page.GetType, String.Format("disable{0}", Me.ClientID), js.ToString())
                End If
 
            End If
 
        End Sub