You can use MSXML XMLHTTP/ServerXMLHTTP to send dummy "HEAD" requests on a different thread to the server in order to keep the connection alive.
Example VBScript code:
Option Explicit
Dim objXMLHTTP
Set objXMLHTTP = CreateObject("MSXML2.XMLHTTP.4.0")
objXMLHTTP.open "HEAD", "http://www.yourserver.com/pageurl", False
objXMLHTTP.send
'wscript.echo objXMLHTTP.getAllResponseHeaders
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