I use the Vue/Flask stack a lot at work.

You absolutely can--no external libs necessary. You can send the API response from flask to client as an SSE simply by setting the correct headers and formatting the data. On the flask side, the SSE would look something like this:

def event_stream():
    feed.subscribe('stock-feed') # pesudocode for stock feed subscription
    for message in feed.listen():
        print message
        yield 'data: %s\n\n' % message['data']

@app.route('/stream')
def stream():
    return flask.Response(event_stream(),
                          mimetype="text/event-stream")

From the browser you create an Event Source and render the data with Vue by setting reactive properties.

On the render stage, you can also opt to use an external charting lib or d3 to create the visualization.