I've read news reports that the predominant flu strain right now is esp. bad and the vaccine is only marginally effective. should i be concerned?

No big worries: The current vaccine indeed is only partly effective in preventing influenza. However, the influenza itself isn't much more severe than average. Use common sense to avoid exposure (fist or elbow bump instead of shaking hands), avoid obviously ill people, frequent hand washing or alcohol gel, and prompt Rx if you get flu symptoms (fever, cough, headache, muscles aching). Otherwise live normally.