Send follow-up campaign e-mail to those who haven't viewed original?

Is it possible to send a follow-up e-mail for the e-mail campaign for those who haven’t yet viewed the e-mail? Or would I have to setup a duplicate campaign and remove the non-applicable people from the target list?

Also, should I have confidence with the trackers accuracy, meaning if it doesn’t show, I should assume they definitely haven’t read the e-mail?

Thanks!