There is a difference between worming and medicated starter feed for chicks.  Medicated starter typically is not medicated with a wormer, but rather a coccidistat.  Coccidistats are antiprotozoal agents to inhibit (but not totally prevent) the growth of cocci in the chicks GI tract.  What this does is prevent an overabundance of coccidia growth which can kill the chick, giving the chicks own immune system time to kick in and develop an immunity. 
As for using an actual wormer in chicks, IMO it is not a good idea.  Chickens, like most other animals, can handle a small wormload just fine.  Unless exposed to unusually filthy conditions, chicks haven't been alive long enough to develop a heavy wormload. 
There are three main camps on worming chickens.  One camp doesn't worm, at all.  The next worms, but using only natural products (which, again IMO, aren't proven to effectively eradicate worms.  Inhibit maybe, but not wipe out a full blown infestation.).  The third camp believes in regular worming as part of regular maintenance.  I fall into the third camp.  I start worming around 9 months old in my chickens and once a year thereafter.  I don't mess around with wazine, which only kills roundworms.  I start with a broad spectrum wormer and that's what I use each year.