Cavalry 9 & Covexin 8 are to polyvalent Clostridial bacterin/toxoids that contain tetanus toxoid.
I generally use Cavalry 9; 2ml dosage - and I don't get nearly as big a 'knot' at injection sites as I've typically gotten with the 5ml dose for other Clostridium bacterin/toxoids.
I'm sure there have been millions of baby calves banded with the green cheerio with no issues, but I see full-blown cases of tetanus in them from time to time; is it just 'good luck' that they didn't come down with it, or did they get maternal protection? I don't know - but I'd hazard a guess that most cows in the USA are not vaccinated against tetanus, so the maternal antibody deal is unlikely, in my estimation.
First case of tetanus I ever saw was in one of my own bulls, knife-castrated at about 400 lbs - found him sawhorsed in the pasture about two weeks later. I've castrated every other bull on the place since then with the Burdizzo emasculatomes; only thing I use the green cheerio for is removing the occasional horn that shows up here.
Lost a nice 4 mo. old heifer to tetanus about 4 years ago; since then, we've switched to using Cavalry 9, to get tetanus protection, rather than the old 5-way Clostridial bacterin/toxoids.
We usually try to get first dose in them around 10 days of age, then booster 3-6 weeks later. Worked the spring calves yesterday... most were about 4-6 weeks old... we just didn't get it done earlier. With bottle babies you should have no issue getting 'em done. Ideally, you'd want to vaccinate at least 2 weeks prior to band application, and booster at the time you put the band on - or, give a dose of tetanus antitoxin AND a dose of bacterin containing tetanus toxoid (not both in the same injection site) at the time of band application, then booster the bacterin/toxoid as indicated on the product label.
The Clostridial bacterin/toxoids do require refrigeration. You can 're-use' unused portions for up to 4 months after intial 'entry' - provided you keep it refrigerated - and didn't contaminate the product. That means... insert a new sterile needle in the stopper, draw out doses as needed, removing syringe from needle and attaching a different needle for injections - no 'in and out' of the vaccine bottle with needles that have been used for injections.