Well we rarely lose one in the following 20 days after calving.  Usually see purple gut hit in the 30-60 day range and only at the end of the season which is now when it is getting warm and wet.  So those late calves might get a C&D shot at birth but other than that nothing does.  Cow is vaccinated before calving and calves are vaccinated at branding which is usually in the 30-60 day old window.  Death loss from calving varies on too many things, we had under 1% last year, actually lost more cows than calves, but also youngest cows were 4, big difference from calving a bunch of heifers.  This year is looking to be a hair over 1% youngest cows now 5.  If we are calving heifers and have some bad storms normal will be in the 3% range.  Didn't lose any from calving to just before precon last two years.

All that said vaccinating has nothing to do with our calving death loss.  Has everything to do with post calving scours and purple gut though.  Second highest death loss is usually right before preconditioning either from lightning, or that is about the age a calf with some kind of genetic issue finally dies from it.  I've never seen pneumonia in little calves, get one or two in July each year but that is about it until weaning.

And yes we try to keep in groups of 20 days or so, usually just do it by the hundred head which will come out to about every 20 days.  Good group on age and not too many you can't really look them all over when feeding.