Vaccinating for Marek's

So this is our first time raising chicks from day olds and hatching our own. We bought a few from a breeder which were vaccinated. A couple weeks later we bought a few more from the feed store which were not (and these are in a different brooder so there has been no cross contamination. We even wash before handling in a different brooder). Now we have our eggs hatching here soon and we have ordered the Marek's vaccine to get everyone caught up. Now when we do vaccinate if somehow we accidentally vaccinated a chick who had already been vaccinated by the breeder (I know they told me they weren't but just in case scenario here) would that hurt them???