I need opinions. We have a 3.5 month old chihuahua yorkie mix. She got her third booster shot on Thursday and has vomit

She got her third booster shot on Thursday and has vomited once each night since then. However, she acts 100% normal before and after. The vomit looks like food that wasn't chewed well enough. The vomiting is happening awhile after she has eaten. Should we be concerned? The vet isn't open until Monday so we are trying to decided if we should call the on-call vet. Thanks!