Can children take vaccination pills instead of injections in their arms?

Digestion limits. Medication that is not altered by digestive juices in the stomach or intestines can be taken as a pill or liquid, be absorbed & work. If a medication/vaccine is altered by digestion or if the medication in needed quickly or at high levels a bypass method is needed. When appropriate, a patch can be used for some meds, but injection remains a dependable go to method .
Depends. Some medications can be taken orally or injected. In that case, so long as the child can swallow pills (or liquid forms) then it should be fine. However, some medications can only be injected and not taken orally as they are rendered inactive or simply not absorbed by the digestive system.