To date, there has been no evidence-based guidance regarding the rate at which vaccines should be injected to minimize pain. This has led to a disparity in practice. Some vaccinators favour a slow rate of injection (around 8-10 sec/mL) while others prefer a more rapid rate of injection (around 2-4 sec/mL).The slow injection method leads to a longer needle dwelling time with the increased possibility of the needle moving around and causing pain by damaging muscle tissue. Rapid injection, on the other hand, may lead to a sudden distension of muscle tissue, which itself could be painful. Allowing the muscle sufficient time to distend in order to accommodate the vaccine might minimize pain. This study will address the identified knowledge gap by comparing pain in infants undergoing routine vaccinations with a fast vs. slow injection speed.