There is no way you can stop getting inflected from common cold additional measures such as improving your water intake having more of vitamin c in your diet improves immunity

Viruses tend to infect individuals not only children but even elders of any age these continuously keep changing depending upon the host environment and hence still the world is battling viruses. If your question is related to coronavirus please specify or if it is only related to normal cough and cold it is to build immunity children up to 5 years of age are in a process of building immunity naturally and via vaccinations