It is generally recommended to focus on a healthy and balanced diet to ensure that a child receives all the necessary nutrients for a strong immune system. In some cases, a supplement of vitamins may be considered, but it is advisable to consult a nutritionist for personalized advice. Probiotics have shown benefits in preventing intestinal disorders, but their effectiveness against viruses like the common cold is still being researched. Breastfeeding is the best way to provide essential nutrients and antibodies to a baby, offering passive immunity. If you have any further questions or concerns, it is always best to seek advice from a healthcare professional.