Vaccination is generally required when the baby is healthy, as most vaccines are antigens introduced into the human body to elicit an antibody response from the immune system. If a baby has a cold, it indicates a weaker immune resistance and possible bacterial or viral infection. Vaccinating in such a condition could potentially worsen the cold due to the already compromised immune system and may lead to other side effects such as high fever, rashes, or even other infections. Therefore, it is not recommended to vaccinate while the baby has a cold. It is better to wait a few days until the cold symptoms have completely subsided before vaccinating. Generally, delaying vaccination will not affect the baby and will be rescheduled according to the plan. Thus, it is best not to vaccinate when the baby has a cold.