27/08/2026
Medical experts recommend delaying vaccines during a moderate or severe illness primarily for safety monitoring and comfort, not because the vaccine will fail.
According to guidelines from the [Centers for Disease Control and Prevention](https://www.cdc.gov/vaccines/hcp/imz-best-practices/contraindications-precautions.html) (CDC), the three main reasons to postpone are: [1]
# # 1. Avoiding "Diagnostic Confusion"
Vaccines can sometimes cause mild, temporary side effects like a low-grade fever, fussiness, or light stomach upset. If a baby is already moderately or severely sick with diarrhea, adding vaccine side effects makes it very difficult for you and your doctor to figure out what is happening. [1, 2, 3]
* Example: If a fever spikes, is it a normal reaction to the vaccine, or is the underlying stomach illness getting dangerously worse?
# # 2. Not Overloading a Distressed Body
While a baby’s immune system is incredibly strong and can easily handle vaccines during a mild cold, a moderate-to-severe illness causes real physical stress. Severe diarrhea puts an infant at high risk for dehydration. Doctors prefer not to layer potential vaccine side effects (like vomiting or additional fussiness) on top of a child who is already struggling to stay hydrated and comfortable. [1, 4]
# # 3. Specific Complications with Oral Vaccines
If your 7-month-old is scheduled for the oral rotavirus vaccine (which is swallowed as drops), having active, severe diarrhea or vomiting means the body may pass the liquid too quickly for it to be fully effective. Furthermore, because mild diarrhea is a known, temporary side effect of the rotavirus vaccine itself, giving it during a severe bout of stomach flu will only worsen the intestinal distress. [2, 5, 6, 7]
# # How to Tell the Difference
* Green Light (Vaccinate): The baby has a loose stool or two, but is smiling, playing, eating normally, and staying hydrated.
* Yellow Light (Postpone): The baby has frequent, watery stools, is refusing fluids, has a high fever, or seems unusually weak and lethargic. [4, 8]
To help narrow down the next steps, feel free to share:
* Are there any other symptoms present, such as a fever or vomiting?
* Is your baby able to keep fluids down and producing normal wet diapers?
If you have a discharge summary or a health notice from a recent clinic visit, you can also share a photo of it so I can look for specific provider notes.
[1] [https://www.cdc.gov](https://www.cdc.gov/vaccines/hcp/imz-best-practices/contraindications-precautions.html)
[2] [https://www.cdc.gov](https://www.cdc.gov/vaccine-safety/vaccines/rotavirus.html)
[3] [https://www.cdc.gov](https://www.cdc.gov/vaccines-children/about/index.html)
[4] [https://kidshealth.org](https://kidshealth.org/en/parents/rotavirus-vaccine.html)
[5] [https://www.cdc.gov](https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-19-rotavirus.html)
[6] [https://www.merckmanuals.com](https://www.merckmanuals.com/professional/infectious-diseases/immunization/rotavirus-vaccine)
[7] [https://nrpeds.com](https://nrpeds.com/getattachment/Education/Keeping-Your-Child-Healthy/Recommended-Well-Visit-and-Immunization-Schedule/Rotavirus-Vaccine.pdf.aspx?lang=en-US)
[8] [https://www.babycenter.com](https://www.babycenter.com/health/doctor-visits-and-vaccines/should-immunizations-be-postponed-if-my-child-is-sick_11212)
