Six month old baby’s toddler sibling has a cold. Baby now starting to get sniffly. 6 month vaccines are booked for tomorrow. Should they be rescheduled?

What the evidence says

A runny nose from a mild cold is usually not a reason to put off vaccines. Canada's immunization guide is clear that mild illnesses, like an upper respiratory infection with a runny nose, sniffles, or even a low fever, do not raise the risk of vaccine side effects and do not stop the vaccine from working properly.

This matches advice from health authorities in other countries too. Doctors group illnesses into mild versus moderate or severe. Mild illness, even with some fever, is fine for vaccination. It's only moderate or severe illness, such as a baby who is very unwell, working hard to breathe, or not feeding, where doctors usually wait until the child recovers before vaccinating.

There is a practical reason for this rule too. Waiting does not give any health benefit, and delaying leaves your baby unprotected for longer against diseases like whooping cough and measles, which can be far more serious than a common cold.

That said, guidelines always leave room for judgment. If your baby's sniffles come with a high fever, unusual sleepiness, poor feeding, fast or laboured breathing, or you're just unsure, it's reasonable to call the clinic before the appointment. They can decide over the phone or examine your baby quickly at check-in.

So in most cases with just a bit of sniffling from catching a sibling's cold, you can go ahead with tomorrow's appointment as planned. Mention the sniffles to the nurse or doctor when you arrive so they can do a quick check before vaccinating.