Can My Kid Get a Flu Shot While Sick?

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My child finally had his appointment for a flu shot this morning (after rescheduling five times over the past two months due to various sicknesses). At the appointment, my husband called me saying my son had coughed (he had RSV two weeks ago) and we needed to reschedule yet again. My question is, what are the risk tradeoffs between vaccinating a child who might still be recovering from a previous illness (can it actually make their recovery worse?) versus just going through with it to help protect them from a possibly worse future illness? As we’ve gotten into “sick season,” it feels like we can’t seem to find a day when my kid isn’t sick to get him vaccinated, and I’m starting to worry that waiting is not the right call.

—Wanting to Get Vaxxed

There is a widespread belief among parents that kids shouldn’t get vaccines while they are sick. As you note, this can be extremely constraining. If we count “my child coughed” as being sick, most 2-year-olds are sick something like 85% of the time. Finding a vaccine appointment on the three days of the fall between illnesses feels like a fool’s errand.

A toddler gets a shot from a doctor — Getty

This widespread belief, though, is not based on science. Vaccines work by stimulating the immune system to develop antibodies. The immune system can do this even if it is also dealing with other threats. Even if a child is on antibiotics for something, vaccines will still work similarly — antibiotics kill bacteria, but should not impact the response to vaccination. The one exception to this is if a child is on an antiviral — say, if they are taking Tamiflu — it may make sense to wait. This guidance, by the way, comes from the logic of how vaccines work but also from the CDC. Even if your child has a fever, if the illness is mild, that is not a reason to delay vaccination.

What is true is that vaccines will often prompt an immune response that makes kids a little tired and cranky. So getting them vaccinated when they are sick might add to this, or maybe once they are sick, it’s all the same, so perhaps it’s a good idea to do it all at the same time!

To conclude, don’t wait. Get your kid vaccinated for the flu, even if they are a little sick at the time. The same goes for other vaccines — measles, etc. Your child can get them even if they are a little under the weather.