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Symptom guide · Pregnancy Smart

Fever after baby vaccines

Assigned clinical reviewerSharyn Harrison· CNM, NPDraft · pending clinical reviewUpdated

What does the evidence show for fever after baby vaccines?

  • Most fevers after childhood vaccination begin within the first day or two and are a normal, self-limited reaction rather than a sign that something is wrong. Comfort measures include a cool, damp cloth on the injection site, a lukewarm sponge bath, and extra fluids, since some babies eat less in the 24 hours after a shot. 1
  • Febrile seizures after vaccination are uncommon. When flu, pneumococcal, and DTaP vaccines are given together, studies found at most about 30 febrile seizures per 100,000 vaccinated children, with an elevated window in the 24 hours after the combined doses. These seizures do not cause lasting harm and most children recover within minutes. 2
  • A baby younger than 3 months old with any fever of 100.4°F (38°C) or higher, taken rectally, needs prompt contact with a medical provider. A temperature of 105°F (40.5°C) or higher at any age is an emergency unless it responds quickly to care, and a fever lasting more than 48 hours in a child under 2 also warrants a call. 3
  • Parents should contact their child's provider right away if a baby develops a high fever after vaccination, becomes inconsolable, or is noticeably less active than usual, rather than waiting to see if the symptoms pass on their own. 4

When to act on a fever after vaccination

SituationWhat to do
Fever starts within 1 to 2 days, baby is 3 months or older and mostly acting like themselvesComfort measures at home; call if it lasts more than 2 days
Any fever, 100.4°F (38°C) or higher rectally, in a baby younger than 3 monthsContact your pediatric provider the same day
Temperature of 105°F (40.5°C) or higher at any ageSeek prompt medical care unless it comes down quickly with care
Difficulty breathing, blue-tinged lips, a stiff neck, a seizure, or a baby who cannot be wokenCall 911 or go to an emergency department

When should I call my provider about fever after baby vaccines?

Any fever in a baby younger than 3 months, 100.4°F (38°C) or higher taken rectally, needs same-day medical contact even when a recent vaccine is the likely cause. A temperature of 105°F (40.5°C) or higher at any age, or a fever lasting more than 2 days in a child under 2, also needs medical evaluation rather than continued home care. Call 911 or go to an emergency department for difficulty breathing, blue-tinged lips or tongue, a stiff neck, a seizure, or a baby who cannot be woken or consoled. If you are ever unsure which side of the line you are on, make the call. Obstetric teams handle these check-ins as routine, not as overreacting.

Frequently asked questions

How soon after a shot does a fever usually start, and how long does it last?

Most vaccine-related fevers show up within the first day or two after the appointment and ease on their own within 1 to 2 days. A fever that starts well outside that window, or drags on past 2 days, is worth a call rather than more waiting.

What temperature actually counts as a fever I should act on?

A rectal temperature of 100.4°F (38°C) or higher counts as a fever in babies. For a baby younger than 3 months, that number alone is reason to call the provider the same day, regardless of how the baby otherwise seems.

My baby is younger than 3 months and has a fever after a shot. What should I do?

Call your pediatric provider right away rather than managing it at home first. Fever in this youngest age group is evaluated differently than in older babies, and a recent vaccine does not change that threshold.

Can a vaccine cause a febrile seizure?

It is uncommon. Combined flu, pneumococcal, and DTaP vaccination has been linked to at most roughly 30 febrile seizures per 100,000 children vaccinated, mostly within 24 hours of the visit. The seizures themselves are frightening to watch but do not cause lasting harm.

How can I make my baby more comfortable after shots?

A cool, damp cloth on the injection site can ease soreness and swelling, and a lukewarm sponge bath can help bring a fever down. Offer fluids often, since many babies eat a little less in the first day after vaccination, and ask your pediatrician about an appropriate fever reducer if needed.

Is it normal for my baby to be extra fussy or sleepy after vaccination?

Some fussiness, sleepiness, or a smaller appetite in the first day or two is common and expected. What is not expected is a baby who becomes inconsolable or is clearly less responsive than usual, which is a reason to call rather than just wait it out.

What symptoms after a shot mean I should call the doctor right away instead of just watching?

Call promptly for a high fever in a baby younger than 3 months, a temperature of 105°F (40.5°C) or higher at any age, a fever lasting more than 2 days, or a baby who seems inconsolable or much less active than usual. Go to an emergency department for breathing trouble, blue-tinged lips, a stiff neck, a seizure, or a baby who cannot be woken.

How is a fever right after a vaccine different from a fever caused by an illness?

A fever tied to a shot almost always starts within a day or two of the appointment and resolves within another day or two on its own. A new fever with no recent vaccine, or one that starts well after that window, is evaluated the same way any unexplained infant fever would be, using your baby's age and how they are acting rather than assuming it will pass.

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References

  1. Before, During, and After Shots

    CDC · https://www.cdc.gov/vaccines-children/before-during-after-shots/index.html

  2. Febrile Seizures and Vaccines

    CDC · https://www.cdc.gov/vaccine-safety/about/febrile-seizures.html

  3. When your baby or infant has a fever

    MedlinePlus · https://medlineplus.gov/ency/patientinstructions/000319.htm

  4. Babies and shots

    MedlinePlus · https://medlineplus.gov/ency/article/001967.htm

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.