Common Side Effects of Vaccines (& What to Do)

Clinical review: Manuel Reis
Registered Nurse
December 2022

Fever, headache, swelling or localized redness are the most common side effects of getting a vaccine, like the flu shot, COVID-19 injection or any other vaccines that are part of the normal immunization record. 

Side effects typically emerge in the first 48 hours after a vaccine, and are most common in children. Vaccines can often leave them irritated, agitated or tearful due to the discomfort associated with them. 

In most cases, symptoms are not serious and resolve within 3 to 7 days with just a few interventions that do not require a doctor visit. However, if a reaction starts to worsen or if you experience high levels of discomfort, you should proceed to the emergency room for assessment. 

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The most common side effects of vaccines (and what you can do) are as follows: 

1. Redness, swelling or pain in the area 

After an injection, the arm of leg can become very red, swollen and hard, resulting in pain with movement or palpation. These symptoms are common and are generally not a cause for concern, even if they cause some discomfort and limited movement for days. 

What to do: You can apply ice to the injection area for 15 minutes, 3 times per day, until symptoms disappear. The ice should be wrapped in a cloth to avoid direct contact with skin.

2. Fever or headache

A low grade fever can occur after an infection and can last for 2 or 3 days. Those who experience a fever will commonly also experience a headache, particularly on the day the vaccine was administered. 

What to do: A good way to relieve headache and fever naturally is to rest and place a cold, wet compress on your forehead. Learn about the other ways you can naturally treat a headache

You can also take antipyretics and analgesics, like acetaminophen, as advised by your doctor to relieve fever and headache quicker. These medications can be prescribed as syrup, drops, suppositories or pills, and dosing will depend on the doctor’s prescription. 

See ways you can break a fever at home using medication and other natural remedies. 

3. Fatigue, muscular pain and general malaise 

In the first 3 days after an infection, it is normal to feel unwell, as well as fatigue, muscular pain and drowsiness. In babies and children, the vaccine may cause increased bouts of crying and irritation, lack of interest in playing, drowsiness and reduced appetite. 

What to do: Rest and avoiding strenuous activity (like cleaning the house or working out) is advised. It is important to drink plenty of fluids throughout the day, like water, tea, natural juices or coconut water.  

4. Diarrhea, nausea or vomiting 

Gastrointestinal changes, like diarrhea, nausea or vomiting, are also relatively frequent, especially in children. These symptoms tend to resolve quickly, in about 2 or 3 days. 

What to do: You should eat light meals throughout the day to facilitate digestion, like vegetable soup, cooked fruit or white rice. You should drink lots of water to ensure adequate hydration. In babies, you should offer smaller amounts of milk or food to avoid indigestion. Learn more about what you can do to treat diarrhea

When to see the doctor 

When a fever lasts for more than 3 days or if the redness or pain in the injected area does not resolve within a week, you are advised to see your doctor. There may be other causes behind the symptoms that may require adequate treatment. 

In addition, when children do not eat appropriately for over 3 days, you should see the doctor to rule out other causes for a loss of appetite. 

In more serious cases, side effects from a vaccine can include difficulty breathing, facial swelling, intense itching or a lump in the throat. Any of these symptoms require immediate assessment in the emergency room, as they may indicate a serious allergy to a component in the vaccine.

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Edited by Tua Saude editing team in December 2022. Clinical review completed by Manuel Reis - Registered Nurse in December 2022.

References

  • NATIONAL IMMUNISATION PROGRAM. Following vaccination— what to expect and what to do. Available on: <https://www.health.gov.au/sites/default/files/doh_cimm_001_tear_off_pad_v19_accessible.pdf>. Access in 28 Jul 2021
  • SIEGRIST, C. A. Mechanisms underlying adverse reactions to vaccines. J Comp Pathol. 137. 1; S46-50, 2007
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  • VETTER, V.; et al. Understanding modern-day vaccines: what you need to know. Ann Med. 50. 2; 110-120, 2018
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Clinical review:
Manuel Reis
Registered Nurse
Manuel graduated in 2013 and is licensed to practice under the Ordem dos Enfermeiros de Portugal, with license #79026. He specializes in Advanced Clinical Phytotherapy.