Persistent Fever After Third COVID Vaccine: When to Seek Medical Advice?

Fever lasting for a week after receiving the third dose of the COVID-19 vaccine, with a history of exposure to a confirmed case?

Hello, doctor.
I am a sixteen-year-old student.
Last Wednesday (June 8), I received my third dose of the BNT vaccine and had contact with a confirmed case on the same day (I was wearing a mask the entire time).
I did a rapid test at home a few days later, which was negative.
This week, my temperature has consistently been over 38 degrees Celsius.
After taking acetaminophen, it dropped to just above 37 degrees, but it quickly rose again.
I experienced muscle soreness for about three days (which I believe is a side effect of the vaccine), and in the last couple of days, I have had mild diarrhea.
I do not have a sore throat or nasal discomfort, nor have I experienced any loss of smell or taste; I am just experiencing persistent fever and fatigue.
Is it normal to have a fever for this long after vaccination, or should I seek medical attention? Thank you for your response!

Miss Chen, 10~19 year old female. Ask Date: 2022/06/15

Dr. Hong Yuanbin reply Internal Medicine

Hello, theoretically, it is possible to experience some discomfort within a week after vaccination; however, these symptoms, especially fever, rarely last more than a week.
If you continue to have a fever in the next few days, it is advisable to take a rapid test to rule out COVID-19 infection.
If the rapid test is negative and the fever persists, you should seek medical attention to determine if there are other issues.
You can visit a family medicine or infectious disease clinic.
Thank you for your question.

Reply Date: 2022/06/15

More Info

After receiving the third dose of the COVID-19 vaccine, it is not uncommon for individuals to experience side effects, including fever, muscle aches, and fatigue. These symptoms are generally a sign that your immune system is responding to the vaccine, which is designed to help your body build protection against the virus. However, persistent fever lasting more than a few days can be concerning and warrants careful consideration.

In your case, you mentioned experiencing a fever of over 38 degrees Celsius for a week, along with muscle pain and mild diarrhea. While mild fever and muscle soreness can be typical side effects following vaccination, especially after the third dose, a fever lasting this long is less common and should be evaluated further. The fact that you have tested negative for COVID-19 through rapid testing is reassuring, but it does not completely rule out the possibility of other infections or complications.

Here are some key points to consider regarding your symptoms:
1. Duration of Symptoms: While mild fever and other side effects can last for a few days post-vaccination, a fever persisting for more than a week is unusual. It is essential to monitor the fever closely. If it continues beyond a week or worsens, seeking medical advice is advisable.

2. Associated Symptoms: You mentioned experiencing muscle aches and mild diarrhea. While these can be side effects of the vaccine, the combination of persistent fever and these symptoms could indicate another underlying issue, such as a viral or bacterial infection unrelated to the vaccine.

3. COVID-19 Exposure: Given that you were in contact with a confirmed COVID-19 case, it is crucial to remain vigilant. Although your rapid tests have been negative, it may be worth considering a PCR test, as it is more sensitive and can detect the virus even when rapid tests do not.

4. Hydration and Rest: Ensure you are staying well-hydrated and getting plenty of rest. Over-the-counter medications like acetaminophen (Tylenol) can help manage fever and discomfort, but if the fever persists despite medication, it is a sign that you should consult a healthcare provider.

5. When to Seek Medical Attention: If your fever continues, if you develop new symptoms (such as difficulty breathing, chest pain, severe headache, or rash), or if you feel significantly more fatigued than usual, it is essential to seek medical attention. A healthcare professional can perform a thorough evaluation, which may include blood tests or imaging studies, to determine the cause of your symptoms.

In summary, while some degree of fever and discomfort can be expected after vaccination, persistent fever for a week is not typical and should be evaluated by a healthcare professional. It is always better to err on the side of caution, especially considering your recent exposure to a confirmed case of COVID-19. Your health and well-being are paramount, and a medical professional can provide the necessary guidance and care.

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