Persistent Elevated Body Temperature After COVID-19 Vaccination: What to Know

Elevated body temperature?

Hello Doctor, I received the AZ vaccine a month ago, and it has been over 5 weeks now.
My daytime temperature (ear temperature) is around 37.1 degrees Celsius, and during the warmer hours from noon to afternoon, it can reach 37.3 degrees.
When I exercise, it goes up to 37.6 degrees, but after resting, it usually drops back to 37.2 degrees.
In the evening, my ear temperature decreases slightly to 36.9 degrees.
Two weeks after the vaccination, I experienced elevated temperatures and dizziness, which led me to visit the emergency room twice; blood tests, urinalysis, and X-rays all came back normal.
Four weeks later, I had blood tests related to my immune system at the immunology department, and all values were normal.
Now, over 5 weeks have passed, and I have no other discomfort and my appetite is normal, but my temperature has not returned to the previous normal level (around 36.5 degrees).
I feel quite helpless and a bit anxious.
Should I undergo any further tests? Thank you.

lai, 30~39 year old female. Ask Date: 2021/09/13

Dr. Xiao Yongxun reply Family Medicine

Dear Ms.
Lai,
1.
The reactions that may occur after receiving the AstraZeneca vaccine are mostly pain and swelling at the injection site, which typically resolve within a few days.
You may apply a cold compress, but please do not rub or scratch the injection site.
Fever (≥38°C) may occur after vaccination, usually subsiding within about 48 hours.
Other possible reactions include fatigue, headache, muscle pain, elevated body temperature, chills, joint pain, and nausea.
These symptoms tend to decrease with increasing age and are generally mild, resolving within a few days.
If you experience redness, swelling, and a hard lump at the injection site that develops into an abscess, persistent fever, or severe allergic reactions (such as difficulty breathing, wheezing, dizziness, rapid heartbeat, or widespread rash), seek medical attention promptly and inform your physician that you have received the vaccine for diagnostic reference.
Within 28 days post-vaccination, if you experience severe persistent headache, changes in vision or seizures, severe and persistent abdominal pain lasting more than 24 hours, severe chest pain or difficulty breathing, swelling or pain in the lower limbs, or spontaneous skin bleeding, bruising, or purpura, please seek immediate medical care and provide your vaccination history.
2.
Regarding your description, while it cannot be completely ruled out that the elevated body temperature is caused by the AstraZeneca vaccine, the likelihood is low.
I personally recommend that you drink plenty of warm water and consume an adequate amount of fruits daily to reduce immune inflammatory responses; it may normalize in a few days.
If the elevated temperature persists, I encourage you to discuss with your primary care physician whether there may be other underlying causes, rather than attributing it solely to the vaccine.
Of course, you may also directly consult an infectious disease specialist at a regional hospital for further clarification.

Reply Date: 2021/09/13

More Info

After receiving the AstraZeneca (AZ) COVID-19 vaccine, it is not uncommon for individuals to experience a range of side effects, including a mild elevation in body temperature. This is a normal immune response as your body builds protection against the virus. In your case, it has been over five weeks since vaccination, and you are still experiencing a slightly elevated body temperature, which can understandably cause concern.

Firstly, it is important to note that a body temperature ranging from 37.1°C to 37.6°C can be considered within the normal range for some individuals, especially if this is close to your baseline temperature. Body temperature can fluctuate throughout the day due to various factors, including physical activity, time of day, and even hormonal changes. For example, it is common for body temperature to be lower in the morning and higher in the late afternoon and evening.

Given that you have already sought medical attention twice and undergone various tests—including blood tests, urine tests, and X-rays—all of which returned normal results, this is a positive indication that there is no acute underlying condition that requires immediate intervention. Additionally, your follow-up with an immunologist, which also yielded normal results, suggests that your immune response is functioning appropriately.

Persistent mild fever or elevated body temperature can sometimes occur after vaccination and may last for several weeks. This phenomenon is often referred to as "post-vaccination syndrome," where the immune system remains slightly activated as it continues to respond to the vaccine. In most cases, this is self-limiting and resolves on its own without the need for further medical intervention.

However, it is essential to monitor your symptoms closely. If you experience any new symptoms such as severe headaches, persistent dizziness, difficulty breathing, chest pain, or any other concerning signs, it would be prudent to seek medical attention promptly. Additionally, if your elevated temperature persists beyond a few more weeks or if you find it increasingly bothersome, discussing further evaluations with your healthcare provider may be warranted. They might consider additional tests to rule out other potential causes, such as autoimmune conditions or infections that may not have been evident in initial screenings.

In the meantime, managing your anxiety about this situation is crucial. Stress and anxiety can sometimes exacerbate physical symptoms, including the perception of fever. Engaging in relaxation techniques, maintaining a healthy diet, staying hydrated, and ensuring adequate rest can help support your overall well-being during this time.

In summary, while it is understandable to feel anxious about persistent mild fever after vaccination, your current situation appears to be within the realm of normal post-vaccination responses. Continue to monitor your health, maintain open communication with your healthcare provider, and seek further evaluation if your symptoms change or worsen.

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