Persistent Low-Grade Fever After Vaccination: What You Need to Know

Elevated body temperature?

Hello Doctor, I received the BNT vaccine on November 25th, and for the past three weeks, my body temperature has been consistently elevated.
I have been measuring my ear temperature (inserting the thermometer as deeply as possible) and it ranges from approximately 37.2 to 37.5 degrees Celsius, occasionally reaching 37.6.
After my menstrual period, my temperature remains the same, but in cooler environments, it sometimes drops to between 36.8 and 37.1.
I have visited the hospital for blood and urine tests, and all results were normal (including white blood cells, red blood cells, ESR, and HSCRP).
The only abnormal finding was 6-10 epithelial cells in my urine, but other urine tests were normal.
In October, I also underwent autoimmune testing, and my ANA was 1:80 (positive), but the doctor said it was normal.
The Anti-ENA (La-Ab) and Anti-ENA (Ro)-Ab levels were also normal.
I have not been regularly monitoring my temperature in the past, but when I did, it was around 36.6 to 36.8 degrees Celsius.
I would like to ask the doctor: 1.
Is my current temperature (ear temperature of 37.2-37.5) considered normal, slightly elevated, or indicative of a low-grade fever? 2.
Do I need to undergo any additional tests? 3.
If my temperature continues to remain elevated, could it be concerning, and how can I improve this? (I am currently drinking plenty of water.) I am really worried that it could be a serious illness or even a tumor.
Thank you, Doctor, for taking the time to respond.

Miss Huang, 20~29 year old female. Ask Date: 2021/12/16

Dr. Liao Zhongxin reply Internal Medicine

1.
Women's body temperature is indeed relatively higher during menstruation, while it tends to be lower at other times.
2.
Generally, a person's body temperature can fluctuate throughout the day; for example, it is lowest in the morning upon waking and tends to be highest in the late afternoon.
Therefore, it is recommended to measure and record your temperature at the same time each day for greater accuracy.
3.
Similar to blood pressure monitors, some thermometers also require regular calibration.
4.
If the above points 1-3 have been ruled out, consider visiting a hospital or laboratory for further examination; if abnormalities are found, it is advisable to consult the relevant specialty for further evaluation and treatment.

Reply Date: 2021/12/16

More Info

After receiving vaccinations, it is not uncommon for individuals to experience a low-grade fever as part of their immune response. In your case, you mentioned that you received the BNT vaccine on November 25, and now, over three weeks later, you are experiencing a persistent low-grade fever with ear temperatures ranging from 37.2°C to 37.5°C, occasionally reaching 37.6°C.
1. Understanding Your Temperature:
The temperatures you are reporting (37.2°C to 37.5°C) are considered low-grade fevers. Normal body temperature typically ranges from 36.1°C to 37.2°C. A temperature above 37.5°C can be classified as a low-grade fever. Therefore, your current readings do indicate a slight elevation in temperature, but they are not alarmingly high. It is essential to consider that body temperature can fluctuate throughout the day due to various factors, including activity level, time of day, and even the environment.

2. Further Investigations:
Given that you have already undergone blood and urine tests, which returned normal results (including white blood cell count, red blood cell count, ESR, and HSCRP), it suggests that there is no acute infection or significant inflammatory process occurring. The presence of a few epithelial cells in your urine is generally not concerning unless accompanied by other symptoms. If your symptoms persist or worsen, or if you develop new symptoms such as significant fatigue, weight loss, or night sweats, further investigations may be warranted. This could include imaging studies or more specialized blood tests to rule out any underlying conditions.

3. Managing Persistent Low-Grade Fever:
It is understandable to be concerned about persistent low-grade fever, especially with fears of serious underlying conditions. However, it is essential to remember that low-grade fevers can be a normal response to vaccinations as your immune system is activated. Staying hydrated, as you mentioned you are doing, is crucial. Additionally, monitoring your temperature regularly and keeping a record can help you and your healthcare provider assess any changes over time.

If your fever persists beyond a few weeks or if you experience any alarming symptoms, it would be advisable to consult with a healthcare professional. They may consider additional tests or referrals to specialists if necessary.
4. When to Seek Medical Attention:
If your fever continues for more than a few weeks without any signs of improvement, or if you develop new symptoms such as severe headaches, persistent fatigue, or any other unusual signs, it is essential to seek medical advice. It is also crucial to remain vigilant for any signs of systemic illness, such as significant weight loss, changes in appetite, or night sweats, which would warrant further evaluation.

In summary, while your current low-grade fever may be a normal response to the BNT vaccine, ongoing monitoring and communication with your healthcare provider are essential. If you have any concerns or if your symptoms change, do not hesitate to seek medical advice. Your health and peace of mind are paramount, and addressing any worries early can help ensure that you receive appropriate care.

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