Fever and Headache After Vaccination: When to Seek Medical Help?

Fever and headache after receiving the varicella vaccine, MMR vaccine, influenza vaccine, and adult Tdap vaccine?

Hello: About 15 days ago, I received the varicella vaccine, MMR vaccine, influenza vaccine, and adult Tdap vaccine.
Two days ago, I started experiencing fever and headache.
I have taken Tylenol, which contains 500 mg of acetaminophen, and so far, I have taken a total of 4 tablets.
Whenever I take it, the fever subsides and I sweat, but after about 6 hours, my temperature rises again to 37.5–38 degrees Celsius (ear temperature).
The headache improves slightly with medication, and I have some mild neck stiffness but can turn my head freely.
I noticed that when I look up, to the right, or to the left, I experience a pulling pain in the back of my head.
I do not have any other specific symptoms, no blurred vision, photophobia, red eyes, or vision loss.
Since I am currently studying abroad, and due to the severe pandemic situation, it is inconvenient to seek medical care.
I would like to ask the doctor: 1.
Is it possible to develop a low-grade fever 13 days after receiving the aforementioned vaccines? If so, which vaccine could be responsible? 2.
Is it necessary to seek medical attention in this situation? What new symptoms would warrant a visit to the doctor? 3.
If medical attention is not needed, how long might this fever last, and under what circumstances should I take antipyretics? 4.
If the fever persists, on which day should I seek medical care? Thank you for your assistance.

rg, 30~39 year old female. Ask Date: 2021/12/17

Dr. Ye Qianyu reply Family Medicine

Hello! After vaccination, the timing of fever for the varicella vaccine and the measles, mumps, and rubella (MMR) vaccine typically occurs about 5 to 12 days post-vaccination, while for other vaccines, it usually occurs around 8 to 12 hours after administration.
Vaccine-related fevers are generally low-grade, with temperatures ranging from 37.5 to 38.5 degrees Celsius, and rarely exceeding 39 degrees Celsius.
The duration of the fever is usually no longer than 24 hours.
Based on your description, it seems that it has been more than two weeks.
If your fever persists for more than 3 days and is accompanied by other symptoms, it may indicate an infection rather than being solely caused by the vaccination.
If you are in an area with a high prevalence of COVID-19, you may consider performing a home rapid test.
If you experience severe symptoms such as difficulty breathing or dehydration, please seek medical attention promptly.

Reply Date: 2021/12/17

More Info

After receiving multiple vaccinations, including the varicella (chickenpox) vaccine, MMR (measles, mumps, rubella) vaccine, flu vaccine, and Tdap (tetanus, diphtheria, pertussis) vaccine, it is not uncommon to experience mild side effects such as fever and headache. These reactions are generally a sign that your immune system is responding to the vaccines.
1. Is it possible to have a low-grade fever 13 days after vaccination? Which vaccine could cause this?
Yes, it is possible to experience a low-grade fever 13 days after vaccination, particularly with the varicella and MMR vaccines. The MMR vaccine can cause fever about 5 to 12 days after administration, while the varicella vaccine can also lead to mild fever within a similar timeframe. The flu vaccine typically causes side effects within 8 to 12 hours post-vaccination, and the Tdap vaccine may cause reactions within a day or two. Given that your symptoms began two days ago, it is plausible that they are related to the MMR or varicella vaccines.

2. Do you need to seek medical attention for these symptoms? What new symptoms would warrant a visit?
If your fever remains low-grade (below 39°C or 102°F) and is manageable with acetaminophen (Tylenol), and you do not have any alarming symptoms, it may not be necessary to seek medical attention. However, you should monitor for new symptoms such as:
- A high fever (above 39°C or 102°F) that persists for more than 3 days.

- Severe headache that does not improve with over-the-counter pain relief.

- Stiff neck or severe neck pain.

- Confusion, difficulty waking, or seizures.

- Shortness of breath or chest pain.

- Any signs of an allergic reaction, such as difficulty breathing, swelling of the face or throat, or hives.

3. If you do not need to see a doctor, how long might the fever last, and when should you take fever-reducing medication?
Vaccine-related fevers typically resolve within 24 to 48 hours. If your fever persists beyond three days or if it rises significantly, you should consider taking acetaminophen to manage your symptoms. It is advisable to take fever-reducing medication if your fever exceeds 38°C (100.4°F) and is causing discomfort. Always follow the dosing instructions on the medication label and consult a healthcare professional if you have any concerns about medication interactions, especially since you are studying abroad and may have limited access to healthcare.

4. If the fever continues, when should you seek medical help?
If your fever persists for more than three days, or if you develop any of the concerning symptoms mentioned earlier, you should seek medical attention. It is crucial to err on the side of caution, especially in the context of the ongoing pandemic, where respiratory illnesses may present similarly to vaccine side effects.

In summary, while mild fever and headache can be common after vaccinations, it is essential to monitor your symptoms closely. If you experience any concerning changes or if your symptoms do not improve, do not hesitate to seek medical advice. Your health and well-being are paramount, and timely intervention can help address any potential complications.

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