Vaccination, or immunization, remain one of the most effective ways to prevent infectious diseases. According to the World Health Organization (WHO), vaccinations prevent between 2 and 3 million deaths worldwide each year. However, many people still have concerns about the possible effects and reactions that accompany vaccine administration. What symptoms are considered normal and when should you seek medical attention?
Why do I have a reaction to a vaccination?
Vaccines contain weakened or inactivated (killed) pathogens or their fragments. When they enter the body, the immune system recognizes “foreign” elements, learns to produce antibodies and “remembers” their structure. In the next encounter with a living pathogen, the body will be ready to repel the attack.
Side effects or so-called postvaccinal reactions occur because the defense mechanisms are triggered quite actively. The immune system uses up resources and activates various cells, which can lead to local inflammatory reactions (redness, swelling, pain) or more general symptoms (fever, fatigue).
Normal reactions to the vaccination
1. Mild fever
A fever of 37.5-38.0 °C in the first 24 hours after vaccination is considered normal. This is the body’s way of indicating that the immune system has kicked in. According to the U.S. Centers for Disease Control and Prevention (CDC), a short fever after vaccination is one of the most common safe reactions.
2. Pain and redness at the injection site
A localized reaction may come in the form of mild soreness, thickening, or redness of the skin at the injection site. Most often these symptoms do not require any treatment and resolve on their own within a few days. It is only recommended to avoid excessive mechanical irritation of this area (e.g., strong pressure).
3. General weakness, malaise
Sometimes, on the day of vaccination or the next day, people may feel drowsy or have a slight weakness in the joints or muscles. This is a normal sign of immune activation. If these symptoms are mild and are not accompanied by fever or severe pain, it can be considered a safe reaction.
4. Mild allergic reaction
A small rash that sometimes appears on the skin and mild itching without swelling or palpitations may indicate a mild allergic reaction. Most often the symptoms will go away without medication, but if they get worse, it is best to see a doctor.
Signs of serious complications
- High fever (above 39 °C)
A sudden onset of fever accompanied by severe chills and headache may indicate a serious inflammatory reaction. If the fever persists or worsens overnight, a doctor should be consulted.
- Severe allergic reaction
Anaphylaxis, an acute allergic reaction that can be life-threatening, is extremely rare but possible. Severe shortness of breath, swelling of the face, tongue, neck, palpitations, rapid heartbeat, sudden drop in blood pressure are signs that require immediate medical attention.
- Seizures or loss of consciousness
If a person experiences seizures, fainting, or prolonged confusion after vaccination, urgent consultation with a medical professional is necessary to determine the true cause.
- Prolonged severe swelling and inflammation
If redness and swelling around the injection site increases after a few days, symptoms of bacterial inflammation (suppuration) may appear. In such cases, medical attention should be sought immediately, as antibiotic therapy may be required.
Recommendations for self-care after immunization
- Monitoring your well-being
During the first 24-48 hours after vaccination, it is important to monitor your temperature and general condition. If fever occurs, you can take antipyretics (in consultation with your doctor), and in case of severe pain – painkillers.
- Rest
On the first day after vaccination, give yourself some rest: avoid heavy physical exertion and try to sleep at least 7-8 hours. This will help the body to focus its energies on forming an immune response.
- Moderate drinking and diet
Drink enough water (tea, compote, pure water) to maintain water-salt balance. Refuse from excessively spicy or fatty food – it can additionally burden the body.
- Local care of the injection area
You can take a warm shower, but it is undesirable to rub or warm the injection site. If there is a slight induration, a mild gel or ointment is sufficient (in consultation with the doctor).
Mistakes and misconceptions about vaccination
- “A mild fever is always a complication.”
A slight fever within 24-48 hours after vaccine administration is a normal sign of immune activation. It doesn’t require panic and often goes away on its own.
- “If there was a side effect, you should refuse further immunizations.”
A mild allergic reaction, a lump at the injection site or malaise does not mean that you should cancel all subsequent vaccines. Your doctor can help you find an alternative medication or make recommendations on how to prepare for a second vaccination.
- “The vaccine causes the disease itself.”
The vaccine contains either weakened or “killed” pathogen material or a protein fragment that is incapable of causing the disease in its entirety. Soreness, fever and other symptoms do not mean that the infection has taken root. It is only a reaction of the body preparing to defend itself.
- “Vaccinations are unnecessary because many diseases are rare now”
Thanks to mass vaccination, some infections are indeed much rarer. But when collective immunity levels decline, these diseases can return. There are examples in history where measles and diphtheria outbreaks occurred when vaccinations were withheld.
Conclusion
Vaccinations play a key role in protecting against dangerous infections and preserving public health. Side effects after vaccination are in most cases a normal reaction of the body and go away without consequences. Serious complications are extremely rare and are usually recognized in time and treated successfully. It is important not to give in to fears and myths, but to rely on scientific data and doctors’ recommendations. An informed approach to vaccination is an investment in your own health and the safety of others.
