What are the potential adverse effects of the MMR vaccine?

The live attenuated viruses of the MMR vaccine multiply in the body. They trigger resistance to measles, mumps and rubella. 

The potential risk of adverse effects caused by a vaccination should always be compared to the risk of the disease itself and its secondary diseases and complications.

The MMR diseases are significantly more severe than a potential mild infection caused by the vaccination. 

The MMR diseases may cause serious secondary diseases or complications. The risk of these secondary diseases or complications is tens of times greater, or even thousand-fold, compared to the risk caused by the vaccination.

Symptoms resembling MMR diseases

Between 5% and 15% of vaccine recipients develop mild symptoms resembling the MMR diseases, typically after the first vaccine dose. 

The symptoms appear within 5 to 12 days of the vaccination and usually disappear in a few days or a week. 

Common symptoms include

  • fever, cough, a runny nose or redness of eyes
  • a measles or rubella type rash
  • irritability, restlessness, headaches
  • mild joint aches
  • transient enlargement of lymph nodes.

The following have been described in very rare cases following the vaccination

  • swelling of the parotid gland
  • swelling of the testicles in individual cases.

Common symptoms resembling the diseases are not a contraindication to further vaccinations. Adverse effects are usually no longer observed after the second dose.

Joint inflammation symptoms are rare, especially in children. A certain rubella virus strain linked to cases of joint inflammation is no longer used in today’s MMR vaccines.

Measles or mumps are associated with a significant risk of meningitis or encephalitis. Severe neurological complications are extremely rare in those who have been vaccinated.

Convulsions are usually observed in connection with fever caused by the vaccination. However, the risk of convulsions associated with the actual disease is considerably higher.

Thrombocytopenia, or low platelet count

A reduced platelet count causes subcutaneous bruising or bleeding. 

Thrombocytopenia associated with the MMR vaccine is rare and usually requires no treatment. In studies, its incidence following an MMR vaccination has been 1 case per 50,000 recipients.

The risk of thrombocytopenia following a vaccination is significantly lower than this risk in those who have contracted measles or rubella. In many cases, thrombocytopenia may have been caused by some other infection that the child has had simultaneously.

Allergic reactions

Allergic reactions, including anaphylaxis, are extremely rare after an MMR vaccination.
Contraindications and precautions associated with the MMR vaccine

No link between autism and the MMR vaccine

The MMR vaccine has not been found to cause autism. In 1998, a British scientist came forward with a theory linking the MMR vaccine to autism. Their study comprised the data of eight children in total. 

Since then, the role of vaccinations in the causation of autism has been examined in extensive national and international studies.  

The findings show that vaccinations and autism are two separate incidents that happen to occur at the same age. 

In many countries, the first MMR vaccine is administered to children at the age of 12 to 18 months, the age at which the first symptoms of autism are usually also noticed. 

However, changes indicating autism can already be found in the brains of children aged 6 to 12 months. The mechanisms that cause autism are not yet fully known.