Most of the adverse effects produced by vaccination are mild and transient and are limited to passing pain or swelling at the puncture site.
The cause of the adverse effects can be due to the vaccine itself, to the preservatives that are included to keep it stable, the antibiotics that are added at times to avoid its contamination or to other substances present in some vaccines.
The most serious adverse effects (anaphylactic reactions or encephalopathy) are very rare (approximately 1 case of every million vaccines put in) and, as previously explained, much less frequent than those produced by the disease we protect.
The most common side effects are:
Pain, swelling and redness at the puncture site. It is a relatively frequent and temporary reaction, which can be treated by the local application of a cold compress. If the pain is important, an analgesic such as paracetamol or ibuprofen can be used.
The appearance of a small hard lump at the puncture site. It occurs mainly after vaccination against whooping cough and meningitis B. They can be painful if we squeeze them with our hands. It disappears spontaneously after weeks.
Fever. Almost any vaccine preparation can produce fever after its administration, but it occurs more frequently after vaccination with triple viral (measles-rubella-mumps), the vaccine against meningococcus B and after vaccination with DTP (diphtheria-tetanus-pertussis) ) although the introduction of new vaccines against whooping cough (DTaP) has made this reactionless frequent. In the case of MMR vaccination, the fever usually appears several days after the vaccination (4 to 15 days later). If fever develops after vaccination, an antipyretic drug (paracetamol or ibuprofen) may be administered to the child and consult with your pediatrician in case the fever lasts more than 24-48 hours or other symptoms appear that are alarming or worry.