Vaccine Safety

Vaccines have saved millions of lives, especially the lives of children, who used to die in great numbers or be seriously debilitated due to many childhood diseases, such as measles and polio. Very few children have reactions from childhood vaccines, and most are minor, such as a mild fever or redness around the area of the vaccination. It is nonetheless very important to track any potential very rare and serious side effects. For this, the CDC has developed the Vaccine Adverse Event Reporting System (VAERS). 

VAERS was established in 1990 through a collaborative effort between the Centers for Disease Control (CDC) and the U.S. Food and Drug Administration (FDA). VAERS allows healthcare providers, vaccine manufacturers, and members of the public to submit reports of adverse events that follow vaccination. Correlation does not automatically prove causation – an event that follows a vaccine may have nothing to do with the vaccine. However, by collecting this information, the CDC and FDA are able to monitor adverse events (AE) and determine if there are any red flags that indicate the need for further research. 

Reported AE can range from redness and fatigue to the five serious adverse outcomes that trigger immediate investigation:

  • Death
  • Life-threatening AE
  • Inpatient hospitalization or extension of existing hospitalization
  • Persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions
  • Congenital anomaly/birth defect

Reports of serious AE are followed up within five days. VAERS investigators generally contact the health facilities (at times the individuals, as well) for more detail related to the report. Often, reports are incomplete, and further information is necessary to carefully analyze the event.  Experts will use additional safety systems, such as the CDC’s Vaccine Safety Datalink and Clinical Immunization Safety Assessment Project, or the FDA’s Biologics Effectiveness and Safety system and data obtained in collaboration with the Centers for Medicare & Medicaid Services. The occurrence of the AE will also be compared with the occurrence of the same condition in people who have not had the vaccine. Deeper analysis will determine if the event occurs more or less often in certain populations, depending on male or female, age, race, location, and frequency or timing of dosage. 

Discovery of any risks related to a vaccine in any particular population may lead to a pause or an adjustment in recommendations regarding the administration of the vaccine. 

BCHIP is a collaboration between medical facilities and health agencies in Bucks County, and we take our responsibility for your health and well-being very seriously. If you have any concerns about your health or the health of your child following a vaccine, even if the event occurs several weeks following the vaccine, contact your medical health provider immediately. He or she will be able to evaluate you, provide you with any medical help or advice you need, and determine whether or not to report your event to VAERS. You may also report to VAERS yourself, at


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