Vaccine Adverse Events


Adverse events after immunization may be a true vaccine-associated event or may be a coincidental event that would happen without immunization. Epidemiologic studies are important to establish causation.


  • A clinically significant event that occurs after administration of a vaccine and has been causally related to the vaccine
  • All suspected adverse events should be reported; however, reporting does not imply causation.
  • Contraindication to immunization = condition that increases risk of a serious adverse reaction
  • Precaution for immunization = condition that might increase risk of an adverse event or may decrease effectiveness of vaccine to generate an immune response
    • Usually a temporary condition
    • Immunization indicated with a precaution if benefits outweigh risk


Adverse events monitored prelicensure to establish safety and postlicensure to identify rare adverse events that would not be detected in prelicensure studies. Reporting is guided by:

  • National Vaccine Injury Compensation Program:
    • Established by National Childhood Vaccine Injury Act of 1986 to establish a no-fault mechanism to manage claims of vaccine injury outside of the civil law system and provide compensation
    • Petitioners can file claims based on the Vaccine Injury Table (see “Patient Education”) created by the program or can attempt to prove causation for an injury that is not listed.
    • Covers vaccines recommended for routine administration to children
    • Program also mandates reporting of adverse events by health care professionals and creation of vaccine information materials.
  • Vaccine Adverse Event Reporting System (VAERS)
    • Passive surveillance system to monitor all vaccines licensed in the United States
    • All reports reviewed by U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) medical officers
    • Can detect possible unrecognized adverse events but unable to determine true causal relationships
    • Health care providers, vaccine recipients, or vaccine manufacturers can submit a report to VAERS.
  • Vaccine Safety Datalink
    • Active surveillance system formed by CDC in partnership with managed care organizations covering 9 million people
    • Can perform better observational studies to help determine causation
  • Clinical Immunization Safety Assessment Network
    • Network of six academic centers established by CDC in 2001 to develop research protocols to diagnose, evaluate, and manage adverse events
    • Develops evidence-based guidelines for immunizing people at risk for serious adverse events after vaccination
  • Post-licensure Rapid Immunization Safety Monitoring (PRISM) program
    • Established in 2009 by the FDA to monitor safety of pandemic influenza vaccine
    • Links electronic health record data to data from nine state immunization registries


  • Difficult to measure incidence owing to current reporting systems for adverse events
  • There are ~30,000 reports each year to VAERS.
    • 13% are considered serious adverse events.
  • Between 2006 to 2014, 3,451 petitions were reviewed by the National Vaccine Injury Compensation Program and 2,199 were compensated.


  • Common mild adverse events after vaccination include:
    • Fever
    • Local erythema, swelling, and/or tenderness
    • Sleepiness and decreased appetite
    • Increased fussiness
    • Mild rash: occurs in 1 of 25 people up to 1 month after varicella vaccination
  • Moderate to serious adverse events to currently recommended vaccines are rare but include:
    • Syncope, particularly among adolescents
    • Febrile seizures (measles, mumps, rubella [MMR], varicella, and diphtheria-tetanus-acellular pertussis [DtaP] vaccines)
    • Temporary joint pain or stiffness (MMR)
    • Temporary thrombocytopenia (MMR)
    • High fever
    • Shoulder injury related to vaccination
  • To minimize the possibility of vaccine adverse events and to maximize the effectiveness of vaccination, the following contraindications and precautions, listed below, should be followed.

Differential Diagnosis

  • Allergic reaction to an unrelated exposure
  • Intercurrent illness

Ongoing Care

  • Approach
    • Before vaccination:
      • Discuss benefits and potential known adverse events so that families know what to expect.
      • Actively review vaccine information sheets.
      • Solicit concerns that they can be addressed.
      • Review medical history for conditions that are contraindications or precautions for vaccination.
  • Contraindications
    • General contraindications for vaccination include:
      • History of an anaphylactic reaction to a vaccine component:
        • History of egg allergy no longer contraindication to influenza vaccination unless documented history of anaphylactic reaction
      • Pregnancy for live-virus vaccines unless mother is at high risk for the vaccine-preventable condition
      • Primary T-cell immunodeficiencies (i.e., severe combined immunodeficiency [SCID]):
        • No live vaccines
        • Inactivated vaccines can be safely administered but may not generate an adequate immune response.
      • Primary B-cell immunodeficiencies:
        • If severe (i.e., X-linked agammaglobulinemia), no live bacterial vaccines, live-attenuated influenza vaccine (LAIV), or yellow fever vaccine
        • Less severe antibody deficiencies can receive live vaccines except for OPV.
      • Phagocyte dysfunction:
        • No live bacterial vaccines
        • All live-virus and inactivated vaccines probably safe and effective
      • Secondary immunosuppression (transplant, malignancy, autoimmune disease):
        • No live vaccines depending on degree of immunosuppression
        • Can achieve adequate response to vaccination within 3 months to 2 years after stopping immunosuppressive therapy
      • HIV/AIDS:
        • Can give MMR and varicella vaccine unless severely immunocompromised
        • No OPV or LAIV
      • High-dose corticosteroids >14 days:
        • No live-virus vaccines until therapy discontinued for at least 1 month
      • Vaccine-specific contraindications
        • DTaP/Tdap
          • Encephalopathy within 7 days of previous DTP, DTaP, or Tdap dose not attributable to another cause
        • Rotavirus
          • SCID
          • Previous history intussusception
        • Hib conjugate vaccine should not be given to infants <6 weeks of age.
        • LAIV: Advisory Committee on Immunization Practices recommends against use in multiple groups (please see “Influenza” chapter).
  • Precautions
    • General precautions for receiving a vaccine include moderate to severe acute illness with or without fever. Vaccine-specific precautions include:
      • DTaP/DTP
        • Fever ≥104°F or shock-like state within 48 hours of previous DTaP/DTP dose
        • Persistent, inconsolable crying >3 hours within 48 hours of previous DTaP/DTP dose
        • Seizure within 3 days of previous DTaP/DTP dose
      • Any tetanus toxoid–containing vaccine:
        • Guillain-Barré within 6 weeks of a previous tetanus toxoid–containing vaccine dose
        • Progressive neurologic disorder (infantile spasms, poorly controlled epilepsy)
        • History of Arthus hypersensitivity reaction after previous tetanus toxoid–containing dose
          • Wait 10 years between doses of tetanus toxoid–containing vaccines.
      • Inactivated influenza vaccines (IIVs)
        • History of Guillain-Barré within 6 weeks of a previous dose of influenza vaccine
        • Egg allergy other than hives (angioedema, respiratory distress, emesis)
          • May receive IIV in an outpatient or inpatient medical setting under supervision of a health care provider who can manage severe allergic reactions
      • Human papillomavirus (HPV) vaccines:
        • Pregnancy
      • Varicella:
        • Receipt of antibody-containing blood product within past 11 months
        • Immunocompromised household contacts are not a contraindication or precaution, but if rash develops 7 to 25 days after vaccination, should avoid direct contact with immunocompromised individual.
        • Receipt of certain antiviral drugs within 24 hours before vaccination
      • MMR:
        • Receipt of antibody-containing blood product within past 11 months
        • History of thrombocytopenic purpura
        • Need for tuberculin skin test or interferon-γ release assay (IGRA) testing
      • Rotavirus:
        • Immunosuppression (other than SCID)
        • Chronic gastrointestinal disease
        • Spina bifida or bladder exstrophy
      • The following are NOT precautions or contraindications to the receipt of any vaccine:
        • Mild or recent illness
        • History of a mild to moderate local reaction to vaccine in the past
        • Concurrent antimicrobial therapy
        • Breastfeeding
        • History of other nonvaccine allergies
        • Stable neurologic conditions (e.g., cerebral palsy, developmental delay)
      • For all precautions, decision to give vaccine based on assessment of benefits versus risks of vaccination
  • Management
    • If a patient presents with a potential adverse event:
      • Take thorough history and perform exam to characterize symptoms and determine timing of symptom onset.
      • Evaluate for other potential causes of symptoms.
      • Determine likelihood of causality.
      • Report all adverse events to VAERS.
      • If the family would like to file a claim, refer to National Vaccine Injury Compensation Program.
    • Addressing safety concerns:
      • Nearly 20% of parents from a national telephone survey refused or delayed at least one recommended vaccine.
      • Growing prevalence of misinformation about vaccines challenges provider–parent communication.
      • Despite increasing vaccine safety concerns, health care professionals are one of the most trusted sources of information regarding vaccines.
      • Provide tailored information emphasizing benefits of vaccination and potential consequences of not accepting vaccination.
      • Actively solicit concerns before vaccination.
      • If parents have specific concerns, refer to additional information sources for reliable and accurate information (see references in “Patient Education”).
      • Document vaccine discussions.
    • Reporting adverse events:
      • VAERS is the primary reporting site for suspected adverse events. Health care providers, vaccine recipients, or parents of vaccine recipients and vaccine manufacturers can all report.
      • Health care providers are required to report:
        • Any adverse event listed by vaccine manufacturer as a contraindication for the receipt of additional doses of the vaccine
        • Any adverse event included on the VAERS table of reportable events that occurred within the specified time period
    • Vaccine Injury Compensation Program:
      • Covers all vaccines recommended for routine administration by the Advisory Committee on Immunization Practices
      • To qualify for compensation, must prove there was an injury listed in the Vaccine Injury Table that occurred within prescribed time period, prove that a vaccine caused an injury not listed on the table, or prove that a vaccine aggravated a preexisting condition
      • Burden of proof is based on “presumption of causation.”
      • Effects of injury must last >6 months after vaccination and have resulted in hospitalization, surgery, or death.

Patient Teaching

Additional Reading

  1. American Academy of Pediatrics. Active immunization. In: Kimberlin DW, ed. Red Book: Report of the Committee on Infectious Diseases. 30th ed. Washington, DC: American Academy of Pediatrics; 2015:43–56.
  2. American Academy of Pediatrics. Immunization in special clinical circumstances. In: Kimberlin DW, ed. Red Book: Report of the Committee on Infectious Diseases. 30th ed. Washington, DC: American Academy of Pediatrics; 2015:68–101.
  3. Cook KM, Evans G. The National Vaccine Injury Compensation Program. Pediatrics. 2011;127(Suppl 1):S74–S77.  [PMID:21502255]
  4. Edwards KM, Hackell JM; for Committee on Infectious Diseases, The Committee on Practice and Ambulatory Medicine. Countering Vaccine Hesitancy. Pediatrics. 2016;138(3):e20162146.  [PMID:27573088]
  5. Stratton K, Ford A, Rusch E, et al, eds Adverse Effects of Vaccines: Evidence and Causality. Washington, DC: The National Academies Press; 2012.
  6. Rubin LG, Levin MJ, Ljungman P, et al; for Infectious Diseases Society of America. 2013 IDSA clinical practice guideline for vaccination of the immunocompromised host. Clin Infect Dis. 2014;58(3):309–318.  [PMID:24421306]



  • 999.9 Other and unspecified complications of medical care, not elsewhere classified
  • 999.52 Other serum reaction due to vaccination
  • 999.42 Anaphylactic reaction due to vaccination
  • 999.39 Infection following other infusion, injection, transfusion, or vaccination


  • T88.1XXA Oth complications following immunization, NEC, init
  • T80.62XA Other serum reaction due to vaccination, initial encounter
  • T80.52XA Anaphylactic reaction due to vaccination, initial encounter
  • T88.0XXA Infection following immunization, initial encounter
  • M02.20 Postimmunization arthropathy, unspecified site


  • 293104008 vaccines adverse reaction (disorder)
  • 294640001 vaccines allergy (disorder)
  • 95371007 application site rash (disorder)
  • 23301003 Infection following infusion, injection, transfusion AND/OR vaccination (disorder)
  • 31935007 complication due to vaccination (disorder)
  • 417516000 Anaphylaxis due to substance (disorder)


  • Q: Many parents request spacing vaccines. Is there evidence that giving multiple vaccines at a time is too much for a child’s immune system?
  • A: Recommended vaccines have a very small amount of antigen compared to natural infection and they activate a small proportion of immune system memory. Additionally, all vaccines given together have been tested when given at the same time to make sure they remain safe and effective.
  • Q: What is the bottom line regarding autism and vaccines?
  • A: Multiple studies including a recent Institute of Medicine report have not shown any causal relationship between thimerosal-containing vaccines and autism or MMR and autism. Additionally, the U.S. court system through the Omnibus Autism Proceedings has recently ruled that there is insufficient evidence to show any causal relationship between thimerosal-containing vaccines or MMR and autism.


Kristen A. Feemster, MD, MPH, MSHP

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