What are the risks associated with MMR (Measles, Mumps, and Rubella) and polio vaccines?

Risks of MMR and Polio Vaccines: Evidence-Based Analysis

The MMR and polio vaccines have extremely favorable safety profiles with rare serious adverse events, and their benefits in preventing potentially deadly diseases far outweigh their minimal risks.

MMR Vaccine Risks

Legitimate Risks (Evidence-Based)

• Febrile Seizures: The most well-documented risk is febrile seizures, occurring in approximately 1 in 2,300-2,600 children after the first dose of MMRV (combined MMR and varicella) vaccine 1. This risk is lower with separate MMR and varicella vaccines.

  • 97% of febrile seizures occur in children ≤47 months of age 2
  • Febrile seizures generally have excellent prognosis with no long-term sequelae 2

• Idiopathic Thrombocytopenic Purpura (ITP): Evidence supports an association between MMR vaccination and ITP, but the risk is much smaller than after natural infection 3

  • Attributable risk: approximately 1 case per 40,000 administered MMR doses
  • Natural infection ITP rate: 5 cases per 100,000 (1 per 20,000) per year

• Fever and Rash: Common minor reactions include:

  • Fever (≥102°F/39°C): Occurs in 14.9% of children receiving MMR 2
  • Measles-like rash: Occurs in 2.1% of children receiving MMR 2
  • These reactions typically occur 5-12 days post-vaccination and resolve spontaneously

Unfounded Claims (Not Evidence-Based)

• Autism: Multiple high-quality studies show no association between MMR vaccination and autism spectrum disorders (rate ratio 0.93,95% CI 0.85 to 1.01) 3

• Inflammatory Bowel Disease: Insufficient evidence to establish an association (odds ratio 1.42,95% CI 0.93 to 2.16) 3

• Encephalitis/Encephalopathy: No evidence of association (rate ratio 0.90,95% CI 0.50 to 1.61) 3

Polio Vaccine Risks

Legitimate Risks (Evidence-Based)

• Inactivated Polio Vaccine (IPV):

  • Very safe with minimal side effects
  • Minor local reactions at injection site may occur
  • No risk of vaccine-associated paralytic poliomyelitis

• Oral Polio Vaccine (OPV):

  • Associated with vaccine-associated paralytic poliomyelitis (VAPP), particularly in immunocompromised individuals 2
  • Due to this risk, OPV was discontinued in the United States in 2000 2
  • OPV continues to be used in developing countries due to ease of administration and effectiveness in eliminating wildtype virus 2

• SLE Flares: A retrospective study found that 5% (4/73) of patients with systemic lupus erythematosus developed disease flares after polio vaccination (1/24 after oral vaccine, 3/49 after inactivated vaccine) 2

Contraindications and Precautions

MMR Vaccine Contraindications 2:

• History of anaphylactic reaction to neomycin
• Allergic reaction to gelatin or other vaccine components
• Altered immunity or immunodeficiency
• Systemic immunosuppressive therapy
• Pregnancy

MMR Vaccine Precautions 2:

• Recent receipt of antibody-containing blood products
• History of thrombocytopenia
• Moderate or severe acute illness
• Personal or family history of seizures

Polio Vaccine (IPV) Contraindications:

• Severe allergic reaction to previous dose or vaccine component
• Moderate or severe acute illness

Sources of Arguments Against Vaccination

Scientific/Medical Community:

• Legitimate concerns focus on specific contraindications for special populations (immunocompromised individuals, those with history of specific allergic reactions)
• Medical literature acknowledges rare but real side effects while emphasizing overwhelming benefits

Non-Scientific Sources:

• Misinterpretation of temporal associations (events occurring after vaccination that are not causally related)
• Discredited studies (like the retracted 1998 Wakefield paper linking MMR to autism)
• Conspiracy theories lacking scientific evidence
• Anecdotal reports amplified through social media

Risk-Benefit Assessment

The scientific consensus strongly supports vaccination:

• MMR vaccine effectiveness is 95% after one dose and 96% after two doses in preventing measles 3
• Polio vaccines have nearly eradicated a devastating disease globally
• Natural infections carry far greater risks than vaccines:
  • Measles can cause encephalitis and pneumonia (major fatal complications) 2
  • Mumps can cause meningitis, encephalitis, and orchitis 2
  • Rubella causes miscarriages and devastating birth defects 2
  • Polio can cause permanent paralysis and death

The benefit-risk ratio overwhelmingly favors vaccination, with serious adverse events being extremely rare compared to the substantial protection provided against potentially deadly diseases.