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Data source: VAERS (Vaccine Adverse Event Reporting System)

Data through 2026 · Updated quarterly

Built by TheDataProject.ai · © 2026 VaccineWatch

Important: VAERS accepts reports of adverse events following vaccination. For any given report, there is no certainty that the reported event was caused by the vaccine. Reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. Most reports to VAERS are voluntary, which means they are subject to biases. This data cannot be used to determine if vaccines cause or contribute to adverse events.

⚠️

Important: VAERS reports alone cannot determine if a vaccine caused an adverse event. Reports may contain incomplete, inaccurate, or unverified information. Correlation does not equal causation.

  1. Home
  2. Vaccine Side Effects
  3. MMR Vaccine
7 min read
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MMR Vaccine Side Effects

The MMR (measles, mumps, rubella) vaccine is one of the most widely studied vaccines in history. Given to virtually every child in the U.S., it generates a substantial number of VAERS reports — but context is essential for interpreting this data.

113,538
Total Reports
542
Deaths Reported
5,685
Hospitalizations
36,986
ER Visits

Most Commonly Reported Side Effects

The following symptoms are most frequently reported after vaccination:

#{i + 1}Pyrexia
23,873
#{i + 1}Rash
13,811
#{i + 1}Injection site erythema
12,059
#{i + 1}No adverse event
8,580
#{i + 1}Erythema
6,579
#{i + 1}Injection site swelling
6,533
#{i + 1}Urticaria
5,891
#{i + 1}Pruritus
5,176
#{i + 1}Injection site oedema
4,926
#{i + 1}Injection site warmth
4,639
#{i + 1}Vomiting
4,559
#{i + 1}Injection site pain
4,541

MMR and Autism: The Data

The claimed link between MMR and autism has been extensively studied and debunked. The original 1998 study was retracted and its author lost his medical license for fraud. Multiple large-scale studies involving millions of children have found no connection between MMR vaccination and autism.

VAERS does contain reports mentioning autism after MMR vaccination, but VAERS reports are unverified and cannot establish causation. The timing of MMR vaccination (12-15 months) coincides with when autism symptoms typically become noticeable, creating a temporal correlation that is not causal.

Expected Side Effects

Common (usually mild, resolve in days):

  • Fever (up to 1 in 6 children)
  • Mild rash
  • Swelling of glands in cheeks or neck
  • Soreness and redness at injection site
  • Joint pain/stiffness (more common in adult women)

Rare but serious:

  • Febrile seizures (about 1 in 3,000)
  • Temporary low platelet count (about 1 in 25,000)
  • Allergic reaction (very rare)

MMR is given in two doses in early childhood. See exactly when each is due on the CDC vaccine schedule, review our 2026 vaccine schedule analysis, and explore pediatric VAERS patterns.

⚠️ Remember: VAERS reports show correlation, not causation. A report filed after vaccination doesn't mean the vaccine caused the reported event. Always consult your healthcare provider for medical advice.

Explore This Data

MMR Vaccine Detail Page →
Full VAERS profile with charts
Pediatric Analysis →
Childhood vaccine patterns
COVID Vaccine Side Effects →
Compare to COVID data

2026 Safety Monitoring Update

As of mid-2026, the MMR vaccine continues to be monitored through VAERS and complementary surveillance systems including the Vaccine Safety Datalink (VSD) and the Clinical Immunization Safety Assessment (CISA) project. No new safety signals have been identified in recent data that would change the established safety profile of this vaccine.

The HHS administration's announced development of AI-powered VAERS analysis tools may provide additional insights into MMR vaccine adverse event patterns. These tools aim to detect subtle signals that traditional statistical methods might miss, though their implementation timeline and methodology remain under development.

It's worth noting that VAERS reporting for routine vaccines like MMR has remained stable through the post-pandemic period. While COVID-19 vaccine reports surged and then declined, reporting patterns for established childhood and adult vaccines have been remarkably consistent, suggesting that the VAERS system continues to function as designed for ongoing safety surveillance.

Understanding VAERS Data for MMR

When interpreting VAERS data for MMR vaccines, several key principles apply:

  • Reports ≠ Causation: A VAERS report means an event occurred after vaccination. It does not establish that the vaccine caused the event. Many reported symptoms are common health occurrences that would happen regardless of vaccination.
  • No denominator: VAERS does not track the number of doses administered. Without knowing how many people received the vaccine, raw report counts cannot be used to calculate risk rates or compare safety across vaccines.
  • Co-administration: Many vaccines are given at the same visit. When a VAERS report lists multiple vaccines, it's impossible to determine which vaccine (if any) was responsible for the reported adverse event.
  • Reporting variability: Healthcare provider awareness, media attention, and public concern all influence how many reports are filed. Changes in report volume may reflect changes in reporting behavior rather than changes in actual safety.

How to Use This Data Responsibly

VAERS data is most useful as a starting point for conversation with your healthcare provider, not as a basis for medical decisions. If you're concerned about MMR vaccine side effects:

  • Discuss your specific risk factors with your doctor or pharmacist
  • Ask about the relative risks of the disease the vaccine prevents vs. the vaccine itself
  • Consider your age, health status, and any previous vaccine reactions
  • Remember that clinical trials and post-market studies provide much stronger safety evidence than VAERS alone

For the most up-to-date safety information, consult the CDC's vaccine information pages or speak with a qualified healthcare professional.

More Resources

When Do Side Effects Start?
73% occur within 3 days of vaccination
Serious vs Non-Serious Outcomes
The full severity spectrum in VAERS
Report an Adverse Event
How to file a VAERS report
Our Methodology
How we process VAERS data

2026 Safety Monitoring Update

As of mid-2026, the MMR vaccine continues to be monitored through VAERS and complementary surveillance systems including the Vaccine Safety Datalink (VSD) and the Clinical Immunization Safety Assessment (CISA) project. No new safety signals have been identified in recent data that would change the established safety profile of this vaccine.

The HHS administration's announced development of AI-powered VAERS analysis tools may provide additional insights into MMR vaccine adverse event patterns. These tools aim to detect subtle signals that traditional statistical methods might miss, though their implementation timeline and methodology remain under development.

It's worth noting that VAERS reporting for routine vaccines like MMR has remained stable through the post-pandemic period. While COVID-19 vaccine reports surged and then declined, reporting patterns for established childhood and adult vaccines have been remarkably consistent, suggesting that the VAERS system continues to function as designed for ongoing safety surveillance.

Understanding VAERS Data for MMR

When interpreting VAERS data for MMR vaccines, several key principles apply:

  • Reports ≠ Causation: A VAERS report means an event occurred after vaccination. It does not establish that the vaccine caused the event. Many reported symptoms are common health occurrences that would happen regardless of vaccination.
  • No denominator: VAERS does not track the number of doses administered. Without knowing how many people received the vaccine, raw report counts cannot be used to calculate risk rates or compare safety across vaccines.
  • Co-administration: Many vaccines are given at the same visit. When a VAERS report lists multiple vaccines, it's impossible to determine which vaccine (if any) was responsible for the reported adverse event.
  • Reporting variability: Healthcare provider awareness, media attention, and public concern all influence how many reports are filed. Changes in report volume may reflect changes in reporting behavior rather than changes in actual safety.

How to Use This Data Responsibly

VAERS data is most useful as a starting point for conversation with your healthcare provider, not as a basis for medical decisions. If you're concerned about MMR vaccine side effects:

  • Discuss your specific risk factors with your doctor or pharmacist
  • Ask about the relative risks of the disease the vaccine prevents vs. the vaccine itself
  • Consider your age, health status, and any previous vaccine reactions
  • Remember that clinical trials and post-market studies provide much stronger safety evidence than VAERS alone

For the most up-to-date safety information, consult the CDC's vaccine information pages or speak with a qualified healthcare professional.

More Resources

When Do Side Effects Start?
73% occur within 3 days of vaccination
Serious vs Non-Serious Outcomes
The full severity spectrum in VAERS
Report an Adverse Event
How to file a VAERS report
Our Methodology
How we process VAERS data

More Side Effect Guides

All Vaccine Side Effects
Overview across all vaccines
COVID-19 Side Effects
1.1M+ reports analyzed
Full Dashboard
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