Measles Outbreak: What Vaccine Leaves a Mark on Your Arm? (2026)

A recent surge in measles cases in Mexico has prompted many to question which vaccine leaves a mark on the left arm. Contrary to popular belief, the mark is not from the measles vaccine itself.

What Vaccine Leaves a Scar?

The round scar seen on the arms of millions is actually from the BCG vaccine, which protects against severe forms of tuberculosis, including tuberculous meningitis. In Mexico, the BCG vaccine is administered to newborns, according to the country’s national vaccination schedule. Tuberculosis is a deadly infectious disease responsible for over a million deaths annually worldwide.

The BCG vaccine is administered on the upper arm, creating a small lesion that eventually forms a permanent scar. This mark indicates the body has developed an immune response.

Experts note that the absence of a scar doesn’t always mean a person isn’t protected, but it can be a signal to check their vaccination record.

Did You Know? The BCG vaccine protects against severe forms of tuberculosis, a disease that remains one of the leading causes of infectious death globally.

How Do I Know If I’ve Had the Measles Vaccine?

The measles vaccine is part of the triple viral (SRP) vaccine, which also protects against rubella and mumps. It is typically administered at one year of age, with a booster dose at six years old.

If you are unsure of your vaccination status, check your national health card, ask your parents, or visit a medical center for confirmation. The measles vaccine is also available for adults who did not complete their vaccination schedule.

Who Should Get Vaccinated Against Measles in 2026?

In 2026, the Secretary of Health recommended verifying complete vaccination schedules, particularly for:

Girls and boys at 18 months, for the second dose of SRP
Children under 6 to 11 months living in areas with active outbreaks
People under 49 years of age who do not have a complete vaccination schedule or do not remember being vaccinated

Those who meet these criteria should visit vaccination modules in Mexico City. A list of nearby locations can be found here.

Expert Insight: The current measles outbreak underscores the importance of maintaining high vaccination rates to protect vulnerable populations and prevent the resurgence of preventable diseases. Ensuring complete vaccination schedules, particularly for those at higher risk, is a critical public health measure.

Frequently Asked Questions

What vaccine leaves a scar on the arm?

The BCG vaccine, which protects against tuberculosis, leaves a scar on the upper arm.

What does the triple viral vaccine protect against?

The triple viral (SRP) vaccine protects against measles, rubella, and mumps.

Who is currently recommended to get the measles vaccine in Mexico?

The Secretary of Health recommends verifying vaccination schedules for children 18 months old for their second dose, children under 6-11 months in outbreak zones, and people under 49 who are not fully vaccinated.

As vaccination efforts continue, will increased public awareness about the difference between the BCG and measles vaccines help to alleviate concerns and encourage more people to verify their immunization status?