Folks who are intentionally unvaccinated often have a hard time understanding why the rest of us might be a little leery of being around them.
That’s especially true if we have a new baby in the house, younger kids who aren’t fully vaccinated and protected, or anyone with a chronic medical condition who can’t be vaccinated.
Why? Of course, it is because we don’t want them to catch measles, pertussis, or other vaccine-preventable diseases.
“How can you spread a disease that you don’t even have?”
It’s true, you can’t spread a disease that you don’t have.
But infectious diseases don’t magically appear inside our bodies – we catch them from other people. And if you have skipped or delayed a vaccine, then you have a much higher chance of getting a vaccine-preventable disease than someone who is vaccinated and protected.
So, just avoid other people when you are sick, right?
“…the increased risk of disease in the pediatric population, in part because of increasing rates of vaccine refusal and in some circumstances more rapid loss of immunity, increases potential exposure of immunodeficient children.”
Medical Advisory Committee of the Immune Deficiency Foundation
That works great in theory, but since you are often contagious before you show signs and symptoms and know that you are sick, you can very easily spread a disease that you don’t even know that you have.

There’s the trouble:
- being unvaccinated, you or your child are at higher risk to get sick
- when you get sick, you can be contagious several days before you have obvious symptoms
- you can spread the disease to others before you ever know that you are sick, or at least before you know that you have a vaccine preventable disease
This makes intentionally unvaccinated folks a risk to those who are too young to be vaccinated, are too young to be fully vaccinated, have a true medical exemption to getting vaccinated, or when their vaccine simply didn’t work.

In fact, this is how most outbreaks start. Tragically, kids too young to be vaccinated get caught up in these outbreaks.
Keep in mind that these parents didn’t have a choice about getting them protected yet. Someone who decided to skip their own vaccines made that choice for them.
And remember that while you can’t spread a disease that you don’t even have, you can certainly spread a disease that you don’t realize that you have.
What to Know About The Unvaccinated Spreading Disease
If you aren’t going to get vaccinated or vaccinate your kids, understand the risks and responsibilities, so that you don’t spread a vaccine-preventable diseases to others that you might not even know that you have yet.
More on the Unvaccinated Spreading Disease
- CDC – Introduction to Epidemiology
- WHO – Basic Epidemiology
- WHO – Epidemiology of the Unimmunized Child
- To the Parent of the Unvaccinated Child Who Exposed my Family to Measles
- If You Choose Not to Vaccinate Your Child, Understand the Risks and Responsibilities
- Should I Take My Three-Week Old to the Family Reunion?
- Asking Before They Play: Are Your Child’s Friends Vaccinated?
- Ask Before They Play To Keep Chickenpox, Pertussis and Measles Away
- When It’s Not a Choice: Measles and Leukemia
- The Hidden Cost of Avoiding Vaccines
- Growing Up Unvaccinated
- The Unvaccinated Children We Love
- Why Worry About the Unvaccinated?
- Is my unvaccinated family putting my child at risk?
- One more time: Vaccine refusal endangers everyone, not just the unvaccinated
- The Rights of the Unvaccinated Child
- Is Your Child’s Classmate Unvaccinated?
- New Study Emphasizes Harm of Vaccine Refusals
- Ask Well: Playing With Unvaccinated Babies
- Protecting Your Child and Your Community
- Vaccine-preventable Diseases, Immunizations, and the Epidemic Intelligence Service
- Seasonal infectious disease epidemiology
- Why Do So Many Vaccinated People Get the Mumps During an Outbreak?
- The Simple Math of Herd Immunity
- Hey antivaccination gang–it’s really simple math
- Vaccine Awareness Week: If Vaccines Work…
- What Is the Harm in Delaying or Spacing out Vaccines?
- Why Do So Many Vaccinated People Get the Mumps During an Outbreak?
- Study – A Measles Outbreak in an Underimmunized Amish Community in Ohio.
- Study – An outbreak of measles in an undervaccinated community.
- CDC – Notes from the Field: Measles Outbreak Associated with a Traveler Returning from India — North Carolina, April–May 2013
- CDC – Notes from the Field: Outbreak of Pertussis in a School and Religious Community Averse to Health Care and Vaccinations — Columbia County, Florida, 2013
- Study – Sustained Transmission of Pertussis in Vaccinated, 1–5-Year-Old Children in a Preschool, Florida, USA
- Report – Medical Advisory Committee of the Immune Deficiency Foundation. Recommendations for live viral and bacterial vaccines in immunodeficient patients and their close contacts
This doesn’t answer the question as to why unvaccinated children spread disease. If a vaccinated child contracted measles, for instance, he or she would also be contagious 4 days before showing symptoms. So how is an unvaccinated child spreading disease, when the incubation time is the same whether one has been vaccinated or not?
Unvaccinated children don’t spread the disease unless they get it, but they are very likely (around 90%) to get it if they are in contact with someone who has it or the air space/ surfaces they have recently touched. Someone who has been vaccinated has only a 3% chance of getting measles if they are exposed,
so they can spread the disease, too, but the likelihood is much smaller.