Immunizations protect your child and you from vaccine-preventable diseases, which can cause life-threatening infections. Being vaccinated also protects everyone around you.

Herd immunity dictates that if most people are immune to a disease, then it will be unlikely that anyone will get sick and infect anyone in the herd, including those who are unprotected.﻿﻿

Although many who purposely don't vaccinate their children or themselves claim they aren't part of the herd or don't believe in herd immunity, they still are. They are simply an unprotected member of the herd who relies on the rest of us for protection.﻿﻿

So who is put at risk when someone chooses to not get vaccinated?

Myths and Misconceptions

One of the classic myths or misconceptions that anti-vax folks use to justify starting outbreaks of vaccine-preventable diseases is saying that their intentionally unvaccinated kids pose no risk to the rest of us because we have all had our vaccines.

They typically think that it is only their own unvaccinated children and themselves who will be at risk for vaccine-preventable diseases, which they often think are not dangerous, another classic anti-vax myth. Unfortunately, as the increasing number of outbreaks of measles in the United States are showing, neither anti-vax myth is true.

In fact, as we continue to hit new records, we are seeing:

Infants who are too young to be vaccinated get caught up in the outbreaks as they are exposed at a doctor's office or hospital, where the person with measles is seeking care.

People with immune system problems getting needlessly exposed to measles, as happened in Pittsburgh, when a college student with measles possibly exposed about 100 cancer patients.

People develop severe complications of measles, such as the healthcare provider who reportedly developed measles encephalitis during the large measles outbreak in Fort Worth.

We are also learning how much it costs to contain a measles outbreak. In 2011, there were 107 confirmed measles infections in the United States. To contain the outbreaks, local and state health departments had to spend between $2.7 and $5.3 million, according to a study from the Centers for Disease Control and Prevention.

Too Young to Be Vaccinated

Among the groups of people who are most at risk from those who are unvaccinated are infants and children who are simply too young to be vaccinated.

These are often the children of parents who plan on getting them fully vaccinated, following the latest immunization schedule of the American Academy of Pediatrics, but they just aren't old enough yet to be protected.

This is an especially big problem with pertussis (whooping cough) when infants don't begin to have any protection until they get their third dose of the DTaP vaccine when they are six months old. In the California pertussis outbreak of 2010, 10 infants died, nine of whom were less than two months old.﻿﻿ ﻿﻿

And we see this with measles too, since children don't get their first dose of the MMR vaccine until they are twelve months old and aren't fully protected until they get the second dose, at age four years. (Keep in mind that young children should get their MMR doses earlier if they will be traveling out of the United States.)﻿﻿

Younger children can be at risk for vaccine-preventable diseases until they are old enough to get their vaccines:

Influenza vaccination is scheduled so that the first dose is given at age six months with a second dose delivered a month later. ﻿ ﻿

﻿ Chickenpox, like measles, is scheduled so that children get their first vaccine dose at 12 months and the second dose at age four years. The second dose can be given as early as three months after the first dose though, especially if your child was recently exposed to chickenpox. ﻿ ﻿

﻿ Younger children are also at risk for polio, rubella, and mumps until they are old enough to be vaccinated.

Considering that there are about 4,000,000 births a year in the United States, that puts a lot of infants at risk for measles, pertussis, and other vaccine-preventable diseases.

For measles, as kids aren't fully protected until they get their second dose of the MMR vaccine when they are about four-years-old, that means an additional 12,000,000 toddlers and preschoolers are potentially at risk.

Recommended Vaccination Before Age 2 Hepatitis A

Rotavirus

Diphtheria, tetanus, and acellular pertussis (DTaP)

Pneumococcal conjugate

Inactivated poliovirus

Influenza

Measles, mumps, and rubella (MMR)

Varicella

Haemophilus influenzae type B

Weak Immune System

Children and adults with weak immune systems can fall into several broad categories. These include those who can't receive some vaccines because they have a weak immune system.

There are also those who may be fully vaccinated, but no longer have any immune protection because they developed an immune system problem. And if they were to be vaccinated, depending on their degree of immune suppression, the vaccine likely would not work well.

There are at least 180 different types of primary immune deficiency disorders and many secondary ones. Among these immune system disorders that might put children at risk for some vaccine-preventable diseases include:

Antibody deficiencies such as X-linked agammaglobulinemia, common variable immunodeficiency, selective IgA deficiency, IgG subclass deficiency

Partial and complete T-lymphocyte defects such as severe combined immunodeficiency (SCID) disease, DiGeorge syndrome, Wiskott-Aldrich syndrome, ataxia-telangiectasia

Defects in phagocyte function such as chronic granulomatous disease, leukocyte adhesion defect, and myeloperoxidase deficiency

HIV/AIDS

Many kinds of cancer

Transplants receiving immunosuppressive therapy

A disorder requiring treatment with immunosuppressive doses of steroids

According to the Immune Deficiency Foundation, "We want to create a 'protective cocoon' of immunized persons surrounding patients with primary immunodeficiency diseases so that they have less chance of being exposed to a potentially serious infection like influenza."

It shouldn't be hard to see that if some children are intentionally not getting vaccinated, then they certainly do pose a risk for these children with immune system problems.

A CDC report of the death of a vaccinated child with leukemia is a heartbreaking illustration of how kids with immune system problems can be at high risk from vaccine-preventable diseases.

The 4-year-old with acute lymphoblastic leukemia (ALL) developed a fever 22 days after being exposed to chickenpox and just after starting another round of chemotherapy, which causes profound immunosuppression. She was hospitalized and died of multi-organ failure a few days later.

The Immune Deficiency Foundation warns of increasing rates of disease and illness in immune-deficient children due to the legion of parents who refuse to vaccinate their immune-competent kids.

Cannot Be Vaccinated

There are also situations where a child might be old enough to be vaccinated and has a strong immune system but still can't get some or all of his vaccines.

Although not common, the most well known would be a child who had a life-threatening allergic reaction to a previous dose of the vaccine or a component of the vaccine. For example, if you have had a life-threatening reaction to the antibiotic neomycin, then you shouldn't be vaccinated with the chickenpox, polio, or MMR vaccines.

These are the children who have true medical exemptions to getting vaccinated.﻿﻿

Vaccinated and Unprotected

Vaccines are effective. By the time most children are 2 years old, they are protected against 14 vaccine-preventable diseases, including diphtheria, Haemophilus influenzae type b, measles, mumps, pertussis, and polio, etc.﻿﻿

Some vaccines are more effective than others. For example, the measles vaccine is over 97% effective at preventing measles after two doses. By contrast, the acellular pertussis vaccine is only around 80 to 90% percent effective.

Even if the measles vaccine is over 99% effective, if there are almost 74,000,000 children and teens under age 18 years in the United States, that would still put a lot of kids at risk from people who are intentionally not vaccinated.

Whether it is a 6-month-old going to the pediatrician for a "well child" check-up, a 6-year-old with leukemia going to the hospital for chemotherapy, or a 16-year-old with chronic granulomatous disease, it should be clear that a lot of people are unnecessarily put at risk when someone makes a decision to not vaccinate their kids or to use an alternative immunization schedule.