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What Are the Dangers of Exposing an Infant to Unvaccinated Children?

by Sharon Perkins , studioD

Unvaccinated children pose a risk to themselves and others. The populations most at risk for contracting an infectious disease from an unvaccinated child include infants because their immune systems aren't fully functional. Infants often receive passive immunity to infectious diseases from their moms, but it generally doesn't last beyond a few months. Once your baby receives his immunizations, his risk of contracting a disease from an unvaccinated child decreases, although no vaccine works 100 percent of the time, according to a story at Scholastic.com.

Catching an Infectious Disease

Just being around an unvaccinated child doesn't mean your baby will contract an infectious disease. If the unvaccinated child isn't ill himself, he can't pass on an infectious disease. The problem occurs when you expose an infant whose passive immunity has worn off and who hasn't yet received his immunizations to a child who has been exposed to an infectious disease. The contagious period for many diseases begins a few days before symptoms appear, so your child could contract the disease from a healthy-appearing child who is infectious, according to the Child's Physician Network. In addition, your baby must come in contact with the unvaccinated child or his infected secretions to contract an infectious disease.

Passive Immunity

If you've had infectious diseases such as chicken pox or measles or if you were vaccinated against them, the antibodies in your blood pass through the placenta to your baby. This occurs in the last three months of pregnancy, so premature babies, whose immune systems are also less developed, might not have enough antibodies for full immunity. Passive immunity wears off at different times, depending on the disease. Whooping cough, or pertussis and haemophilus influenza Type B, which causes meningitis, wear off fairly quickly, which is why they're among the first vaccines on the immunization schedule, the British National Health Service explains. Measles, mumps and rubella antibodies remain longer, so doctors normally give those vaccines around age 1 year.

Herd Immunity

Parents of unvaccinated children depend on herd immunity to keep the unvaccinated children from contracting a disease. Herd immunity means that if a large enough percentage of parents vaccinate their children, the risk of exposure and the opportunity for a disease to spread shrinks. Over time, a disease will disappear completely. This has happened with smallpox. For that reason, doctors no longer give smallpox vaccines. If the percentage of vaccinated people falls below 90 percent to 95 percent, the disease will likely become active again, pediatrician Dr. Dan Brennan explains on WebMD.

Protecting Your Baby

If you live in a community where most parents vaccinate their children, herd immunity will protect those who don't, most of the time, notes pediatrician and author Dr. William Sears. Because of that, it's not necessary to keep your baby away from unvaccinated children. If you know an unvaccinated child has been exposed to an infectious disease and your baby hasn't received his immunizations yet, it's safer to keep him away. Don't count on passive immunity to keep your baby safe, because the degree of immunity might differ from child to child.

About the Author

A registered nurse with more than 25 years of experience in oncology, labor/delivery, neonatal intensive care, infertility and ophthalmology, Sharon Perkins has also coauthored and edited numerous health books for the Wiley "Dummies" series. Perkins also has extensive experience working in home health with medically fragile pediatric patients.

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