Definition: Herd immunity is a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity.
It arises when a high percentage of the population is protected through vaccination against a virus or bacteria, making it difficult for a disease to spread because there are so few susceptible people left to infect. This can effectively stop the spread of disease in the community.
It is particularly crucial for protecting people who cannot be vaccinated. These include children who are too young to be vaccinated, people with immune system problems, and those who are too ill to receive vaccines (such as some cancer patients).
- So when you vaccinate your children and grandchildren, you are also protecting vulnerable members of your community by reducing the spread of disease.
- When you get a flu shot, you are protecting the elderly and immunocompromised from dying of the flu–and some do every year.
- “When the number of people vaccinated drops below 95 percent, a community loses herd immunity to highly contagious germs…”
Looking at the History: the 1950s
In a recent article in TIME Jeffrey Kluger provides great information: in 1952 there were 57,879 cases of paralytic polio in the U. S. By 1961, six years after the Salk vaccine was introduced, that number fell to 1,312, a 98% reduction. Today the figure is zero. Measles?? In the 1950s, 3-5 million of us contracted the disease EACH YEAR! 48,000 of those cases were hospitalized. In 2012 there were only 55 cases. BUT WE DON’T WANT TO GO BACK.
PAST COVERAGE: Some states have excellent rates of coverage: Louisiana 96.6% rate for the MMR and 98.3% for diphtheria, tetanus and pertussis Tdap. Mississippi boasts a near perfect 99.9% but California, with its contributing figures from Orange County where mothers often listen to a certain pediatrician who tells them not to vaccinate if they don’t want to, has only 92.7% for the MMR and 92.5% for Tdap. This is serious. Populations cannot afford the numbers to drop below 95%. It puts many people at risk. It puts immunocompromised people, infants and cancer patients at risk.
Fighting Back
Jeffrey Kluger reports that some medical professionals are able to convince parents to vaccinate by using these measures:
- Relating the consequences of getting the disease:
mumps: deafness, inflammation of the brain (encephalitis), inflammation of testes which can cause a drop in the sperm count, and inflammation of the ovaries, though fertility is not affected;
measles: ear infections, pneumonia, encephalitis; and in a pregnancy miscarriage or premature birth; death: one or two out of 1,000 die;
German measles, rubella: poses a grave danger to a pregnant woman’s fetus and can cause miscarriage or birth defects, like deafness, intellectual disability, heart defects; 85 out of 100 babies born to mothers who had rubella in the first 3 months of her pregnancy will have a birth defect.
- MOBI– maximizing office-based immunizations–in other words, taking the opportunity to offer vaccines to children whenever they appear in the medical office. “We think people listen to their providers, says Mary DiOrio, the state of Ohio’s epidemiologist.
- Laws.49 of the 50 states have laws that require kids to be vaccinated before attending public schools and daycare centers. (at least they did…not sure now) PROBLEM: parents can utilize an opt-out form for religious reasons–but this can be exploited.
- Some schools are now permitted to require unvaccinated children to stay home during outbreaks, and to bar them from school activities. T
- The Autism Component
The initial fears that the MMR contributed to the rise of autism might still be circulating, though the research has found that to be totally inaccurate. As Kluger writes: “The vaccine opponents are not going away anytime soon (RFK)….”
For more information talk to your pediatrician.
On Immunity: An Inoculation by Eula Bliss Graywolf
Who’s Afraid of a Little Vaccine? by Jeffrey Kluger
