Vaccines against infectious diseases are one of the great success stories of modern medicine. Their widespread use has practically eliminated some terrible diseases, like smallpox and polio, and has greatly reduced the incidence of some former scourges of childhood, such as measles and pertussis (whooping cough). Vaccination programs work in two ways. The first, and most obvious way, is the stimulation of immunity to the disease pathogen in the vaccinated individual. The second is the production, when vaccination rates are high, of what is called “herd immunity”. By reducing the number of individuals susceptible to infection, this makes it harder for the disease to spread; it also provides protection to those who are unable to be vaccinated, perhaps because of allergies or compromised immune systems. This is the reason that smallpox vaccination, for example, has historically been required for all children entering school.
Some recent research, reported in an article at Science Daily, highlights some recent trends that might reduce the effectiveness of vaccination in promoting public health. Some US states allow parents to obtain “personal belief” exemptions from vaccinations that would otherwise be compulsory. A group of researchers from the University of Pennsylvania School of Nursing studied vaccination data from more than 7,000 public and private schools in California, which allows personal belief exemptions; the data cover ~500,000 kindergarten students. Just looking at the period from 2008 to 2010, the number of students with one or more exemptions increased by 25%. Also, some schools and school districts had very high rates of exemption; in one county in northern California, nearly half the students were not vaccinated due to exemptions.
The public health implications of losing vaccination’s benefits should not be underestimated.
Measles once infected four million people and killed 4,000 of them each year, mostly young children. With high measles vaccine coverage over several decades, endemic measles was eliminated in the United States as of 2000. The current routine childhood immunization schedule is estimated to prevent 42,000 deaths and 20 million cases of disease and to save $14 billion in direct medical costs per U.S. birth cohort.
There will always be a few individuals for whom vaccination is not a good idea, for sound medical reasons. But skipping vaccinations on the basis of junk science and fashion puts everyone at greater risk.