TRUCKEE, Calif. - On Sept. 30, Governor Jerry Brown signed Assembly Bill 2109. In 2014, parents who do not wish to immunize their children are required to have their health care provider sign a form that states they have been informed about the benefits and risks of immunization before their child is allowed to attend a school or daycare while not fully immunized. The purpose is to ensure that parents fully understand the implications of vaccine declination and to prevent disease outbreaks by maximizing immunization rates.
While the preventable infections that, 100 years ago, accounted for 40 percent of deaths in America seem like a distant memory, they continue to contribute to substantial pain and suffering in other parts of the world where vaccination is less widely available. According to the World Health Organization, 1.5 million children under 5 years of age died in 2008 as a result of vaccine-preventable diseases.
Among the worst offenders is Rotavirus, which causes severe diarrhea, potentially leading to dehydration and death. Rotavirus caused up to 70 thousand hospitalizations per year in America, which has been reduced by 85 percent since the vaccination began. In contrast, serious reactions to vaccines are rare, ranging from 1 in 100,000 to 1 in a million.
In a susceptible population, diseases spread like fire. Much like making materials fire-retardant, immunization increases resistance to the disease in question, making its spread difficult, but a minimum percentage of people must be vaccinated for this to occur. This is called "herd immunity."
Herd immunity usually requires 85-95 percent of susceptible persons to be vaccinated, depending upon the disease. For example, whooping cough (pertussis) requires closer to 95 percent and must be boosted relatively frequently, especially in adults who will be around newborn babies, while mumps requires closer to 85 percent. Nationally, kindergarten vaccination rates are about 95 percent, but this is not evenly distributed. For example, in California counties Nevada and Trinity, rates fall below 85 percent, increasing our vulnerability to future outbreaks of serious diseases.
There is a small subset of persons who cannot safely receive all vaccines, such as newborn babies, organ transplant recipients, and AIDS patients. Herd immunity must be reached to protect them indirectly, by preventing disease from spreading to them in the first place. Declining immunization increases the risk both to those who decline the vaccine as well as to others who cannot receive it even if they would like to.
It should also be emphasized that vaccines are not normally 100 percent effective. While most unimmunized persons will get sick with enough exposure, a minority of vaccinated individuals will as well. This makes herd immunity all the more important, because even the immunized are at higher risk when herd immunity is lacking due to high rates of declination.
With international travel to and from beautiful places like Tahoe, some exposure to these diseases is likely over time. Assembly Bill 2109 presents a great opportunity to talk to your health care provider about immunizations.
Trevor Starnes is a third-year medical student from UC Davis finishing a rural primary care rotation in Truckee.