Wednesday, November 21, 2018

Sonoma Medicine

The magazine of the Sonoma County Medical Association

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Sonoma County’s Lagging Immunization Rates

Mark Netherda, MD

In 1990, during the third year of my family practice residency in Fresno, more than 27,000 cases of measles were reported in the United States, with 12,000 cases in California alone–about 10 times the number of cases reported in 1985. Most of the children involved in the outbreak were Southeast Asian refugees, newly arrived and not yet immunized.


In my Valley Children’s Hospital rotation that year, I cared for many children with measles. I remember thinking this outbreak should not be happening in California, not in 1990. After all, measles was a disease of my parents’ and grandparents’ generations. With our great vaccines, how could this be happening? These kids did not just have runny noses, rashes, fevers and conjunctivitis. They were horribly sick: many had encephalitis and pneumonia. By the end of the outbreak in 1991, ten children from Fresno were dead.

The Fresno tragedy serves as an example of what vaccine-preventable diseases can do in a population that is inadequately immunized. Other examples are easy to find. Recent outbreaks of mumps among young adults in the Midwest, as well as a surge in pertussis cases nationwide, have been linked to a lack of adequate immunization coverage. In San Diego in 2008, there were 12 cases of measles among children, all linked to a single index case of an unvaccinated 7-year-old boy who acquired measles on a trip to Switzerland. He infected 11 other children, including his siblings. One infant was hospitalized, and more than 70 people were quarantined, most for 21 days. Further investigation revealed that of the nine infected children who were old enough to have been vaccinated, eight were unvaccinated due to “personal beliefs exemptions.”

Depending on the state, personal beliefs exemptions (PBEs) allow parents or guardians of children to write letters or sign affidavits stating that immunizations are contrary to their beliefs, thereby allowing schools and child care programs to admit children without proof of immunizations. While all states require immunizations for children to enroll in school, 21 states allow PBEs. In addition, all states offer personal medical exemptions (PMEs) for specific, confirmed medical conditions, and 48 states offer religious exemptions.

California has one of the most lax school immunization policies in the country. A parent or guardian need only sign the Personal Beliefs Affidavit on the back of the California School Immunization Record for a child to be granted admission to school without immunizations. According to the California Department of Public Health’s 2007 Kindergarten Assessment Report, 1.56% of students entering kindergarten in California had PBEs.[1] In Sonoma County, the rate was significantly higher: 4.11%, as shown in Table 1.

Sonoma County kindergarteners have a lower rate of all immunizations when compared to the state average; the number of children who are completely immunized at enrollment is nearly 4% lower than the state average. These figures translate to 677 Sonoma County kindergarteners starting school in 2007 without documentation of complete recommended immunizations, including 243 with PBEs.

For children enrolling in child care centers in Sonoma County, the PBE rate is lower than for kindergarteners, but still higher than the state average (see Table 2).[2] In addition, the overall immunization rate for these Sonoma County children is nearly 5% below the state average.

Immunization rates and the use of PBEs also vary dramatically from school district to school district throughout Sonoma County. Even excluding districts with less than 20 entering students, rates of entering kindergarteners who were fully immunized ranged from as high as 97.92% in one district to as low as 53.73% in another, meaning more than 45% of entering kindergarteners were inadequately vaccinated in that district (see map). It is important to note that these low rates of immunizations are not due to children lacking a single immunization type, but are the result of children missing doses of the recommended immunizations, meaning they lack protection to many if not all of the vaccine-preventable diseases.

PBE rates in different districts ranged from as low as 0.0% to as high as 39.78%—nearly ten times the county average! Public and private schools also had overall differing rates of immunization, with 88.75% of public-school kindergarteners having all immunizations versus 85.5% of private-school kindergarteners. Likewise, PBE rates averaged 3.94% for public schools versus 6.62% for private schools. These data reveal that where children enroll in school directly affects their risks of being exposed to a vaccine-preventable disease from an unvaccinated classmate.

Although there may be some differences in the way districts discuss the entry immunization program with parents and report the data to Public Health, these data strongly suggest clusters of geographic and social trends in perceptions and beliefs regarding vaccines. Parents of unimmunized children who are relying on herd immunity (immunity which occurs when a significant enough proportion of a population is immune to an illness to greatly decrease the risk of disease outbreaks or transmission to a non-immune individual) may be overestimating the levels of protection that are actually present. The CDC lists the herd-immunity threshold rate of measles, for example, at 83-94%, significantly above the rates seen in some Sonoma County school districts.[3] Furthermore, because no vaccine is 100% effective, even fully immunized children, not to mention immunosuppressed children and adults, are put at risk by unimmunized children who become infected with vaccine-preventable diseases.

Why is the immunization rate so low in Sonoma County? An analysis by Sonoma County Public Health staff suggests several possible causes, including problems with data collection, obtaining vaccines, public perception, and provider issues.

School nurses or staff who are busy and overburdened collect most of the immunization information for the state. Staffing decreases have made immunization documentation more difficult. Some schools and parents may misuse PBEs as an “easy out” to avoid the hassle of vaccination appointments or locating documentation. A prospective study showed that “training, knowledge, attitudes, and beliefs” of school personnel were associated with the rate of children having exemptions, suggesting that proper training of school personnel involved in school immunization programs is important.[4]

Some children may face barriers in obtaining vaccines in the form of long delays in scheduling clinic appointments. Private insurers may not cover the cost of vaccinations, making them unaffordable for some patients. Also, vaccine shortages and recalls may occasionally cause further delays.

In 1998, a Lancet article suggested a link between MMR vaccine and autism spectrum disorders in children.[5] This theory, now widely disproved and debunked as faulty science, has garnered extensive media coverage and is still held by some groups as a reason against vaccination. Similarly, many parents, naturopathic health groups, and politicians (including Robert Kennedy Jr., who published an article on the subject in Rolling Stone) have voiced concerns about thimerosal, a vaccine preservative containing mercury. Although multiple studies have shown that thimerosal is benign, vaccine manufacturers removed it from all recommended early childhood vaccines in 2001.[6,7]

A case-control study revealed that the most common reason (69%) for parents to request a PBE was the perception that vaccines cause harm.[8] Parents seeking exemptions were more likely to report a low level of confidence in governmental and medical sources of vaccine information and also more likely to report confidence in alternative medicine professionals. These concerns may be a significant contributor to the high proportion of PBEs in Sonoma County.

Physicians play a critical role in the immunization process. Many parents rely on doctors and other health care providers as their primary source of information about immunizations. Such discussions should include details about vaccine-preventable diseases and their potential for morbidity. After all, most young parents, let alone physicians, have never seen these diseases, and they may not understand that measles, for example, is more than just a rash. Parents should be provided with educational information about immunizations and the diseases they protect against, including details on the perceived risks described above. Although one-to-one education is best, handouts (in addition to the required immunization-specific handouts given at the time of vaccination) could be used as well. The American Academy of Family Physicians ( and the American Academy of Pediatrics ( have excellent websites for immunization information.

Another influence on the provision of immunizations is the cost to the provider, as detailed by two articles in the December 2008 issue of Pediatrics.[9,10] The first article presents results from a 2007 survey of pediatricians and family physicians about the types of vaccines they provide; the financial effect that vaccine provision has on their practices; and “the extent to which the practice has considered no longer providing vaccines to insured patients.” A remarkable 11% of the responding practices said they had seriously considered discontinuing the provision of vaccines to insured patients. This sentiment was much higher among responding family physicians (21%) than pediatricians (5%). The authors suggest that in some rural areas, where family physicians are the “dominant source of children’s primary care,” discontinuing the provision of vaccines by family physicians could have a serious impact on the community.

The second Pediatrics article reports on the tremendous variations in cost of vaccines to different private practitioners, and in payments that insurance plans will reimburse to providers for giving vaccines. The price paid for the same vaccine varies by more than 100% from practice to practice, and the reimbursement rate difference is also more than 100% in some cases.

Physicians and medical groups should be aware of the complexity of immunization reimbursement and exactly what financial effect an immunization program has on their practices. Only with this understanding can physicians work to minimize costs by negotiating vaccine prices with manufacturers and reimbursement rates with insurance companies. Physicians should also encourage their professional organizations to continue lobbying for higher reimbursement rates and lower costs of vaccines overall.

The immunization schedule is another burden physicians face in keeping children up to date on vaccinations. The schedule is complicated and can be overwhelming. Anecdotal reports of “immunization fatigue” are common, leading physicians to use alternate or prolonged schedules, which can result in missed doses.

An important tool for relieving some of the immunization burden is CAIR, the California Immunization Registry (see sidebar). This free Internet-based service not only simplifies vaccine record keeping in medical offices, but also helps record and track immunization records of individual children, even as they change physicians or move from city to city. The data collected allows for real-time information regarding immunization coverage. And, because these records are accessible by school systems, widespread use of CAIR will provide a better record of immunization coverage of children in Sonoma County. All physicians offering immunizations to children are urged to use CAIR in their practices.

No matter the reason, too many Sonoma County children are inadequately immunized. Although immunization rates are unlikely ever to reach 100%, the U.S. Department of Health and Human Services does provide realistic goals for vaccination coverage in Healthy People 2010, a “statement of national health objectives designed to identify the most significant preventable threats to health and to establish national goals to reduce these threats.”[11]

For the 2007 kindergarten assessment group, Sonoma County lags behind California state averages but does meet the Healthy People 2010 benchmarks of at least 95% coverage for DTaP, MMR, and polio immunizations. For child care centers, however, the results are far worse. This younger group meets none of the benchmarks. Indeed, state records suggest a decline in immunization rates for Sonoma County from 2001 to 2006.[1] The system is failing these children.

The Fresno and San Diego measles outbreaks reviewed above demonstrate how small groups of unvaccinated children can result in significant disease burdens and morbidity, as well as tremendous costs to the health care system. The San Diego incident provides an additional lesson. Shortly after returning from Switzerland, the index case went to school with a fever and sore throat, and then visited his doctor three days later, at the onset of a rash. Scarlet fever was ruled out by a rapid strep test, and the boy was sent home. He later visited a hospital inpatient laboratory to have a measles antibody titer drawn, and then returned to the emergency department when his condition worsened.

Despite the provisional diagnosis of measles, the boy was never isolated in any health care facility, and his parents were never told to quarantine him. As a result, many people were exposed to measles, creating a disease investigation nightmare for the San Diego Health Department. The lesson here is that physicians need to familiarize themselves with these “old” illnesses and practice good infection control measures whenever a communicable disease is suspected.

Sonoma County is a prime target for similar outbreaks. Public Health is increasing outreach to parents, health care providers, child care centers, and schools to raise immunization levels and is working at the state level to effect policy changes to best protect the children of Sonoma County against vaccine-preventable diseases. Simultaneously, physicians need to be aware of the possibility of local outbreaks and should actively work to promote immunizations for all local children. 




  1. Cal. Dept. of Public Health, 2007 Kindergarten Assessment Report, (2008).
  2. Cal. Dept. of Public Health, 2007 Child Care Assessment Report, (2008).
  3. CDC website, (2008).
  4. Salmon DA, et al, “Knowledge, attitudes and beliefs of school nurses and personnel and associations with nonmedical immunization exemptions,” Pediatrics, 113:552-559 (2004).
  5. Wakefield AJ, et al, “Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children,” Lancet, 351;9103:637-641 (1998).
  6. Safety Review Committee Board on Health Promotion and Disease Prevention, Immunization Safety Review: Vaccines and Autism Immunization, National Academies Press (2004).
  7. Offit P, Autism’s False Prophets, Columbia Univ Press (2008).
  8. Salmon DA, et al, “Factors associated with refusal of childhood vaccines among parents of school-aged children,” Arch Ped Adol Med, 159:470-476 (2005).
  9. Freed GL, et al, “Primary care physician perspectives on reimbursement for childhood immunizations,” Pediatrics, 122;6:1319-24 (2008).
  10. Freed GL, et al, “Variation in provider vaccine purchase prices and payer reimbursement,” Pediatrics, 122;6:1325-31 (2008).
  11. U.S. Dept. of Health and Human Services, Healthy People 2010, 2nd ed., U.S. Govt. Printing Office (2000).

Dr. Netherda is Deputy Public Health Officer for Sonoma County.



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