On kidsdata.org, immunizations are measured by the number and percentage of kindergartners who receive all required immunizations by the time they enter school, along with the number and percentage of kindergartners who are exempt from immunization requirements, by type of exemption.

Also provided are numbers and rates of reported cases of vaccine-preventable childhood diseases—diphtheria, hepatitis A, hepatitis B (acute), measles, meningococcal disease, mumps, pertussis, polio, rubella, tetanus, and varicella—in the total population.

Immunizations are among the most successful and cost-effective preventive health care interventions, protecting millions of children worldwide from serious and potentially fatal infectious diseases (1, 2). For U.S. children born between 1994 and 2021 who receive recommended vaccinations, it is estimated that more than a million lives will be saved and 472 million illnesses prevented, at a savings of nearly $2.2 trillion in direct and indirect social costs (2). Current immunization schedules recommend that children receive vaccinations for diseases such as measles, mumps, whooping cough (pertussis), polio, chickenpox (varicella), and hepatitis (3). Annual immunization against influenza also is recommended. Vaccinations are important for the protection of the individual child as well as for the protection of others with whom an infected child might come into contact, as most vaccine-preventable diseases are spread through air or direct contact (3).

Vaccine hesitancy—identified by the World Health Organization among its top public health threats—has been linked to an increase in vaccine-preventable disease outbreaks in the U.S. (1). Equitable access to vaccines is another major issue, with U.S. data showing persistent disparities in children's vaccination coverage by region, income level, health insurance status, and race/ethnicity (4).

In 2020, 94.3% of California kindergartners had received all state-required immunizations by the time they entered school, up from a low of 90.2% in 2014. Across counties with data in 2020, the share of kindergarteners with all required immunizations ranged from more than 97% to less than 80%. In some school districts, fewer than half of children entering kindergarten had completed all immunization series.

Statewide, 31,669 kindergartners (5.7%) were exempt from immunization requirements in 2020. Among these children, 5,268 (1%) had permanent medical exemptions, 8,227 (1.5%) were overdue for one or more required doses, and 9,188 (1.7%) were conditional entrants, i.e., children who have temporary medical exemptions or are missing (but not overdue for) required doses. Personal belief exemptions peaked in 2014 at 3.2%, but are no longer permitted as of 2017. The share of California kindergartners overdue for one or more required immunizations jumped from 0.2% to 1% between 2016 and 2017, and from 1.1% in 2019 to 1.5% in 2020—the first year a second dose of varicella vaccine was required.

In 2020, 1,073 cases of vaccine-preventable childhood diseases—hepatitis A, hepatitis B (acute), measles, meningococcal disease, mumps, pertussis, tetanus, and varicella (hospitalizations and deaths only)—were reported to the state department of public health. Pertussis (whooping cough) accounts for a majority of infections reported each year—698 (65%) in 2020, a rate of 1.8 cases per 100,000 Californians of all ages. These figures are down from 2019, when there were 4,849 cases—12.2 per 100,000 Californians. Statewide rates of pertussis in the total population peaked in 2014 (29 cases per 100,000) and 2010 (24.5 cases per 100,000). Pertussis outbreaks are cyclic, with peaks every three to five years.

Infectious diseases continue to be a major cause of illness and death in the U.S., despite overall improvements in immunization rates in recent decades (1, 2). Because California law requires proof of vaccinations as a condition of entry into licensed child care, preschool, and public or private elementary and secondary schools, immunization rates are relatively high for children in those settings (3, 4). Outside of those settings, it is critical to ensure that young children receive routine vaccinations and that adolescents complete all recommended vaccination series (1, 5). While progress has been made, immunization coverage continues to vary by geographic, socioeconomic, and other demographic factors, indicating ongoing issues of access, education, and confidence in vaccines (4, 5, 6, 7). Policymakers can address these issues by helping to ensure that all children have a regular source of high-quality health care, making vaccinations affordable and accessible, promoting science-based vaccine information, and supporting complementary evidence-based strategies to increase immunization rates (5, 8, 9).

Policy, system, and practice options to improve immunization rates include:

• Ensuring that all young people have affordable, continuous health insurance coverage and access to a medical home (5, 10)
• Reducing out-of-pocket costs for vaccinations, expanding clinic accessibility, and offering vaccinations in alternative settings such as WIC sites or child care facilities (9)
• Maintaining and strengthening programs—such as Vaccines for Children—and other efforts to increase vaccination among low-income and uninsured children, and for women during pregnancy (5, 8, 11)
• Supporting efforts to identify and advance effective strategies to improve immunization rates among adolescents, such as text message reminder systems and vaccine administration at school-based locations (7, 10)
• Equipping health care providers with the tools and training to improve immunization compliance while addressing vaccine hesitancy; strategies include establishing patient trust, presenting vaccinations as the social norm, and personalizing dialogue to address patients’ individual concerns (6, 10)
• Supporting broad public education efforts to counter misinformation and restore confidence in vaccines, ensuring that communication materials and approaches are based in science yet approachable, tailored to specific groups, and linguistically and culturally appropriate (1, 6, 8)
• Expanding and improving electronic immunization information systems in order to improve communication across providers, address unmet needs, and plan future efforts (8, 11)
• Allocating adequate funding for public health services at the federal, state, and local levels so that agencies can effectively respond to vaccine-preventable disease outbreaks, conduct public education, maintain immunization infrastructure, and carry out other critical services (8, 11)