Childhood Immunization Status (CIS, CIS-E)

The percentage of persons 2 years of age who had four immunizations for diphtheria, tetanus  and acellular pertussis (DTaP); three immunizations for poliomyelitis (IPV); one immunization for measles, mumps and rubella (MMR); three immunizations for haemophilus influenza type B (HiB); three immunizations for hepatitis B (HepB); one immunization for chicken pox (VZV); four pneumococcal conjugate (PCV) immunizations; one immunization for hepatitis A (HepA); two or three immunizations for rotavirus (RV); and two immunizations for influenza (flu) by their second birthday. The measure calculates a rate for each vaccine and three combination rates.

Why It Matters?

The percentage of persons 2 years of age who had four immunizations for diphtheria, tetanus  and acellular pertussis (DTaP); three immunizations for poliomyelitis (IPV); one immunization for measles, mumps and rubella (MMR); three immunizations for haemophilus influenza type B (HiB); three immunizations for hepatitis B (HepB); one immunization for chicken pox (VZV); four pneumococcal conjugate (PCV) immunizations; one immunization for hepatitis A (HepA); two or three immunizations for rotavirus (RV); and two immunizations for influenza (flu) by their second birthday. The measure calculates a rate for each vaccine and three combination rates.

Why It Matters

This measure focuses on improving immunization rates for vaccines that children should receive by their second birthday. This measure is based on the best available evidence which recommends vaccination against DTaP, IPV, MMR, HiB, HepB, VZV, PCV, HepA, RV and flu for children by 24 months of age ^[1,2,3].

Among children born in the United States between 1994 and 2023, routine childhood immunizations were estimated to have prevented approximately 508 million childhood illnesses, 32 million hospitalizations and 1.13 million deaths over their lifetime, resulting in a net savings of approximately $540 billion in direct costs and $2.7 trillion in societal costs ^[4]. As a note, this study did not include influenza, COVID-19 or RSV so the overall benefits are likely underestimated.

Diphtheria can present as a respiratory or cutaneous disease ^[5]. Complications include myocarditis, which can lead to heart failure, and neuritis, which may temporarily paralyze motor nerves. Death occurs in 5%–10% of cases, with a higher mortality rate in young children ^{[5, 6]}. Tetanus infection is associated with the painful tightening of skeletal muscles. The resulting muscle spasms can cause fractures, difficulty breathing, arrhythmia and death ^[7]. Without intensive care, almost all cases of tetanus are fatal  ^[8]. Acellular pertussis, also known as whooping cough, is a highly communicable respiratory infection characterized by a prolonged cough ^[9]. While pertussis is usually mild in children, adolescents and adults, infected infants are more likely to experience severe complications, including apnea, pneumonia, pulmonary hypertension and death. Unvaccinated infants under 6 months account for most pertussis-related hospitalizations and mortality ^[10].

While there are three combination vaccines (DTaP, Td and Tdap) that offer protection against diphtheria, tetanus and acellular pertussis, only the DTaP vaccine series is recommended for infants and young children ^[1,2,3]. Before the development of these vaccines, diphtheria was a common cause of death in children and adolescents. The diphtheria vaccine has virtually eliminated the disease in the U.S.^{[5, 11]}. Similarly, widespread use of the pertussis vaccine since the 1940s has decreased U.S. pertussis cases by 75% ^[12]. Routine vaccination schedules for children recommend administering DTaP to all children via a 3-dose series prior to age two. Boosters are recommended at age 15–18 months and 4–6 years ^[1,2,3].

Poliomyelitis, or polio, is a highly communicable virus that affects the nervous system. It mainly affects children younger than five years of age however any unvaccinated individual may contract the disease ^[13]. Approximately one in four individuals infected with polio experience flu-like symptoms such as sore throat, fever, fatigue, headache, vomiting and limb pain. In some cases, infection leads to more serious symptoms, such as meningitis, irreversible paralysis and death. While affected individuals may appear to fully recover, these more severe symptoms can re-emerge within 15-40 years of initial infection ^[14].

While there is no cure for polio, broad immunization uptake eliminated the disease from the U.S. in 1979 and from the Western Hemisphere in 1991 ^[15] (Children’s Hospital of Philadelphia, n.d.-c). Because polio still occurs in other parts of the world, IPV remains a core component of routine childhood immunization schedules in the U.S.^[1,2,3]. IPV is administered in a 4-dose series with the first three doses occurring prior to age two and the fourth between ages 4 and 6. Two doses of the IPV vaccine prevents approximately 90% of severe disease cases, while three doses of the IPV vaccine prevents approximately 99% of severe disease cases ^[14].

Measles, or rubeola, is a highly communicable virus spread by respiratory droplets, small particle aerosols and close contact. While the disease is typically associated with fever, cough, coryza, conjunctivitis and rash, infected infants and children younger than 5 years of age are susceptible to severe complications, including pneumonia infection, neurological complications such as brain damage, blindness, hearing loss and death ^[16]. Mumps is a virus that can cause milder, flu-like symptoms and parotitis, or swollen salivary glands. In rare cases, infection can result in severe complications such as pancreatitis, encephalitis, meningitis, orchitis, oophoritis, mastitis and hearing loss ^[17]. Rubella is a highly communicable virus similar to measles. While it is typically associated with mild symptoms such as rash, lymphadenopathy and fever, infected children can experience complications such as polyarthritis and polyarthralgia ^[18](Camejo Leonor et al. 2026).

Receiving multiple doses of the MMR vaccine is demonstrably effective for preventing measles, mumps and rubella and is included in recommendations for routine childhood immunizations in the U.S. ^[1,2,3]. Routine U.S. childhood immunization schedules recommend two doses of the MMR vaccine with the first occurring before age two. The second dose occurs between ages 4 and 6. Two doses of the MMR vaccine prevents approximately 99% of measles cases; its widespread use effectively eliminated measles in the U.S. in 2000 ^[19]. Similarly, the MMR vaccine is over 95% effective in preventing mumps and 90% effective at preventing rubella after a single dose ^[20].

Haemophilus influenzae type B (HiB) is a serious bacterial infection spread through respiratory droplets and prolonged contact with infected individuals. It is most common in infants and children aged five years and less and in adults 65 years and older ^[21]. It can cause ear infections, pneumonia, meningitis, sepsis, epiglottitis and other severe infections of the skin and joints. In children, these infections can cause coma, paralysis, deafness, blindness, mental impairments and death ^[22].

While HiB can be treated using antibiotics, severe cases may require intensive care ^[47]. Prevention is possible via vaccination and recommended by U.S. childhood immunization schedules. These schedules recommend three doses of the HiB immunization for all individuals by two years of age ^[1,2,3]. Widespread use of the Hib vaccine in the U.S. since the early 1900s has resulted in a dramatic decline in the incidence of meningitis, bloodstream infections and pneumonia caused by HiB ^[22].

Hepatitis B is a highly contagious, viral liver disease transmitted by bodily fluids. It can manifest chronically where most people are asymptomatic or acutely with symptoms of fever, fatigue, loss of appetite, jaundice and body pains ^[23]. Approximately 90% of infected infants and 30% of infected children experience chronic infection, which can lead to progressive, lifelong liver damage, cirrhosis and liver ^[24,25]. In 2023, there were an estimated 14,400 new cases of acute hepatitis B, 17,650 cases of newly-reported chronic hepatitis B and 1,769 hepatitis-B related deaths ^[26].

Routine childhood immunization schedules recommend universal hepatitis B immunization for all infants and unvaccinated children ^[1,2,3]. Prior to the routine use of the hepatitis B vaccine, there were about 9.6 per 100,000 cases of acute hepatitis B viral infection. This number dropped after the introduction of the vaccine. In 2018, there were about 1 per 100,000 cases reported ^[24].

Chicken pox, also known as varicella, is an extremely communicable disease characterized by a full-body skin rash. While symptoms are typically mild, infection can sometimes result in pneumonia, encephalitis, death and shingles (herpes zoster) later in life ^[27]. In the U.S., the varicella zoster virus accounts for more than 9,000 hospitalizations annually, with the highest prevalence among children aged 4- to 10 years ^[28].

In the U.S., widespread vaccination for varicella-zoster since 1995 has reduced the number of new annual varicella cases by approximately 85%^[27]. Before the introduction of this vaccine approximately 90% of children in the U.S. contracted varicella by age 10, resulting in high subsequent rates of herpes zoster infections in adults ^[28]. U.S. routine childhood immunization schedules recommend varicella immunizations to prevent infectious morbidity for both varicella and herpes zoster later in life ^[1,2,3].

Pneumococcal disease (e.g., pneumonia, bacteremia, meningitis) can present as mild to very serious in young children. Children aged less than 5 years are at higher risk for these diseases; in the U.S., this amounts to approximately 1,500 cases of severe infection per year for individuals aged five years and younger ^{[29, 30]}. Pneumonia symptoms generally include fever, chills, pleuritic chest pain, cough with sputum, dyspnea, tachypnea, hypoxia tachycardia, malaise and weakness ^[31,32]. It is the leading cause of mortality among young children worldwide ^[33] (Neuman and Rees 2025). Bacteremia is a blood infection with a 20% mortality rate among all adults and similarly severe outcomes among children ^[34]. Meningitis may cause headache, lethargy, vomiting, irritability, fever, nuchal rigidity, cranial nerve signs, seizures and coma ^[35]. In particularly vulnerable populations (i.e., children less than five years of age), these diseases can cause death or lifelong disability, including deafness, brain damage and medically necessary limb amputation ^[30].

Pneumococcal vaccines have been shown to be highly effective in preventing invasive pneumococcal disease, and routine U.S. childhood immunization schedules recommend that all children younger than five years of age are vaccinated with four doses of the pneumococcal conjugate vaccines ^{[1,2,3, 36]}. When comparing costs, outcomes and QALY, immunization with recommended pneumococcal vaccines was found to be economically efficient ^[37].

Hepatitis A is a highly contagious, viral liver disease transmitted by close physical contact with an infected person or ingesting contaminated food or drink. Symptoms, including discolored urine or stool, diarrhea, fatigue, fever, joint pain, nausea and jaundice, are less common in children than in adults, and typically last for 2-6 months ^[38]. Severe complications are rare but may include liver failure and death.

Routine U.S. childhood immunization schedules recommend universal hepatitis A immunization for all infants and unvaccinated children, administered via one dose by age two ^[1,2,3]. A second dose is administered six to twelve months later. This vaccine provides long-term protection against hepatitis A infection [39.

Rotavirus is a highly contagious disease typically associated with symptoms of fever, vomiting and diarrhea. Most children are infected with rotavirus by age 5, particularly between the months of November and May ^[40]. Although the symptoms are typically mild, they can easily lead to dehydration, particularly in children less than one year old. If unmitigated, severe dehydration due to rotavirus can lead to convulsions or shock ^[40].

Routine U.S. childhood immunization schedules recommend the rotavirus vaccine, with 2-3 doses administered prior to age two ^[1,2,3]. Prior to the introduction of the rotavirus vaccine there were an estimated 2.7 million cases of rotavirus per year with 95%of children infected by 5 years of age ^[41]. Following the introduction of the rotavirus vaccine, 280,000 clinic visits, 62,000 emergency department visits and 45,000 hospitalizations have been averted annually ^[41].

Influenza is a serious disease that is characterized by a variety of symptoms related to the nose, throat and lungs that can range in severity and lead to hospitalization and death ^{[42, 43]}. Infected children younger than two years of age face a higher risk of developing severe symptoms and complications, including sinus infections, ear infections, pneumococcal disease, myocarditis, encephalitis, sepsis, respiratory failure, kidney failure and death ^[43]. This risk increases for children with comorbid asthma, neurologic diseases, obesity and cardiovascular disease [44. Data from the 2010-2011 through 2022-2023 flu seasons indicate that between 6,000 and 25,000 flu-related hospitalizations occur among children aged five years and younger each year ^[44].

Routine childhood immunization schedules recommend one annual dose of influenza vaccination for all children 6 months of age and older, however, there are some circumstances where children 6 months to 8 years should receive two doses ^{[1,2,3, 45]}. The influenza vaccine is associated with reductions in influenza cases, flu-associated health care utilization, flu-related deaths and missed school days ^[44]. A 2023 study estimated that the incremental cost-effectiveness ratio of the influenza vaccine was approximately $95,000 per quality-adjusted life year (QALY) for all age and risk groups except for non-high risk adults 18–49 ^[46].

Historical Results – National Averages