Vaccines provide immunity to children before exposure to potentially serious infectious diseases, and play a central role in preventing the spread of diseases with epidemic potential. The schedule for childhood immunizations in the United States (US) is published and routinely updated by the Centers for Disease Control and Prevention (CDC). The childhood vaccine schedule is designed specifically to deliver protection during periods of greatest vulnerability. The schedule includes vaccines of several different types against viral and bacterial infections including hepatitis B, rotavirus, diphtheria, tetanus, pertussis, Haemophilus influenzae type b, pneumococcal disease, polio, influenza, varicella, hepatitis A, measles, mumps, rubella, meningococcal disease, and human papillomavirus. Childhood immunization in the US has been affected by recurring vaccine hesitancy and anti-vaccine activism, including concerns about vaccine safety, vaccine ingredients, and the number and timing of recommended vaccines. Routine childhood vaccination in the US was disrupted during the COVID-19 pandemic, but immunization rates returned to near pre-pandemic levels by 2024. Common adverse reactions to vaccines are usually mild and self-limited, while serious adverse events caused by vaccination are rare. Immunization guidance also identifies precautions and contraindications for children in whom specific vaccines should be delayed or avoided. Among children born in the US between 1994 and 2023, it is estimated that routine childhood vaccinations prevented approximately 508 million illnesses, 32 million hospitalizations, and over 1 million deaths.
Risks and safety monitoring As with all medications, vaccines can cause side effects. The side effects of vaccination are typically minor and go away within a few days. There is a risk that the child could have a severe reaction, but these reactions are rare. However, a decision not to immunize a child also involves risk and could put the child and others who come into contact with him or her at risk of contracting that disease. Many adverse events reported after vaccination are coincidental events that occur after vaccination but are not caused by the vaccine; the timing of an adverse event alone does not establish that vaccination caused the symptoms.
In the US, vaccine safety is monitored through passive reporting systems, linked health databases, and clinical research networks. The National Childhood Vaccine Injury Act of 1986 requires health care providers and vaccine manufacturers to report specified adverse events to the Vaccine Adverse Event Reporting System (VAERS); providers are encouraged to report all clinically important adverse events, even when causality is uncertain. VAERS is used to detect possible safety signals for further investigation, but it is not designed to determine whether a vaccine caused a reported event. Potential safety concerns can be evaluated through other systems, including the CDC's Vaccine Safety Datalink, which uses large linked databases for epidemiologic studies, and Clinical Immunization Safety Assessment Project, which conducts clinical research related to vaccine safety.
Benefits Following the introduction of routine childhood vaccination in the US, reported cases of most vaccine-preventable diseases declined by more than 90%. The CDC estimates that among approximately 117 million children born in the US between 1994 and 2023, routine childhood immunization prevented about 508 million cases of disease, 32 million hospitalizations, and more than 1.1 million premature deaths from vaccine-preventable illnesses, with the number of illnesses averted ranging from roughly 5,000 cases of tetanus to nearly 100 million cases of measles and varicella. The same CDC report estimated "direct savings of $540 billion and societal savings of $2.7 trillion" from these prevented illnesses.
Vaccine compositions Vaccine ExamplesComponentDose (Units)(see key)Dose (μg)References HepB Hepatis virus B 20 Rotarix Rotavirus 1M CCID50 DTaP Diphtheria toxoid 6.7-25 Lf DTaP Tetanus toxoid 5 – 7.5 Lf DTaP aP toxoid 3.2 to 40 DTaP aP filamentous agglutinin 2.5 to 34.4 DTaP aP Pertactin 1.6 to 23.4 DTaP aP fimbriae 2 0.8 to 5 DTaP aP fimbriae 3 5 Haemophilus influenzae type B Hib polysaccharide 10 Streptococcus pneumoniae 13 polysaccharide serotypes (each) 2.2 Polio D antigen 3 types (each) 8-40 Units Influenza Quadrivalent (each) 15 Chickenpox varicella-zoster glycoprotein E 50 HepA Hepatis virus A 720 EL.U MMR Measles 20000 Inf.U MMR Mumps 40000 Inf.U MMR Rubella 8000 Inf.U Meningococcal ACWY A,C,W,Y polysaccharides (each) 4 Meningococcal B NadA, NHBA, fHbp (each) 50 Meningococcal B Outer Membrane Vesicles 25 Human papillomavirus HPV L1 protein 9 types (each) 20 to 60 Key CCID50= cell culture infective dose at 50% IU= international units Lf= Limits of Flocculation (1:1 toxin:antitoxin) Inf.U= Infectious units
Hepatitis B
Hepatitis B is a contagious virus that affects the liver, infection can last from a few weeks to a serious lifelong illness. Two different types of infection exist for this disease, "acute" and "chronic". Acute Hepatitis B is a short-term illness that occurs within 6 months of exposure, Chronic Hepatitis B is long term and happens when the virus remains in the body. The younger the child is, the greater their chance of developing a chronic infection and this risk goes down as the child gets older. Approximately 90% of infected infants will develop a chronic infection.
Vaccine Since 1990, when the vaccine was introduced as a routine vaccination in children, rates of acute Hepatitis B has decreased in the United States by 82%. This vaccine is given as a series of shots, the first dose is given at birth, the second between 1 and 2 months, and the third, and possibly fourth, between 6 and 18 months. Some side effects of this vaccination include: soreness at injection site (1 in 4 children) fever of 99.9 degrees Fahrenheit or higher (1 in 15 children) brief fainting spell Since 1982, when the vaccine became available, more than 100 million people have received the vaccine in the United States and no serious side effects have been reported.
Transmission Hepatitis B is spread in several different ways. It can be passed from mother to child during birth, sex with an infected partner, sharing needles, sharing items such as razors or toothbrushes, or direct contact with the blood or open sores of someone who is infected.
Symptoms Some mild symptoms of Hepatitis B are: fever fatigue loss of appetite abdominal pain dark urine clay colored bowel movements joint pain jaundice (yellow color in skin or eyes) Long term and more severe symptoms include: liver damage, liver failure, liver cancer, and death. Approximately 2,000-4,000 people die every year from Hepatitis related liver disease. Treatment There is currently no medication to treat acute Hepatitis B and those with chronic Hepatitis B need to be monitored regularly for signs of liver disease, and to be evaluated for possible treatment. There are currently a few medications to treat chronic Hepatitis B and new drugs are being researched.
Rotavirus
The rotavirus is most commonly found in infants and young children, but older children and adults can also become infected. Prior to the introduction of the vaccine in 2006, almost all children in the United States became infected with the virus before their 5th birthday. Each year, prior to 2006, rotavirus was responsible for more than 400,000 doctors visits, more than 200,000 emergency room visits, 55,000 to 70,000 hospitalizations, and 20 to 60 deaths in children under the age of 5. Globally, rotavirus is still the cause of approximately half a million deaths each year in children younger than 5 years of age. Unfortunately, there are many strains of rotavirus and the vaccine can not cover all of them, so it is still possible for a child to become infected with rotavirus. Having the illness previously also does not grant immunity, again because there are so many different strains. However, the first infection usually causes the most severe symptoms.
Vaccine This vaccine is a little different in that it is a liquid that is given orally, rather than as an injection. This vaccine is a 2 or 3 dose series, depending on the brand of the vaccine, that is given at 2 and 4 months in the 2 dose series and at 2,4 and 6 months in the 3 dose series. Studies show that this vaccine is 85-98% effective against severe rotavirus disease and is 74-87% effective against rotavirus disease of any severity in the first year after the vaccination.
Side effects of the vaccine include both mild and more severe symptoms
mild: Irritability Mild, temporary diarrhea or vomiting severe: intussusception This is a type of bowel blockage that is treated in a hospital and may require surgery 1 in 20,000 to 1 in 100,000 infants may develop intussusception. If this were to happen, it would occur within a week after the first dose or second dose of the vaccine is given.
Transmission The rotavirus is shed in the feces of infected persons and is spread by the fecal oral route, so this virus can be picked up from contaminated hands, objects, food and water. Children are also able to spread the virus before and after they become sick with diarrhea.
Symptoms Symptoms appear about two days after exposure and include: gastroenteritis (inflammation of the stomach and intestines) fever vomiting severe diarrhea abdominal pain loss of appetite dehydration Vomiting and watery diarrhea may last from 3 to 8 days
Diphtheria, pertussis, and tetanus
DTaP
The DTaP is a combination vaccine that covers three diseases; Diphtheria, Pertussis and Tetanus. The DTaP vaccine is given as a 5-shot series at 2, 4, and 6 months, the fourth between 12 and 15 months, and the last between 4–6 years. A booster is recommended to be given between 11 and 12 years of age and is called Tdap. Some potential side effects of DTaP are mild:
tenderness and redness at the injection site drowsiness, headache, diarrhea, fussiness and low-grade fever uncommon: seizure (1 in 14,000 children) chronic crying last 3 or more hours (1 in 1,000 children) high fever, 105 degrees Fahrenheit or higher (1 in 16,000 children) severe: serious allergic reaction (less than 1 in a million children) long term seizures, coma, or lowered consciousness permanent brain damage
The severe side effects are so rare that it is hard to correlate the vaccine and these symptoms.
Potential side effects of Tdap:
pain, tenderness and redness at injection site headache low fever tiredness nausea
Diphtheria Diphtheria was once a major cause of illness and death among children. In 1921, the U.S. recorded 206,000 cases of diphtheria which resulted in 15,520 deaths. Before the vaccine became widely available in the 1920s, up to half the people that were infected died from this disease. In the past decade, the United States has had fewer than 5 reported cases of diphtheria. Unfortunately, the disease is still an issue globally, with 4,887 cases reported to the World Health Organization (WHO) in 2011.
Transmission Diphtheria is an infection caused by the bacteria Corynebacterium diphtheria. It is spread through respiratory droplets from coughing and sneezing; it can also be spread through skin lesions on the infected person and through contact with contaminated clothes and objects.
Symptoms The bacteria that causes Diphtheria infects the respiratory system, produces a toxin that, within 2 to 3 days, kills tissue that then builds up over the nasal tissues, tonsils, voicebox and throat, in a thick gray coating called a "pseudomembrane", making it very hard to breathe and swallow. The bacteria's toxin also causes the following symptoms: sore throat fever swollen glands in the neck