A Parents’ Primer on Vaccines

Mar 28, 2024 | Children's Health

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Vaccines are an important part of keeping our children healthy as they grow. 

Whether you’re navigating the world of immunizations for the first time or just need a refresher, Brett Hutchinson, MD, Board Certified pediatrician with Our Lady of the Lake Children’s Health, shares details about the vaccines parents need to know about to protect kids from preventable diseases. 

Download our guide to Wellness Checks from Newborn to Teenage Years with a complete vaccine schedule designed to know which vaccines you can expect at each visit. 

Dr. Hutchinson is a guest on our ParentingU podcast talking about all things vaccines for tweens and teens.

Diphtheria Tetanus Pertussis Vaccine (DTaP, Tdap)

Vaccines for diphtheria were first introduced in the 1920s, and the implementation of universal childhood immunization occurred in the late 1940s.

Diphtheria is an acute, bacterial disease caused by toxin-producing strains of Corynebacterium diphtheriae. Early symptoms include malaise, sore throat, loss of appetite and low-grade fever. Within two to three days, a bluish-white membrane forms on the throat and tonsils and extends, varying in size from covering a small patch on the tonsils to covering most of the soft palate. The membrane eventually turns greyish-green or, if bleeding has occurred, black. The membrane is firmly adherent to the tissue, and forcible attempts to remove it cause bleeding. Extensive membrane formation may result in respiratory obstruction and death.

Diphtheria is now rarely reported in the U.S.; however, in the pre-vaccine era, the disease was one of the most common and feared causes of illness and death among children. Widespread use of diphtheria vaccines has contributed to the control of diphtheria in the U.S. with the last major outbreak occurring in the 1970s.

The first tetanus vaccines were introduced in the late 1940s.

Tetanus is an acute, often fatal, disease caused by the bacterium Clostridium tetani. It is characterized by generalized rigidity and convulsive spasms of skeletal muscles. The muscle stiffness usually begins in the jaw (lockjaw) and neck and then becomes generalized. 

Tetanus occurs worldwide. The bacteria usually enter the body through contaminated wounds (apparent and inapparent). The wound may be major or minor. Tetanus may follow elective surgery, burns, deep puncture wounds, crush wounds, otitis media, dental infection and animal bites.

After the development of the vaccine in the 1940s, reported tetanus incidence rates declined steadily. Since the mid-1970s, about 50 to 100 cases have been reported annually in the U.S. More recently, from 2009 to 2018, an average of 29 cases were reported per year.

Pertussis vaccines were first routinely used in the 1940s and were available as a combined vaccine with diphtheria and tetanus in 1948.

Pertussis, more commonly known as whooping cough, is a contagious respiratory disease caused by the bacterium Bordetella pertussis. The illness is typically characterized by a prolonged cough often accompanied by a whoop. Infants are at greatest risk for pertussis-related complications and death. Pneumonia is the most common complication. Neurologic complications, such as seizures and encephalopathy, are rarer but may occur as a result of hypoxia from coughing.

In the 20th century, pertussis was one of the most common childhood diseases and a major cause of childhood death in the U.S. Before the availability of pertussis vaccines in the 1940s, more than 200,000 cases of pertussis were reported annually. Following the use of the vaccine, pertussis incidence gradually declined, reaching and average of 2,900 cases per year between 1980 and 1990. Pertussis incidence has been gradually increasing in the U.S. since then, leading to the vaccination of adolescents and adults. 

Polio Vaccine (IPV)

Vaccines for polio were first introduced in 1955.

Poliomyelitis is a highly contagious disease caused by polioviruses. Infection with poliovirus results in a spectrum of presentations from inapparent infection to nonspecific febrile illness, aseptic meningitis, paralytic disease and death.

Poliomyelitis became an epidemic disease in the U.S. at the turn of the 20th century. Epidemics of ever-increasing magnitude occurred, with more than 20,000 cases of poliomyelitis with permanent paralysis reported in 1952. Following the introduction of effective vaccines in 1955, the reported incidence of poliomyelitis in the U.S. declined dramatically to less than 100 cases in 1965 and to less than 10 cases in 1973.

Haemophilus Influenzae Vaccine (Hib)

The first Hib vaccines were introduced in 1985.

Haemophilus influenzae invasive disease is caused by the bacterium Haemophilus influenzae. Invasive H. influenzae diseases include clinical syndromes of meningitis, bacteremia or sepsis, epiglottitis, pneumonia, septic arthritis, osteomyelitis, pericarditis and cellulitis. Diseases considered noninvasive include bronchitis, sinusitis and otitis media. 

Before the introduction of effective vaccines, H. influenzae serotype b (Hib) was the cause of more than 95% of cases of invasive H. influenzae disease among children younger than 5. Approximately 1 in 200 children developed invasive Hib disease. Approximately two-thirds of all cases occurred among children younger than 18 months old. Hib was the leading cause of bacterial meningitis in the U.S. among children younger than 5 and a major cause of other life-threatening invasive bacterial diseases in this age group. Meningitis occurred in approximately two-thirds of children with invasive Hib disease, resulting in hearing impairment or severe permanent neurologic complications, such as seizure disorder, cognitive and developmental delay, and paralysis in 15% to 30% of survivors. Approximately 4% of all cases were fatal. 

Since the introduction of Hib vaccines in 1985, the incidence of invasive Hib disease in children younger than 5 has decreased by 99%, to less than 1 case per 100,000 in children younger than 5.

Streptococcus Pneumoniae Vaccine (PCV)

The first pneumococcal vaccine was introduced in 1977, and routine use of pneumococcal vaccines began in 2000.

Streptococcus pneumoniae (pneumococcus) is a bacterium with more than 90 known types. Although all types can cause serious disease, a relatively limited number of types cause the majority of severe disease. Pneumococcus is spread by airborne droplets and is a leading cause of serious illness, including bacteremia, meningitis, and pneumonia among children and adults worldwide. It is also one of the common causes of ear infections and sinusitis. 

With the decline of invasive Haemophilus influenzae type b (Hib) disease due to vaccination, pneumococcus has become the leading cause of bacterial meningitis among children younger than age 5 in the U.S. Children younger than 1 had the highest rates prior to routine use of the pneumococcal vaccine. 150,000 hospitalizations from pneumococcal pneumonia are estimated to occur annually in the U.S. Pneumococcus is the most common bacterial cause of childhood pneumonia, especially in children younger than 5.

Efforts to develop effective pneumococcal vaccines began as early as 1911. However, with the advent of penicillin in the 1940s, interest in pneumococcal vaccination declined until it was observed that many patients still died despite antibiotic treatment. By the late 1960s, efforts were again being made to develop a pneumococcal vaccine. The first pneumococcal vaccine was licensed for use in the U.S. in 1977. Improved versions of the vaccine have been in use since 2000. By 2007 serious illness due to the pneumococcal types included in the vaccine declined by 99%, to less than 1 case per 100,000 in children younger than 5. 

Rotavirus Vaccine (RV5)

Current rotavirus vaccines have been in use since 2006.

Rotavirus is a family of viruses that by 1980 was recognized as the most common cause of severe gastroenteritis in infants and young children in the U.S. Rotavirus infection in infants and young children can lead to severe diarrhea, dehydration, and electrolyte imbalance.

Before the advent of rotavirus vaccines, an estimated 2.7 million rotavirus infections occurred every year in the U.S., and 95% of children experienced at least one rotavirus infection by age 5 years. Rotavirus infection was responsible for 410,000 physician visits, more than 200,000 emergency department visits, 55,000 to 70,000 hospitalizations, and 20 to 60 deaths annually in children younger than age 5 years. Rotavirus accounted for 30% to 50% of all hospitalizations for gastroenteritis among children younger than age 5, highest among children 3 months to 35 months old.

After introduction of the current vaccine in 2006, it was estimated that an average annual 280,000 clinic visits, 62,000 emergency department visits and 45,000 hospitalizations for rotavirus disease were averted among U.S. children younger than 5 during the period of 2007 to 2011.

Varicella Vaccine (VAR)

Varicella vaccine was introduced in Japan and Korea in 1988 and in the U.S. in 1995. 

Varicella (chickenpox) is a febrile rash illness resulting from primary infection with the varicella-zoster virus (VZV). Humans are the only source of infection for this virus. Varicella is highly infectious, with infection spreading to nearly 100% of susceptible household contacts.

Varicella severity and complications are increased among immunocompromised persons, pregnant women, children younger than 1 and adults. However, healthy children can also develop serious complications and even die from chicken pox. The virus remains in an inactivated state in human nerve tissue and reactivates in approximately one in three infected persons during their lifetime, resulting in herpes zoster (shingles).

Before the availability of varicella vaccine in the U.S., almost everyone had varicella. Therefore, by the early 1990s (the pre-vaccine era), this resulted in an average of 4 million cases of varicella, 10,500 to 13,000 hospitalizations (one to two per 1,000 cases among healthy children), and 100 to 150 deaths each year. Varicella primarily affected children, with approximately 90% of cases occurring before age 15.

Since implementation of the varicella vaccination program in 1996, the number of cases is estimated to have declined by 97%. 

Measles Mumps Rubella Vaccine (MMR)

The fist measles vaccine was introduced in 1963, and the combined MMR vaccine was introduced in 1971. 

Measles is an acute viral illness caused by a virus in the family Morbillivirus. Measles is characterized by a period of fever (as high as 105°F) and malaise, cough, runny nose and conjunctivitis, followed by a rash. The rash spreads from head to trunk to lower extremities. Measles is usually a mild or moderately severe illness. However, measles can result in complications such as pneumonia, encephalitis, and death. Approximately one case of encephalitis and two to three deaths may occur for every 1,000 reported measles cases.

Before a vaccine was available, infection with measles virus was nearly universal during childhood. More than 50% of persons had measles by age 6, and more than 90% by age 15. In the U.S. before 1963, approximately 500,000 cases and 500 measles deaths were reported annually, with epidemics every two to three years. However, the actual number of cases was estimated at 3 to 4 million annually. In the years following licensure of vaccine in 1963, the incidence of measles decreased by more than 95%.

Although measles elimination has been achieved in the U.S., importation of measles will continue to occur as measles remains endemic in many other parts of the world. The World Health Organization estimates there were 142,300 deaths from measles globally in 2018. In the U.S., there have been recent outbreaks; the largest occurring in 2019, primarily among people who were not vaccinated.

Mumps vaccine was introduced in the U.S. in 1967. MMR in 1971. 

Mumps is an acute viral illness caused by a paramyxovirus that typically presents as swelling of the parotid (parotitis) or other salivary glands. Symptoms may precede parotitis by several days, including low grade fever, which may last three to four days, muscle aches, loss of appetite, malaise and headache.

The most common complications of mumps include inflammation of the testicles, inflammation of the ovaries, mastitis, pancreatitis, hearing loss, meningitis and encephalitis. 

In the pre-vaccine era, mumps was a universal childhood disease, with the highest incidence among children 5 to 9. Well over 100,000 cases were reported annually. Permanent unilateral deafness caused by mumps occurred in one of every 20,000 infected people.

Following the introduction of mumps vaccine, reported cases of mumps steadily decreased from over 152,000 cases in 1968 to 2,982 in 1985. By the early 2000s, reported mumps cases declined to an average of less than 300 cases annually. Worldwide, mumps is not as well controlled as measles and rubella.

Rubella vaccine was introduced in 1969. MMR in 1971. 

Rubella is a viral illness caused by a virus called Rubivirus and is characterized by a mild flat to raised rash. When rubella infection occurs during pregnancy, especially during the first trimester, serious consequences can result. These include miscarriages, fetal deaths/stillbirths and a constellation of severe birth defects known as congenital rubella syndrome (CRS). The most common congenital defects are cataracts, heart defects and hearing impairment.

Before the availability of rubella vaccines in the U.S., rubella was a common disease that occurred primarily among young children. Incidence was highest during the spring with epidemics every six to nine years. The last major epidemic in the U.S. occurred from 1964 to 1965, when there were an estimated 12.5 million rubella cases in the U.S., resulting in 2,000 cases of encephalitis, 11,250 therapeutic or spontaneous abortions, 2,100 neonatal deaths, and 20,000 infants born with CRS.

Following vaccine introduction in 1969, rubella incidence declined dramatically. Rubella outbreaks continued to occur among adolescents and young adults and in settings where unvaccinated adults gathered. In 2004, endemic rubella was declared eliminated in the U.S., with fewer than 10 cases reported annually and less than one CRS case per year. However, it continues to be endemic in many parts of the world. It is estimated that more than 100,000 infants worldwide are born annually with CRS.

Hepatitis B vaccine (HepB)

The first hepatitis B vaccine was introduced in 1982. 

Hepatitis B is caused by infection with the hepatitis B virus (HBV) and results in both acute and chronic liver disease. It is predominantly a blood and sexually transmitted infection, but saliva has also been demonstrated to contain the virus in infected persons. Symptoms can include loss of appetite, malaise, nausea, vomiting, abdominal pain, jaundice, dark urine, skin rashes, arthritis and others. Although the consequences of acute hepatitis B can be severe, most of the serious complications occur in persons in whom chronic infection develops. Chronic liver disease develops in two-thirds of these persons, and approximately 15%–25% die prematurely from cirrhosis or liver cancer. In infants, young children, and immunosuppressed persons, most newly acquired HBV infections result in chronic infection. Infants are at greatest risk, with a 90% chance of developing chronic infection if infected at birth.

Until recently, hepatitis B was one of the most frequently reported vaccine-preventable diseases in the U.S., with 15,000 to 20,000 new cases reported annually. Since the hepatitis B vaccines were licensed in the U.S. in 1982, the number of acute HBV infections has declined to one per 100,000 people in 2016.

Hepatitis A vaccine (HepA)

Hepatitis A vaccine was introduced in 1995. 

Hepatitis A is caused by infection with hepatitis A virus (HAV). The clinical course of hepatitis A is indistinguishable from that of other types of acute viral hepatitis. The illness typically causes an abrupt onset of fever, malaise, loss of appetite, nausea, abdominal discomfort, dark urine and jaundice. Though rare, liver failure can occur. 

Illness usually does not last longer than 2 months, although 10% to 15% of persons have prolonged or relapsing signs and symptoms for up to 6 months. The likelihood of symptomatic illness from HAV infection is directly related to age. In children younger than 6, up to 70% of infections are asymptomatic. In older children and adults, infection is usually symptomatic, with jaundice occurring in more than 70% of patients. Because children generally have asymptomatic or unrecognized illnesses, they may serve as a source of infection, particularly for household or other close contacts.

Prior to 2004, hepatitis A was the most frequently reported type of hepatitis in the U.S. Historically, children ages 2 through 18 years had the highest rates of hepatitis A. Since the introduction of the vaccine in 1995, and due in large part to eventual inclusion in the routine childhood vaccination schedule nationwide, hepatitis A rates in the U.S. had declined by more than 96% by 2014.

Meningococcal meningitis vaccine (MenACWY, MenB)

The first meningococcal vaccine was introduced in 1978. The current meningococcal vaccines were introduced in 2005.

Meningococcal disease is an acute, severe, potentially life-threatening infection caused by the bacterium Neisseria meningitidis. It is a leading cause of bacterial meningitis and sepsis in the U.S. It can also cause diseases such as pneumonia and septic arthritis. Signs and symptoms of meningococcal disease include sudden onset of high fever, neck stiffness, confusion, nausea, vomiting, lethargy and/or a distinctive rash. Without prompt and appropriate treatment, the infection can progress rapidly and result in death. 

The use of antibiotics has dramatically reduced deaths due to meningococcal disease. However, even with prompt and appropriate antimicrobial treatment, the fatality rate remains 10% to 15%, and may be as high as 40% in some cases. Of those who survive invasive disease, 10% to 20% experience complications, including limb loss, extensive skin scarring, neurosensory hearing loss, mild to moderate cognitive defects, or seizure disorders.

The incidence of meningococcal disease has been steadily declining in the U.S. since the late 1990s. During 2015 to 2017, the incidence of meningococcal disease was less than 1 case per 100,000 in the U.S.

Human Papillomavirus vaccine (HPV9)

HPV vaccine was introduced in 2006. 

Genital human papillomavirus (HPV) is the most common sexually transmitted infection in the U.S.. Although the majority of HPV infections cause no symptoms and are self-limited, persistent HPV infection can cause cervical cancer in women as well as other anogenital (anal, vaginal, vulvar, penile) cancers, throat and neck cancers, and genital warts in men and women.

On average, nearly 44,000 HPV-associated cancers are reported annually, including over 24,000 in females and over 19,000 in males. In addition to 91% of cervical cancer, HPV is responsible for about 91% of anal cancers, 69% of vulvar cancers, 75% of vaginal cancers, 63% of penile cancers and 70% of throat and neck cancers. 

Based on data from 2003-2006 (before vaccine introduction), an estimated 79 million people were infected in the U.S. Approximately 14 million new HPV infections occurred annually, with nearly half occurring people 15 to 24. Within a decade of the introduction of the first HPV vaccine in 2006, prevalence of the strains included in that vaccine decreased 86% among females aged 14 through 19 years and decreased 71% among females aged 20 through 24 years.

A strong relationship with your pediatrician is important throughout your parenting journey, including making sure your child gets the vaccines they need at the right time. 

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