Introduction
Pediatric immunizations are a critical component of healthcare in the United States. They are responsible for the reducing the occurrence of dangerous and deadly vaccine-preventable infections in the US. Vaccines are suspensions of biological organisms, toxins, or surface proteins that stimulate an immune response by imitating pathogens that lead to dangerous infections. Vaccines do not lead to infections themselves, because the pathogens that compose them are incomplete, weakened, or dead. The immune system commits these pathogens to memory so that future encounters will lead to a fast and efficient immune response that diminishes disease symptoms and course in the host.
Today, the CDC provides a well-spaced immunization schedule that protects children from common, dangerous infections before they are likely to be exposed. All 50 states require proof of immunizations for children to enter daycare and school, promoting widespread immunization. All states also provide medical exemptions for those who have medical contraindications to vaccines, and most states allow nonmedical exemptions for religious or philosophical beliefs.
By following the immunization schedule, parents not only protect their children, but also protect other children and adults who cannot receive immunizations due to age or medical contraindication. This is accomplished through herd immunity, in which an unvaccinated person is indirectly protected from disease by the immunization status of the population around them {Fine:2011fj}. Some parents decide against vaccinating their children, leaving them at risk for these infections. It is essential for healthcare providers and parents to discuss the critical health benefits of vaccines early so that children can continue to enjoy the preventive advantages afforded by these immunizations.
Scope of the Problem
Childhood immunizations have long been used as a safe and effective way to prevent numerous infections. The current immunization schedule protects children against hepatitis B, diphtheria, tetanus, pertussis, rotavirus, Haemophilus influenza type b (Hib), polio, pneumococcus, measles, mumps, rubella, hepatitis A, varicella, meningococcus, influenza, and human papilloma virus. Some of these infections are extremely dangerous or even deadly, and childhood immunizations have significantly reduced their prevalence.
As of 2007, cases and deaths due to hepatitis A and B, Hib, and varicella have experienced at least 80% decline since the pre-vaccination era. Cases and deaths due to diphtheria, mumps, pertussis, and tetanus have experiences 92% and 99% decline, respectively, since the pre-vaccination era {Roush:2007dc}. Despite these powerful data, some parents choose not to vaccinate their children, and will delay immunizations or request non-medical exemptions from state-mandated immunization schedules. This can be dangerous not only for their children, but for others around them who are not protected against infection.
There are several reasons why an individual may not be protected against these infections. Each vaccine has a minimum age at which it can be administered, leaving those younger than that age susceptible. Additionally, immunocompromised individuals cannot receive some vaccines because their weakened immune system puts them at risk of contracting the infection. Also at risk are individual who do not have a sufficient immunological response to a vaccine. Vaccine efficacy can also dwindle with time, so individuals who have been vaccinated many years prior can become susceptible later in life. While vaccines have an extremely high success rate, there is always the potential for them to be less than 100% effective, leaving a small population of vaccinated individuals defenseless. These individuals who remain susceptible to infection rely on the vaccination status of those around them for immunity. This herd immunity increases protection for entire populations, as long as enough individuals are immunized to maintain a threshold {Fine:2011fj}. Herd immunity has significantly contributed to reducing or eliminating several vaccine-preventable infections, benefiting not only the vaccinated individuals but entire communities {Omer:2009ic}.
Immunization programs, such as state mandates, in the US and other developed countries have significantly reduced the occurrence of these infections. However, outbreaks in the US of vaccine-preventable infections such as measles and pertussis have been reported (XYZ https://www.cdc.gov/measles/cases-outbreaks.html, https://www.cdc.gov/pertussis/outbreaks/trends.html). Studies of these outbreaks have demonstrated that many infected children were intentionally not vaccinated XYZ.
Measles are reported as eliminated in the US since 2000, however other parts of the world still struggle with this disease (XYZ https://www.cdc.gov/measles/about/faqs.html#still-get-it), and foreign travelers can bring cases of measles into the US. Between 2000-2016, 1416 measles cases were reported in publications and outbreak reports, and 56.8% of those individuals were unvaccinated against measles. Of those unvaccinated individuals, 70.6% had nonmedical exemptions {Phadke:2016dr}. Salmon et al. reports that individuals with vaccine exemptions are at 35 times greater risk of developing measles than the vaccinated population {Salmon:1999vq}. Measles incidence is greater in communities with higher rates of vaccine exemption. In many cases, nonmedical exemptions occur in clusters, leaving that entire community at higher risk of measles outbreak in exempt and nonexempt individuals (move to prevalence section).
Pertussis, unlike measles, still exists in the US. Whole-cell pertussis vaccines were incorporated into the childhood immunization schedule in the 1940’s, and thereafter pertussis cases saw a steady decline until 1976. Since then, pertussis incidence has steadily increased to more than 25,000 cases annually. Several factors contribute to this increase in incidence. The original, whole-cell pertussis vaccine was more effective than the current acellular vaccine that is administered {Anonymous:1997uz}. The acellular vaccine is reported to have less adverse reactions than its whole-cell predecessor {Decker:1995tt}. It has been reported that immunity to pertussis wanes following vaccination, leaving individuals more susceptible as time increases from their last pertussis vaccination {Klein:2012ce}. However, even in the presence of these factors, nonmedical exemption from pertussis vaccination continues to play a role in pertussis outbreaks across the US {Imdad:2013bg, Atwell:2013dm, Feikin:2000ue, Omer:2008eb}.
The dangerous decision to obtain a vaccine exemption stems from various reasons, including distrust in the government or healthcare industry or fear of side effects. Individuals with strong anti-vaccine mentalities, dubbed ‘anti-vaxxers,’ are prominent throughout the US for their belief that vaccines can lead to autism and other disorders. This falsehood began in 1998 when the former Dr. Andrew Wakefield and colleagues published a paper in the Lancet associating the MMR vaccine with behavioral deterioration and other developmental disorders {Wakefield:1998ws}.
The paper was later discredited and retracted, stating that the data (n=12) were insufficient, and a causal link between the MMR vaccine and autism was not supported {Murch:2004hq, Eggertson:2010kd}. Mr. Wakefield was later stripped of his medical license for ethical violations and failure to disclose that he his funding had ties to anti-vaccine lawsuits. Vaccine rates began to decline following the publication. Despite numerous peer-reviewed publications refuting a link between MMR and autism {Dales:2001wa, Taylor:1999vb}, the anti-vaxxer movement remains, and Mr. Wakefield continues to be celebrated by the anti-vaxxers. Healthcare professionals should encourage proper immunization by actively addressing these concerns or false beliefs and assuring that any misinformation is swiftly corrected {Smailbegovic:2003wi}.
Etiology/Prevalence/Course
Vaccine-preventable infections can be caused by both virus and bacterium. Each infection has a unique prevalence and course that distinguish it from others. Some are not as easily identified, and others are notorious for distinct signs and symptoms that assist clinicians in their diagnosis and treatment.
Measles only affects humans and is caused by a paramyxovirus. In the US, the measles were declared eradicated in 2000 as a result of successful immunization programs. Outbreaks still occur, with 70 cases throughout 16 states reported in 2016 (XYZ https://www.cdc.gov/measles/cases-outbreaks.html). Many of these cases occurred due to foreign travelers who transmit the infection to unvaccinated individuals. It is transmitted by either large or aerosolized droplets from coughing. With an incubation period of 7-14 days, measles leads to a prodrome of fever, coryza, hacking cough, and conjunctivitis. Clustered white spots on the buccal mucosa, known as Koplik spots, are pathognomonic and appear 1-2 days before the rash. The maculopapular rash begins on the face and neck and spreads to the trunk and extremities within 1-2 days. Palms and soles are not spared, and symptoms can last for 9-11 days. It is an extremely contagious infection that can be transmitted days before and after the rash appears. Infection with measles can lead to several severe complications, including otitis media, pneumonia, encephalitis, hepatitis, and subacute sclerosing panencephalitis (XYZ http://www.merckmanuals.com/professional/pediatrics/miscellaneous-viral-infections-in-infants-and-children/measles).
Pertussis, commonly called whooping cough, is a highly contagious acute respiratory infection caused by the Bordatella pertussis bacteria. While pertussis remains endemic in the US, incidence has decreased more than 75% since the pre-vaccine era. Transmission is achieved through aerosols of the bacteria during the early stages of infection. Pertussis has an incubation period of 7-14 days. Symptoms include wheezing, coryza, and hacking cough that becomes more severe and intense over time. Consecutive, forceful coughs repeat themselves during a single inspiration followed by a hurried, deep inspiration. Infants may experience choking spells. Complications include otitis media and bronchopneumonia. The infection lasts approximately 7 weeks, with symptoms diminishing usually within 4 weeks. However, the paroxysmal cough may recur for months.
Hepatitis A and B are infections of the liver caused by the hepatitis A and B viruses, respectively. Hepatitis A and B viruses lead to approximately 3000 cases each of viral hepatitis annually in the US. Incidence has decreased from 25,000 cases/year each prior to the availability of vaccination. Hepatitis A is spread by fecal-oral route. Transmission of hepatitis B is through blood or bodily fluids, and delivery poses a 70-90% risk to infants born to infected mothers. Most children infected by hepatitis A are asymptomatic. Symptomatic children may experience fever, anorexia, malaise, nausea, and vomiting. Jaundice is rare in children less than 6 years old (XYZ http://www.merckmanuals.com/professional/hepatic-and-biliary-disorders/hepatitis/hepatitis-a,-acute). Disease caused by hepatitis B can range from a carrier state without symptoms to severe, fulminant hepatitis. Typical symptoms can last weeks to 6 months, and include nausea, vomiting, fever, and jaundice. Disease in infected infants can progress to chronic infection, cirrhosis, or hepatocellular carcinoma (XYZ http://www.merckmanuals.com/professional/hepatic-and-biliary-disorders/hepatitis/hepatitis-b,-acute).
Chickenpox, caused by the varicella zoster virus, is an acute systemic pediatric infection.
Treatment/Interventions
Immunization against measles is the most effective preventive measure for this infection. The measles vaccine also includes vaccination against mumps and rubella. It is a 2-dose series administered at 12-15 months and 4-6 years of age. As there is no antiviral therapy for measles, it is treated with supportive care to relieve symptoms and address any complications. Individuals with severe infection requiring hospitalization should be approached with airborne precautions. Vitamin A can be administered for severe cases and corrects low levels of vitamin A that can be induced by the infection (XYZ https://www.cdc.gov/vaccines/hcp/vis/vis-statements/mmr.html, https://www.cdc.gov/measles/hcp/index.html).
Similar to measles, immunization is the most effective preventive measure for pertussis. The DTaP vaccine protects against diphtheria, tetanus, and pertussis, and is administered at 2, 4, 6, and 15-18 months and 4-6 years of age. Older children and adults received the Tdap vaccine instead (XYZ https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolescent.html). Pertussis is treated with supportive care and either erythromycin or azithromycin during the catarrhal stage. Once the paroxysmal cough begins, antibiotics are no longer effective. Trimethoprim/sulfamethoxazole can be substituted in patients greater than 2 months of age who are intolerant of macrolides (XYZ http://www.merckmanuals.com/professional/infectious-diseases/gram-negative-bacilli/pertussis).
Hepatitis A is treated supportively. Hepatitis A vaccine is administered in a 2-dose series between 12-23 months. The doses should be separated by 6-18 months (XYZ CDC schedule). For infants born to infected mothers, immediate treatment with hepatitis B immunoglobulin and vaccination can prevent infection. The hepatitis B vaccine is administered in a series. It is typically the 1st vaccination received, administered at birth, 1-2, and 6-18 months (XYZ CDC schedule). Pediatric patients with chronic hepatitis can be treated with interferon,
References
While these immunizations are not 100% effective, most of them produce immunity in more than 90% of patients, greatly reducing the risk of infection (XYZ, vaccine.org vaccines are effective). Throughout history, when any vaccine is licensed, cases of the disease targeted by that vaccine experiences a significant decline. Because this decline correlates with vaccine licensure, declines in infections are attributed to the immunization and not an increase in hygiene.
Side effects cause concern in many parents. While vaccines can lead to some side effects, they are often mild and brief. It is important to remind parents that most patients who receive immunizations do not experience side effects. The most common side effects include reactions at the injection site, mild fever, headaches, and muscle or joint pain. Parents can be reassured that vaccine development is an extensive and widely regulated process, resulting in a safe product for their child. A vaccine can be licensed only after the successful completion of three standardized phases of clinical trials in which efficacy, safety, dosing, and side effects are all evaluated. Even after licensure, monitoring continues through the US Food and Drug Administration (FDA), Center for Disease Control (CDC), other federal agencies, and further clinical trials {Roush:2007dc}.
Socioeconomic status may also play a role in under-immunization. While parents with little or no health insurance may feel disadvantaged, the Vaccines for Children (VFC) Program is available for assistance. The VFC Program is federally funded, providing free vaccines for children who otherwise would not receive them. Through the VFC, physicians receive vaccines at no charge and in turn administer them to eligible patients at no cost. Ensuring that parents are informed about the VFC Program increases access to these immunizations to all children.
There is also a growing movement of distrust in the government and healthcare, leading to an anti-vaccination movement {Lee:2016dz}. Informally known as the ‘anti-vaxxers,’ these parents
During development, adjuvants are incorporated into some vaccines. Adjuvants are substances that increases the intensity and duration of the immune response {Pulendran:2006ky}. Controversy has arisen over the inclusion of some adjuvants, particularly aluminum due to its association with neurotoxicity. Several publications support the safety of including these adjuvants {Keith:2002uq, Mitkus:2011gz}. Furthermore, it has been calculated that the aluminum delivered in all recommended immunizations for 0-12 month old children is equivalent to approximately 1 liter of baby formula, an amount that is much less than toxic thresholds.