Background
Recent infectious disease outbreaks like the 2014 and 2015 measles outbreak in California demonstrate the risks of vaccine-preventable disease outbreaks related to under-immunized populations. Of the 125 victims of the measles outbreak, 49 were unimmunized including 12 infants who were too young to be vaccinated. The incident has called upon health care providers to promote higher rates of immunization in order to improve herd immunity and protect those who are unable to be vaccinated due to age, allergies, or other medical conditions. In addition, the resurgence of other vaccine-preventable diseases including pertussis and mumps in the United States has raised national attention to promote improving immunization rates and herd immunity (Ward, Flowers, Gansler, Omer, & Bednarczyk, 2017). Herd immunity occurs as a result of when a significant portion of a population develops immunity to a specific disease through acquired active immunity from either previous infection or prophylactic immunization. Widespread use of immunizations reduces the number of vaccine-preventable diseases and the spread of the microorganisms that cause them. As more individuals refuse vaccinations, the herd immunity is weakened, and more people are exposed to and suffer from vaccine preventable diseases (Meissner, 2015).
As a result, there have been several initiatives to increase vaccine rates. The World Health Organization (WHO) and 2011-2020 Global Vaccine Action Plan (GVAP) aims to promote access to vaccines and prevent morbidity and mortality of vaccine-preventable diseases by improving routine immunizations, developing new vaccinations, and introducing more effective vaccines to all people (Doherty, Schmidt-Ott, Santos, Stanberry, Hofstetter, Rosenthal, & Cunningham, 2016). The GVAP has identified some patient populations who often have lower immunization rates and are at an increased risk of acquiring vaccine-preventable diseases including preterm infants, pregnant women, and immunocompromised patients (Doherty et al., 2016). The most influential factors of vaccination rates include the attitude of health care providers towards immunization, fear of adverse outcomes related to the vaccines, and lack of awareness about current immunization recommendations among these patient populations. It is essential that pediatric health care providers confidently discuss the risks, benefits, and effectiveness of vaccines with patients and their caregivers. Common fears associated with immunizations include misconceptions about the safety profile, ingredients, side effects, long term health effects, and behavioral concerns associated with vaccines. Due to the number of unvalidated sources of information about vaccines, it is critical that health care providers recommend that patients and their caregivers use evidence-based references when researching information about the safety and effectiveness of immunizations (Doherty et al., 2016).
Immunocompromised pediatric oncology patients are at an especially high risk of acquiring vaccine-preventable diseases. During chemotherapy treatment, the recommended childhood immunization schedule is often delayed or interrupted due to neutropenia and the inability to receive live vaccines like the MMR vaccine. In addition, the humoral and cellular immunity that the patient may have developed from vaccines prior to chemotherapy is often depressed, which can lead to subtherapeutic antibody titers, so children may receive a booster dose of all previously administered vaccines. Inactivated or recombinant vaccines may be administered 3 months after the completion of chemotherapy and live attenuated vaccines may be given 6 months post-chemotherapy. Pediatric oncology patients are recommended to receive an annual inactivated flu vaccine despite chemotherapy status due to the high risk of morbidity and mortality associated with influenza (Ward et al., 2017).
Influenza is one of the vaccine-preventable diseases that is significantly associated with morbidity, mortality, and health care expenditure among pediatric oncology patients (Kotecha et al., 2016). The majority of pediatric oncology patients who contract influenza are hospitalized with complications that may include pneumonia, respiratory failure, and a need for ventilator support. These complications can result in chemotherapy treatment delays of 3 weeks on average, which can affect their long-term prognosis including chance of remission and relapse (Ward et al., 2017). Despite the recommendation to administer annual inactivated influenza immunizations to pediatric oncology patients, one-third of pediatric oncologists do not prescribe the yearly influenza vaccine (Kotecha et al., 2016). Poor compliance with influenza vaccination among pediatric oncology patients has been due to lack of knowledge and the absence of literature supporting the immune response to vaccination (Kotecha et al., 2016). In addition, the fear of adverse outcomes has prevented provider compliance with annual influenza vaccination recommendations (Doherty et al., 2016).
Discussion
Studies have evaluated the immunogenicity and clinical effectiveness of the trivalent inactivated influenza vaccine among pediatric oncology patients who were 6 months to 18 years old and were receiving or within 4 weeks from completion of immunosuppressive therapy. Children who had a history of anaphylaxis to previous influenza vaccines, history of egg anaphylaxis, receipt of intravenous immunoglobulin within the last 3 months, a neutrophil count of ≤0.5 x 109/L, a history of Guillain-Barre syndrome and children having undergone autologous stem cell rescue or allogenic hematopoietic stem cell transplant were excluded from the studies (Kotecha et al., 2016).
Children with solid tumors had higher rates of seroconversion after the influenza vaccine than hematological malignancies due to adverse effects of hematological malignancies on the immune system. Oftentimes, hematological malignancies are treated with continuous myelosuppression therapy as compared to solid tumors are treated with shorter, more cyclical immunosuppression therapy. The continuous chemotherapy-induced immunosuppression among hematological malignancies accounts for the decreased seroconversion rates among these patients. Although seroconversion among hematological malignancies may not be statistically significant, the benefit of influenza prevention supports the recommendation to continue to administer influenza vaccines among all pediatric oncology patients (Kotecha et al., 2016).
Those with a normal lymphocyte count at time of vaccination were more likely to serorespond to the influenza vaccine as compared to those with lower lymphocyte counts, as evidenced by the patients receiving low intensity chemotherapy were significantly more likely to serorespond than those who are receiving high-intensity chemotherapy. As a result, the timing of the influenza vaccination should be individually tailored based on the lymphocyte counts and IgG levels. Providers may use clinical judgement to determine the timing of the influenza vaccine, because immunization should not be delayed due to suboptimal lymphocyte counts or IgG levels (Kotecha et al., 2016).
Children less than 10 years old were significantly more likely to serorespond with 2 doses of influenza vaccine despite history of being vaccinated in previous influenza seasons. Although the results may not provide statistical significance supporting the efficacy of yearly influenza immunizations, the studies demonstrate that the vaccines are immunogenic and provide clinical protection for pediatric patients undergoing immunosuppressive oncology treatment (Kotecha et al., 2016).
Overall, the trivalent inactivated influenza vaccine has been proven to be clinically effective in pediatric oncology patients with an adjusted estimated vaccine effectiveness of 72% as compared to 82% among healthy children. No vaccine-related serious adverse events were recorded. Of the patients who were studied, 3% developed a fever within 24 hours of receiving the vaccine. Those patients required brief inpatient hospitalizations for empiric antibiotic therapy until they became afebrile. As a result, the influenza vaccine has been proven to be safe (Kotecha et al., 2016).
Recommendations
Pediatric oncology patients undergoing immunosuppressive oncology treatment should receive yearly age-appropriate inactivated influenza vaccinations. Those under 10 years old should receive a second influenza vaccines at least 4 weeks after the first immunization (Kotecha et al., 2016).
In addition, the caregivers of immunosuppressed oncology patients including families and health care providers should also receive inactivated influenza vaccinations. Immunizing the caregivers of immunosuppressed patients further prevents the spread of influenza and protects patients. Should the caregivers of pediatric oncology patients receive a live attenuated influenza vaccine, they should avoid contact with the patient for 7 days after the live vaccine (Ward et al., 2017).
Health care providers, patients, and caregivers should also take preventive actions to avoid the spread of influenza and other contagious diseases. Diligent hand hygiene and covering your mouth and nose when you cough or sneeze can prevent the spread of illnesses. Also, frequently touched surfaces should be cleaned and disinfected frequently, and immunosuppressed patients should avoid people who may be ill with influenza or other contagious infections. Patients and their caregivers should receive prompt medical care if they develop fever, chills, body aches, fatigue, headache, sore throat, runny or stuff nose, cough, vomiting, or diarrhea as they may have the flu. Antiviral medications may be prescribed to minimize the flu symptoms and shorten the duration of the illness if indicated by a health care provider. Antiviral medications are most effective when taken within 48 hours of acquiring the flu (CDC, 2018).
Conclusions
Pediatric oncology patients are at a high risk of acquiring influenza due to their chemotherapy-induced immunosuppression. As a result, the patients, caregivers, and health care providers must take preventative action avoid the spread of influenza to the patient. The inactivated influenza vaccine is recommended for everyone who is at least 6 months of age and does not have a history of a serious reaction to a previous influenza immunization, especially immunocompromised pediatric oncology patients and their caregivers (Ward et al., 2017). Other tactics to prevent the spread of disease include frequent hand washing, covering mouths and noses when coughing or sneezing, avoiding people who may be ill, and disinfecting frequently touched surfaces (CDC, 2018).
Improving health care provider knowledge of vaccines and increasing immunization rates reduces the incidence of vaccine-preventable diseases including the flu. High rates or immunization cause improved herd immunity and decreased morbidity and mortality of vaccine preventable diseases among healthy and immunosuppressed people (Ward et al., 2017). Health care providers should use evidence-based resources to learn more about the vaccines in order to provide informed care to their patients and their families. Patients and their families should be counseled about the risks, benefits, safety profile, and effectiveness of vaccines to provide education and alleviate concerns related to immunizations and the diseases they prevent (Doherty et al., 2016).