Varicella (Chickenpox) Vaccine

Mechanism of Action

The varicella-zoster vaccine contains live attenuated varicella-zoster vaccine (Oka strain). This vaccine induces both humoral and cell-mediated immune responses. It produces an IgG humoral immune response in individuals, and the cell-mediated immune response is caused by varicella-zoster-specific activation of both CD4+ T-helper and CD8+ T-lymphocyte cells. The protection duration is still unknown; however, some efficacy trials have shown that the vaccine can offer continued protection for up to 10 years after vaccination. 

Administration

The varicella vaccine is only available to be administered subcutaneously. Practitioners should inject the vaccine in the upper arm's outer aspect, deltoid region, or anterolateral thigh. For adult immunization, the vaccine is administered subcutaneously as 0.5 mL in 2 doses 4 to 8 weeks apart.

Pediatric Immunization

• From 12 months to 12 years: 0.5 mL subcutaneously for 1 dose between 12 to 15 months, then 0.5 mL subcutaneously between the ages of 4 and 6.
• If ages 7 to 12 at series start, the second dose may be administered as soon as 4 weeks after the initial dose.
• If ages 13 and older at the series start, the vaccine is administered 0.5 mL subcutaneously for 2 doses 4 to 8 weeks apart.

Adverse Effects

The Varicella vaccine is safe and well-tolerated. According to some sources, injection site complaints after vaccination were slightly higher after the second dose than the first. The most commonly reported adverse effect is soreness or swelling at the injection site. Some other mild reported reactions include fever and mild vaccine-associated varicelliform rash. The rash comprises 6 to 10 papular, vesicular, erythematous lesions that peak 8 to 21 days after injection. It is rare, but other household members are susceptible to transmission when an individual has this rash after getting the vaccine. Some of the moderate reported reactions include a fever that causes a low-grade seizure (showing jerking or staring), but this is rare and more frequently reported with the MMRV vaccine 5 to 12 days after the vaccine, and upper respiratory infection, which can include a cough, chest pain, and difficulty breathing. Serious reported reactions include pneumonia, low blood cell count, and severe brain reactions. These are all extremely rare, and researchers still do not understand if the vaccine causes these reactions. After the vaccine is administered, it is recommended that salicylates be avoided for 5 weeks due to the risk of Reyes syndrome and that contact with susceptible high-risk individuals be avoided.

Contraindications

The varicella vaccine is contraindicated in individuals who have a severe allergy or have had an anaphylactic reaction to neomycin or gelatin, which are components of this vaccine, or to the previous dose of a varicella-containing vaccine.[12][13] It is also contraindicated in individuals who are immunosuppressed or immunodeficient in any of the following ways:

• Severe combined immunodeficiency, lymphoma, leukemia, AIDS, blood dyscrasias, hypogammaglobulinemia, agammaglobulinemia, IgA deficiency, malignant neoplasms affecting the bone marrow or lymphatic system, patients receiving steroids, chemotherapy, or X-rays as a treatment for cancer or X-rays
• Any patient showing clinical signs of infection with HIV
• Any person who has a family history of congenital or hereditary immunodeficiency in first-degree relatives unless there is demonstrable immunocompetence of the potential vaccine recipient

Patients can not receive the vaccine if they present with febrile illness or have active, untreated tuberculosis. Vaccination is contraindicated in pregnant females, and women should delay pregnancy for 3 months after vaccination by using effective birth control. Maternal varicella infection has been shown to harm the fetus, but the vaccination effects have not been tested on pregnant women, and the effects on fetal development are currently unknown. It is also not known whether the varicella vaccine virus passes in breast milk, and it is best to avoid vaccination during breastfeeding for that reason. There is currently no clinical data available on the efficacy or the safety of administration of the varicella vaccine in children younger than 12 months old.

Monitoring

No routine tests are recommended in conjunction with this vaccine.

Enhancing Healthcare Team Outcomes

All interprofessional healthcare team members, including clinicians (MDs, DOs, NPs, PAs), nurses, and pharmacists, are frontline professionals in preventing chickenpox. Because of the anti-vaccination sentiment in society, healthcare professionals must educate the public on the importance of vaccination.[11] For children who develop an infection, the parents should receive education on trimming the child's fingernails to minimize excoriation marks and bacterial superinfections. The pharmacist should warn the parents not to administer aspirin to young children with fever because of the risk of Reye syndrome. All pregnant women who develop chickenpox should obtain a referral to an infectious disease specialist regarding treatment. Further, postpartum women with chickenpox should be encouraged to breastfeed if they desire because it is safe.[14][15]

Outcomes

Chickenpox in a healthy individual is a self-limiting illness with an excellent outcome. However, in immunocompromised individuals, the infection can be associated with very high morbidity and mortality. The currently available Varicella vaccine is safe and well-tolerated. According to some sources, injection site complaints after vaccination were slightly higher after the second dose than the first. The most commonly reported adverse effect is soreness or swelling at the injection site.[16][17]

Varicella/herpes zoster vaccines require the collaboration of the entire interprofessional healthcare team. In many states, pharmacists are empowered to administer the vaccine in the pharmacy, and they must let the patient's physician know so records can be updated appropriately. Physicians, nurses, and pharmacists are all responsible for patient counseling and ensuring the patient is a viable vaccine candidate, in line with the abovementioned restrictions. Should they encounter any of these contraindications, they must communicate them to the entire healthcare team so all members are on the same page and patient records can be updated. This interprofessional approach ensures maximal effectiveness for varicella/herpes zoster vaccination strategies.