Varicella (Chickenpox) Vaccine

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Continuing Education Activity

Varicella-zoster virus (chickenpox) is an acute febrile rash illness that was very common in children in the United States before the universal vaccination program came into existence. Luckily, the varicella-zoster virus is a vaccine-preventable disease. The FDA approves the use of the live varicella virus vaccine to provide immunity for preventing varicella in individuals 12 months older. This activity reviews the mechanism of action, indications, contraindications, adverse effects of this vaccine, and the front-line personnel involved in the prevention of the disease.


  • Identify the goals of vaccination with the varicella vaccine.

  • Describe the mechanism of action of the varicella vaccine.

  • Describe the potential adverse reactions expected following vaccination with the varicella vaccine.

  • Explain interprofessional team strategies for improving care coordination and communication to advance varicella vaccination and improve patient outcomes.


Varicella or chickenpox is a common and highly contagious exanthematic disease caused by the varicella-zoster virus (VZV) that during primary infection can establish latency. VZV reactivation, even decades after primary infection, causes herpes zoster. Varicella still represents the most widespread vaccine-preventable childhood infectious disease in industrialized countries; due to its relevant burden on healthcare resources, several countries have introduced varicella vaccination into the recommended routine childhood national immunization schedule.[1] 

Varicella-zoster virus (chickenpox)  was very common in children in the United States before the universal vaccination program came into existence.[2] The varicella-zoster virus manifestations are usually very mild and self-limited, but in young infants and adults, the complications can be life-threatening. Luckily, the varicella-zoster virus is a vaccine-preventable disease, and the FDA approves the use of the live varicella virus vaccine to provide immunity for the prevention of varicella in individuals 12 months and older. Current vaccines against varicella and herpes zoster are not 100% efficacious; it is between 70% and 90% effective at preventing varicella and over 95% effective at preventing severe varicella.[3] Specifically, studies have shown that one dose of varicella vaccine can lead to breakthrough varicella, albeit rarely, in children, and a 2-dose regimen is now recommended.[4] The varicella vaccine is used routinely in children with two doses.

The first dose is given to children between 12 to 15 months of age, and the administration of the second dose is for children between 4 to 6 years old.[5][6] If three months have passed since the first dose, one may opt to give the second dose earlier. If a child has never been vaccinated or had chickenpox, the practitioner should give the two doses at least 28 days apart. One may give the varicella vaccine at the same time as other vaccines; however, evidence demonstrates an increase in the breakthrough disease when the varicella vaccine administration is within four weeks of the measles-mumps-rubella (MMR) vaccine. The recommendation is to give the vaccines simultaneously in different injection sites or to give them four weeks apart. A quadrivalent combination vaccine also exists called MMRV, which consists of MMR and varicella and may be provided in place of the two individual doses if the child is younger than 12 years old. The FDA has not approved the use of this vaccine in pregnancy and requires intense immune status evaluation in individuals with a family history of congenital immunodeficiencies.[7][8] 

The varicella vaccine is now FDA approved to give for post-exposure use and outbreak control. The vaccine should be given as soon as possible after exposure, but it has shown effectiveness in preventing or modifying disease when given within three to five days post-exposure.[9] Oral acyclovir administered during the virus's incubation period may also modify varicella disease in a healthy child. However, this practice has not yet been FDA approved and needs further evaluation. There also exists a high-titer anti-varicella virus immune globulin, which can be used as prophylaxis in immunocompromised children, pregnant women, and newborns exposed to varicella. Another indication for prophylaxis with the immune globulin is in close contact with a high-risk susceptible individual and someone who has herpes zoster.[10][11]

You can demonstrate evidence of immunity to varicella by showing documentation. The following documentation will prove age-appropriate vaccination with varicella vaccine:

  • Preschool-age children (older than 12 months): one dose
  • School-age children, adolescents, and adults: two doses
  • Laboratory evidence or confirmation of the disease
  • Birth in the United States before 1980; unless one is immunocompromised, a pregnant woman, or a health care worker (born before 1980 does not count as evidence of immunity in this population)
  • Diagnosis or verification of a history of varicella disease by a healthcare provider
  • Diagnosis or verification of a history of herpes zoster by a healthcare provider

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 by varicella-zoster-specific activation of both CD4+ T-helper and CD8+ T-lymphocyte cells. The duration of protection is currently still unknown; however, there is evidence shown in some efficacy trials that the vaccine can offer continued protection for up to ten years after vaccination. 


The varicella vaccine is only available to be administered subcutaneously. It is best when practitioners inject the vaccine in the outer aspect of the upper arm in the deltoid region or anterolateral thigh.

For adult immunization, the varicella vaccine is administered as 0.5 mL subcutaneously for two doses 4 to 8 weeks apart.

Pediatric Immunization

  • From 12 months to 12 years: 0.5 mL subcutaneously for one 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

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 six to ten papular, vesicular, erythematous lesions, which peak around eight to 21 days after injection. It is rare, but when an individual has this rash after getting the vaccine, other household members are susceptible to transmission.

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 five 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 administration of the vaccine, it is recommended to avoid salicylates for five weeks due to the risk of Reyes syndrome and to avoid contact with susceptible high-risk individuals.


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 three months after vaccination by using effective birth control. Maternal varicella infection has been shown to harm the fetus, but the vaccination effects have not had testing 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.


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] [Level 5]


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] [Level 5]

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 all bear responsibility for patient counseling and ensuring the patient is a viable vaccine candidate, in line with the restrictions outlined above. 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. [Level 5]



Vasudha Kota


Marc J. Grella


1/30/2023 4:25:46 PM



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