Chickenpox (Varicella) Vaccine Safety

Overview

Chickenpox can be serious, especially in babies, adolescents, adults, pregnant women, and people with a weakened immune system. Some people who get chickenpox get a painful rash called shingles later in life.

Available vaccines & manufacturer package inserts

There are two chickenpox vaccines approved for use in the United States: one single antigen vaccine and one combination vaccine.

Both vaccines contain live attenuated (weakened) varicella-zoster virus. Learn more about live, attenuated vaccines.

Varivax

This shot contains only varicella vaccine.

• Single antigen varicella vaccine.
• The Food and Drug Administration (FDA) approved this vaccine in 1995 for use in people 1 year of age and older.
• There is one formula for Varivax.

ProQuad

This shot contains varicella vaccine plus other vaccines, combined into a single dose.

• Combination vaccine with varicella.
• FDA approved this vaccine in 2005 for use in children ages 1 through 12 years of age. It protects against measles, mumps, rubella, and varicella (MMRV).

There are two formulas for ProQuad:

1. ProQuad (Frozen Formulation – Recombinant Human Albumin [RHA]).
2. ProQuad (Frozen Formulation – Human Serum Albumin [HSA]).

Who should & should not get the vaccine

CDC recommends two doses of chickenpox vaccine for children, adolescents, and adults who have never had chickenpox and were never vaccinated.

Common side effects

• Sore arm from the shot.
• Fever.
• Mild rash where shot is given.
• Temporary pain and stiffness in the joints.

Vaccines, like any medicine, can have side effects. The most common side effects are usually mild and go away on their own.

Serious side effects

Serious side effects after the chickenpox vaccine are rare. The few that have been reported after vaccination include:

• Severe rash.
• Infections of the lungs or liver.
• Meningitis.
• Seizures that are often associated with fever (febrile seizures).
• General severe infection with the virus strain from the vaccine.

Some children who had these serious side effects after vaccination had weakened immune systems before they were vaccinated, but the condition had not been diagnosed before the child was vaccinated.

A closer look at the safety data

Chickenpox vaccine has been shown to be safe and well tolerated. The findings from many vaccine safety monitoring systems and years of studies have shown that chickenpox vaccines have a favorable safety profile—the body of scientific evidence overwhelmingly supports their safety.

• Before FDA licensed the vaccine, studies were done to determine the safety of 2 doses of the vaccine. In children 12 months through 12 years old:
  • 1 of 5 children had side effects, such as soreness, swelling, and redness, within 3 days of getting the first dose, compared with 1 of 4 children after the second dose.
  • 7 of 100 children had fever after the first dose, compared with 4 of 100 children after the second dose.
  • 3 of 100 children had chickenpox-like rash after the first dose, compared with 1 of 100 children after the second dose.
• In August 2019, Merck published a 22-year review of the varicella vaccine. The review included data collected from study reports submitted from March 17, 1995, through March 16, 2017, during which over 212 million doses were distributed globally. Researchers found a decrease of reported adverse events over time (around 500 per one million doses in 1995 and around 40 per one million doses in 2016) and serious adverse events comprised 0.8 reports per one million doses. The profiles of serious and non-serious adverse events were consistent with previously published reports, and identified no new or unusual safety concerns.1
• An analysis of reports during 2006-2014 after second-dose chickenpox vaccination data using the Vaccine Adverse Event Reporting System (VAERS) did not identify new or unexpected safety concerns for second dose of chickenpox vaccination.2
• Although pregnant women should not get the chickenpox vaccine, some might get the vaccine by mistake. A pregnancy registry to monitor the fetal and pregnancy outcomes of women who inadvertently received chickenpox vaccine 3 months before or at any time during pregnancy found no cases of congenital chickenpox syndrome or increased risk for other birth defects.3
• In 2008, a CDC-FDA report analyzed VAERS data from May 1995 through December 2005 of patients who reported side effects after getting chickenpox vaccine. The vaccine manufacturer, Merck, distributed 50 million doses of chickenpox vaccine during this time. The vast majority of reports were non-serious and mild, such as soreness at the injection site and rash. Serious side effects linked to the vaccine were rare.4
• Since the varicella vaccine is a live virus vaccine, the virus can become dormant and reactivate, rarely causing serious side effects. Individual case reports of varicella vaccine virus reactivation leading to vaccine-associated herpes zoster ophthalmicus and encephalitis, and meningitis have been published.567
• It is rare for vaccinated people to spread varicella vaccine virus, especially if they do not have a rash. Worldwide, since 1995, only 11 healthy vaccinated people have been documented as spreading vaccine virus to 13 unvaccinated persons. All of these vaccinated people had a rash after vaccination.

How CDC monitors vaccine safety

CDC and the Food and Drug Administration (FDA) are committed to ensuring that vaccines provided to the public are safe and effective. Once vaccines are licensed or authorized for emergency use in the United States, CDC and FDA continuously monitor them through several safety systems.

Resources