The Varicella Vaccine: What's In A Name?

The varicella vaccine, also known as the chickenpox vaccine, is an immunization to protect children and adults from the varicella-zoster virus, which causes chickenpox. The varicella-zoster virus, commonly known as chickenpox, causes an itchy rash with fluid-filled blisters. In many cases, chickenpox is mild, but sometimes it can be severe and even life-threatening. The risk of chickenpox is highest in infants, older adults, and immunocompromised people. The varicella vaccine is given by injection just under the skin and is indicated for active immunization for the prevention of varicella in individuals 12 months of age or older. The two licensed vaccines containing the varicella virus that are available in the United States are Varivax® and ProQuad®.

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Varicella vaccine effectiveness

The varicella vaccine is marketed under the name Varivax® (single-antigen varicella vaccine) and ProQuad® (combination measles, mumps, rubella, and varicella (MMRV) vaccine). Both vaccines contain live, attenuated varicella-zoster viruses derived from the Oka strain.

Varivax® is indicated for active immunization for the prevention of varicella in individuals 12 months of age or older. The first dose is administered between 12 and 15 months of age, and the second dose is administered between 4 to 6 years of age. For adolescents and adults, two doses are administered with a minimum interval of 4 weeks between doses.

ProQuad® is approved for healthy children in a similar age group, with the first dose recommended for children 12 through 47 months old. For individuals aged 15 months to 12 years, the MMRV vaccine is generally preferred for the second dose of measles, mumps, rubella, and varicella vaccines.

The effectiveness of the varicella vaccine has been evaluated in various studies. A case-control study conducted from 1997 to 2003 showed that one dose of the vaccine was 97% effective in the first year after vaccination, 86% effective in the second year, and maintained an effectiveness of 81 to 86% from the second to eighth year. A meta-analysis reported through 2015 found an effectiveness of 82% within the first decade for one-dose vaccine effectiveness.

However, the effectiveness of the vaccine declines over time since the first dose. A case-control study in Navarre, Spain, from 2010 to 2012, found that the effectiveness of one dose was 87%, while two doses had an effectiveness of 97%. The study also showed that the effectiveness of one dose declined to 61% after the third year.

Clinical trials and other studies have demonstrated that two doses of the varicella vaccine provide improved protection. A clinical trial showed that children with two doses were protected even 10 years after vaccination, and the risk of breakthrough varicella was lower compared to those with one dose. Another study reported a pooled estimate of 92% effectiveness assessed approximately five years after vaccination with two doses.

Varivax® vaccine

Varivax® is a vaccine for the prevention of varicella, also known as chickenpox. It is indicated for active immunization in individuals aged 12 months or older. The vaccine is administered in two doses of approximately 0.5 mL each, given either intramuscularly or subcutaneously. The second dose should be administered after a minimum interval of 3-4 months.

Varivax® contains a live, attenuated varicella-zoster virus derived from the Oka strain. While it is effective in preventing varicella, it may not protect all healthy individuals. Clinical trials have shown that children who received two doses of Varivax® were protected for at least 10 years after vaccination, with a lower risk of breakthrough varicella compared to those who received only one dose. However, the long-term effects of the vaccine on the incidence of herpes zoster are unknown, especially in individuals exposed to wild-type varicella.

It is important to note that Varivax® is contraindicated for individuals with a history of severe allergic reactions to any component of the vaccine, including neomycin and gelatin. It should also not be administered to pregnant women or those planning to become pregnant in the next 3 months, as the wild-type varicella virus can cause congenital varicella. Additionally, vaccine recipients should avoid close contact with high-risk individuals susceptible to varicella due to the possible risk of transmission.

Varivax® is one of the two vaccines containing the varicella virus that are licensed for use in the United States. The other vaccine is ProQuad®, which is a combination measles, mumps, rubella, and varicella (MMRV) vaccine. Both vaccines are approved for routine 2-dose varicella vaccination in healthy children.

ProQuad® vaccine

ProQuad® is a vaccine that helps protect against measles, mumps, rubella, and varicella (chickenpox). It is given to children from 12 months of age to help protect them against these diseases. However, in certain situations, it can be given to children as young as 9 months old, such as during a national vaccination programme, an outbreak, or when travelling to a region with a high prevalence of measles.

ProQuad® contains weakened forms of the viruses that cause measles, mumps, rubella, and chickenpox. When a person receives the vaccine, it triggers an immune response against these weakened viruses. Later, when the person comes into contact with the actual viruses, their immune system recognises them and is prepared to fight them off, protecting the person from the disease.

The vaccine is injected into a muscle or under the skin, preferably in the thigh for younger children and in the upper arm for older children and adults. For children above 12 months of age, one ProQuad® injection is sufficient for protection against measles, mumps, and rubella. However, to protect against chickenpox, a second injection is needed 1 to 3 months after the first one.

While ProQuad® is generally safe, there are some precautions and contraindications to be aware of. It is associated with a higher relative risk of febrile seizures, especially 5 to 12 days after vaccination, compared to separate injections of measles, mumps, and rubella vaccines. Individuals with a personal or family history of seizures or hypersensitivity to any component of the vaccine should use caution. Additionally, ProQuad® is contraindicated in pregnant women and those planning to become pregnant in the next 3 months.

ProQuad® has been authorised for use in the EU and is recommended by doctors as an effective way to protect against measles, mumps, rubella, and varicella (chickenpox). It is an important tool in preventing outbreaks and reducing the spread of these diseases, especially in school settings where children are in close contact with each other.

Chickenpox vaccine side effects

Chickenpox, also known as varicella, is a highly contagious disease caused by the varicella-zoster virus (VZV). The chickenpox vaccine is recommended for children over 12 months old and people who live with someone with a weakened immune system. The two vaccines containing the varicella virus that are licensed for use in the United States are Varivax® and ProQuad®. Varivax® is a single-antigen varicella vaccine, while ProQuad® is a combination measles, mumps, rubella, and varicella (MMRV) vaccine.

Like any medicine, vaccines can have side effects. However, serious side effects from the chickenpox vaccine are rare. In a 2008 CDC-FDA report, the vast majority of side effects reported after the chickenpox vaccine were mild and non-serious, such as soreness at the injection site and rashes. Here are some common side effects that may occur after receiving the chickenpox vaccine:

• Mild chickenpox-like rash, usually at the injection site but occasionally elsewhere on the body
• Localised pain, redness, and swelling at the injection site
• Injection-site lump that may last several weeks
• Fever (can be above 39˚C) in the 5 to 12 days after immunisation
• Temporary pain and stiffness in the joints

Serious side effects that have been reported, although rare, include:

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

It is important to note that some individuals with weakened immune systems or certain medical conditions may be advised against receiving the chickenpox vaccine. Pregnant women, for example, should not receive the vaccine as it contains a live, attenuated varicella virus. Additionally, individuals with a history of severe allergic reactions to any component of the vaccine or those with specific medical conditions like untreated tuberculosis should avoid the vaccine.

Chickenpox vaccine recommendations

Chickenpox, or the varicella infection, is a highly contagious disease caused by the varicella-zoster virus (VZV). The infection causes fever and an itchy rash, with blister-like lesions usually on the face, scalp, and trunk. It is spread from an infected person who sneezes, coughs, or shares food or drink, even before symptoms show. Adolescents and adults who contract chickenpox are at a higher risk of severe symptoms than young children.

The chickenpox vaccine is a highly effective way to protect against chickenpox. Two vaccines containing the varicella virus are licensed for use in the United States: Varivax® and ProQuad®. Varivax® is a single-antigen varicella vaccine, while ProQuad® is a combination measles, mumps, rubella, and varicella (MMRV) vaccine. Both vaccines contain live, attenuated varicella-zoster viruses derived from the Oka strain. The CDC recommends two doses of either vaccine for children, adolescents, and adults who do not have evidence of immunity.

For children, the first dose is typically administered between 12 and 15 months of age, and the second dose is given between 4 to 6 years of age. There should be a minimum interval of 3 to 4 months between the two doses. Children under 13 years old should receive two doses, and the MMRV vaccine is only approved for use in children up to 12 years old.

For adolescents and adults 13 years and older, two doses are also recommended, with a minimum interval of 4 weeks between doses. Individuals in this age group without evidence of immunity should receive two doses 4 to 8 weeks apart.

It is important to note that the duration of protection from the varicella infection after vaccination with Varivax® is unknown. Vaccination may not guarantee protection for all healthy individuals, and it is contraindicated for use in pregnant women due to the risk of congenital varicella. Additionally, individuals with a history of severe allergic reactions or immunodeficiency should not receive the vaccine.

The chickenpox vaccine is an effective way to control outbreaks and protect individuals from severe symptoms. It is recommended that all children entering childcare or starting school be up to date on their chickenpox vaccine to prevent outbreaks and reduce illness-related absences.

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