The Varicella vaccine, commonly known as the chickenpox vaccine, protects against the highly contagious virus that causes an itchy, blister-like rash. This vaccination introduces a weakened form of the varicella-zoster virus, allowing the immune system to build defenses without causing a full-blown illness. Standard recommendations for when to receive this vaccine vary primarily by age and whether an individual has previously been infected or vaccinated.
The Standard Childhood Vaccination Schedule
The routine vaccination schedule for healthy children involves a two-dose series to establish lasting immunity against the varicella virus. The first dose is typically administered between 12 and 15 months of age. This timing aligns with other routine childhood immunizations and follows the period when maternal antibodies, which can interfere with vaccine effectiveness, have sufficiently declined.
The second dose is recommended later, generally between 4 and 6 years of age, often coinciding with the child’s entry into preschool or elementary school. The second dose boosts the immune response and maximizes protection, addressing the small percentage of children who may not develop full immunity after the first dose. Studies show the two-dose regimen offers significantly better protection, reducing the risk of breakthrough cases compared to a single dose.
Catch-Up Guidelines for Adolescents and Adults
Individuals who missed the routine childhood schedule or have no documentation of immunity require catch-up vaccination. Adolescents (age 13 years and older) and adults who have never had chickenpox or received the vaccine require two doses of the varicella vaccine. These doses must be spaced apart by a defined interval to allow the immune system to respond effectively.
For this older population, the recommended minimum interval between the first and second dose is at least 28 days (four to eight weeks). The second dose ensures the highest possible efficacy, which can be over 98% with the two-dose series. Catch-up vaccination is important for non-immune adults, especially those in high-risk groups, such as healthcare workers or women planning a pregnancy, as varicella can be more severe in adults.
Medical Exemptions and Contraindications
There are specific medical circumstances where the varicella vaccine is not appropriate. A contraindication is a history of a severe allergic reaction, such as anaphylaxis, to a previous dose or to a vaccine component like gelatin or the antibiotic neomycin.
Since the varicella vaccine is a live, attenuated vaccine, it is contraindicated for people with certain severe immune deficiencies, including those with some types of HIV/AIDS, leukemia, or who are undergoing chemotherapy. The vaccine is also not given to pregnant women due to a theoretical risk to the fetus, and women should avoid becoming pregnant for about one month after vaccination. Vaccination is postponed if a person has a moderate or severe acute illness, with or without a fever, until they have recovered.