The varicella vaccine, often known as Varivax, contains a live, weakened form of the varicella-zoster virus, which causes chickenpox. This preparation stimulates the immune system to produce antibodies, providing protection against the disease. Achieving maximum immunity requires a two-dose series. Two doses are highly effective, offering protection against chickenpox in approximately 98% of recipients.
The Standard Schedule for Children
The standard schedule for the varicella vaccine offers early protection to children and ensures the second dose is given before school entry. The first dose is typically administered when a child is between 12 and 15 months of age.
A second dose is necessary to maximize protection. This second dose is routinely recommended for children between 4 and 6 years of age. This timing aligns with the standard schedule for other childhood vaccines and ensures full protection before entering kindergarten or first grade.
Minimum Time Between Doses
The interval between the two doses is determined by age, as the immune response differs between young children and older individuals. The minimum time is the shortest period allowed between the first and second dose to ensure the second dose is considered immunologically valid.
For children under 13 years old, the minimum required interval between the first and second varicella vaccine dose is three months, or twelve weeks. This three-month recommendation is in place to optimize the long-term immune response in younger recipients.
For individuals aged 13 years and older who are starting or completing the two-dose series, the minimum required interval is four weeks, or 28 days, after the first dose. This minimum is sufficient for older immune systems to mount a lasting response.
Catch-Up Schedules and Addressing Delays
The series does not need to be restarted if the second dose is late. The principle of “no maximum interval” applies to the varicella vaccine, meaning that a delay, even of several years, does not invalidate the first dose. The second dose can be given at any time after the minimum interval has passed.
For an older child or adolescent who received the first dose years ago, the healthcare provider administers the second dose at the time of the catch-up visit. The primary focus for a delayed patient is ensuring the dose is given at least three months after the first dose for those under 13, or four weeks for those 13 and older. This flexibility ensures that the series can be completed whenever the patient returns to the clinic.
MMRV Combination Vaccine Considerations
Some children between 12 months and 12 years of age may receive the measles, mumps, rubella, and varicella (MMRV) combination vaccine. If two doses of a live virus vaccine are given less than 28 days apart, the first dose may interfere with the second. For this reason, the standard practice is to separate two live viral vaccines by at least four weeks if they are not given on the same day.