What is the typical dosing schedule for ProQuad (measles, mumps, rubella, and varicella vaccine)?

ProQuad Dosing Schedule

ProQuad is administered as a 2-dose series, with the first dose given at 12-15 months of age and the second dose at 4-6 years of age. 1

Standard Dosing Schedule

First Dose Timing

• Administer the first dose between 12-15 months of age as part of routine childhood immunization 1
• The minimum age for ProQuad administration is 12 months 2, 1
• ProQuad is only approved for children aged 12 months through 12 years 2, 1

Second Dose Timing

• Give the second dose routinely at 4-6 years of age (before entering prekindergarten, kindergarten, or first grade) 1
• This timing is strategically chosen because varicella incidence and outbreaks are higher among elementary school-aged children compared to preschool-aged children 1
• For children aged ≥48 months (4 years), MMRV (ProQuad) is generally preferred over separate MMR and varicella injections 3

Minimum Intervals Between Doses

Children 12 Months Through 12 Years

• The minimum interval between first and second doses is 3 months 1
• If the second dose is inadvertently administered between 28 days and 3 months after the first dose, it does not need to be repeated 1

Accelerated Schedule Option

• The second dose may be administered earlier than 4-6 years, provided the minimum 3-month interval is met 1
• This flexibility allows for catch-up vaccination when needed 1

Important Clinical Considerations

Age-Specific Febrile Seizure Risk

• For children aged 12-47 months receiving their first measles-containing vaccine dose, consider using separate MMR and varicella vaccines instead of MMRV due to increased febrile seizure risk 3, 4
• MMRV carries approximately one additional febrile seizure per 2,300-2,600 doses compared to separate vaccines in children aged 12-23 months 4
• Children aged 4-6 years who received MMRV had no increased risk for febrile seizures, making ProQuad the preferred option at this age 3

Contraindication for ProQuad

• Personal or family history (sibling or parent) of seizures is a contraindication for ProQuad; use separate MMR and varicella vaccines instead 3, 4

Storage and Administration

• ProQuad is lyophilized and must be stored frozen at an average temperature of -15°C or colder until reconstitution 2
• After reconstitution, keep at room temperature for a maximum of 30 minutes 2
• Each 0.5 mL dose contains a minimum of 3.99 log10 PFU of varicella virus, which is higher than the monovalent varicella vaccine 2

Clinical Efficacy of Two-Dose Schedule

• Two doses provide 98% vaccine efficacy compared to 94% for a single dose 1
• Recipients of 2 doses are 3.3-fold less likely to have breakthrough varicella compared to those who received only 1 dose 1
• After two doses, >99% of children achieve protective antibody levels against varicella 1