Varicella-Zoster and HPV Vaccine Schedules
Varicella-Zoster Vaccine
Children aged 12 months through 12 years should receive two 0.5-mL doses of varicella vaccine administered subcutaneously, with the first dose at 12-15 months and the second dose at 4-6 years of age, separated by at least 3 months. 1, 2
Dosing by Age Group
Children (12 months to 12 years):
- First dose: 12-15 months of age 1, 2
- Second dose: 4-6 years of age (before kindergarten/first grade entry), though can be given earlier 1
- Minimum interval: At least 3 months between doses 1, 2
- If second dose inadvertently given 28 days to 3 months after first dose, it does not need repeating 1
Adolescents (≥13 years) and Adults:
- Two 0.5-mL doses separated by a minimum of 4 weeks (28 days) 2
- For those who previously received only one dose, a second dose is necessary 1
Vaccine Efficacy and Rationale
The two-dose strategy provides superior protection compared to single-dose vaccination:
- 98% efficacy for prevention of any varicella disease over 10 years (compared to 94% for one dose) 1
- 100% efficacy for prevention of severe disease 1
- Recipients of two doses are 3.3-fold less likely to experience breakthrough varicella compared to one-dose recipients 1
Important Clinical Considerations
Vaccine Administration:
- Can be given intramuscularly or subcutaneously 2
- Must be reconstituted and used within 30 minutes 2
- Available as monovalent (Varivax) or combination MMRV (ProQuad) 1
Drug Interactions and Precautions:
- Avoid salicylates for 6 weeks post-vaccination due to Reye syndrome risk 2
- At least 1 month should elapse between measles-containing vaccines and varicella vaccine if not given concurrently 2
- Immune globulins and blood products may interfere with vaccine response 2
- Tuberculin skin testing should be performed before vaccination, same day, or at least 4 weeks after 2
Contraindications:
- Pregnancy (contraindicated due to live attenuated virus) 2
- Immunocompromised individuals require special consideration 2
Human Papillomavirus (HPV) Vaccine
Individuals aged 9-20 years should receive one dose of 9vHPV (Gardasil-9) vaccine, representing a simplified schedule based on recent evidence showing high effectiveness with single-dose vaccination. 3
Current Dosing Recommendations
Ages 9-20 years:
- One dose of 9vHPV vaccine 3
- This updated guidance reflects evidence showing high effectiveness against HPV infection in younger populations with follow-up to 11 years 3
- Infectious disease modeling demonstrates similar short- and long-term health outcomes between one-dose and two-dose strategies 3
Ages 21 years and older:
- Two-dose schedule should be administered 3
Special Populations:
Alternative Dosing Schedule (Historical Context)
For individuals who initiated vaccination at ages 9-14 years under previous guidelines, a 2-dose schedule was recommended 4. Three doses remain recommended for those initiating the series at ages 15-26 years under older protocols 4.
Discretionary Recommendations
Ages 27 years and older:
- Discretionary recommendation for HPV vaccination 3
- May be considered on individual basis, particularly for those with new sexual partners 5
Pregnancy:
- Updated guidance now allows HPV vaccination during pregnancy 3
Public Health Impact
The simplified one-dose schedule addresses critical coverage gaps:
- Current HPV vaccine coverage falls short of the national goal of 90% coverage for two or more doses by age 17 3
- One-dose schedules can improve coverage rates compared to multi-dose programs 3
- Approximately 75% of people in Canada will acquire HPV infection in their lifetime without vaccination 3
Clinical Pearls
Catch-up Vaccination:
- Routine vaccination recommended at age 11-12 years since 2006 for females and 2011 for males 4
- Catch-up vaccination opportunities can be identified during influenza or COVID-19 vaccine appointments 6
Vaccine Hesitancy Considerations: