What are the recommended dosing schedules, routes of administration, and contraindications for the live‑attenuated varicella vaccine (Varivax), the recombinant zoster vaccine (Shingrix), and the 9‑valent human papillomavirus vaccine (Gardasil‑9)?

Vaccine Dosing, Administration, and Contraindications

Varicella Vaccine (Varivax)

Dosing Schedule

Children aged 12 months through 12 years should receive two 0.5-mL doses of varicella vaccine administered subcutaneously, with a minimum interval of 3 months between doses. 1 The first dose is routinely given at 12–15 months of age, and the second dose is recommended at 4–6 years (before entering kindergarten or first grade), though it may be administered earlier if at least 3 months have elapsed since the first dose. 1

• If the second dose is inadvertently administered between 28 days and 3 months after the first dose, it is considered valid and does not need to be repeated. 1
• Persons aged ≥13 years without evidence of immunity should receive two 0.5-mL doses separated by a minimum of 4–8 weeks. 1
• If more than 8 weeks elapse after the first dose, the second dose may be administered without restarting the schedule. 1

Route of Administration

• Varivax is administered subcutaneously. 1, 2
• The vaccine is sensitive to heat and requires proper storage. 2

Contraindications

• Pregnancy: Women should be assessed for varicella immunity during pregnancy; those without evidence of immunity should receive the first dose upon completion or termination of pregnancy and before discharge from the healthcare facility, with the second dose 4–8 weeks later. 1
• Immunocompromised persons: Varicella vaccine is a live-attenuated vaccine and is generally contraindicated in severely immunocompromised individuals. 1
• Persons with severe allergic reactions to vaccine components should not receive the vaccine. 1

Important Timing Considerations

When varicella vaccine and MMR are not given on the same day, they must be separated by at least 28 days to avoid viral interference. 3 If administered less than 28 days apart, the dose given too early is invalid and must be repeated at least 28 days after the prior valid dose. 3

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Recombinant Zoster Vaccine (Shingrix/RZV)

Dosing Schedule

Adults aged ≥50 years should receive two 0.5-mL doses of recombinant zoster vaccine administered intramuscularly, with the second dose given 2–6 months after the first dose. 4 The vaccine was initially recommended for adults aged ≥60 years 1, but current recommendations extend to adults aged ≥50 years and immunocompromised adults aged ≥19 years. 4

• For immunocompromised adults aged ≥19 years who are or will be at increased risk due to disease or therapy, two doses of RZV are recommended. 4
• A single dose of the older live zoster vaccine (ZVL/Zostavax) was previously recommended for adults aged ≥60 years, but RZV is now preferred due to superior efficacy. 5, 6

Route of Administration

• RZV is administered intramuscularly, typically in the deltoid region. 4

Contraindications

• Pregnancy: RZV should be delayed until after pregnancy if indicated, as it has not been studied in pregnant women. 1
• Severe allergic reaction to any component of the vaccine or after a previous dose is a contraindication. 4
• RZV is NOT contraindicated in immunocompromised persons because it is a non-live, recombinant subunit vaccine. 5, 6, 4

Efficacy and Safety

• Two-dose RZV effectiveness is 76% overall and 79% in the first year, with minimal waning (73% at 3–4 years). 7 This is lower than the 97% efficacy seen in clinical trials but remains highly protective. 6, 7
• One-dose effectiveness wanes substantially after 1 year (from 70% to 45–52%), underscoring the critical importance of completing the two-dose series. 7
• RZV is more reactogenic than placebo, with injection-site reactions, myalgia, and fatigue being the most common adverse events, though most are transient and mild to moderate. 6, 8

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9-Valent HPV Vaccine (Gardasil-9)

Dosing Schedule

The dosing schedule depends on the age at which the vaccine series is initiated: 9

Ages 9–14 Years

• Two-dose schedule (preferred): 0.5-mL doses given at 0 and 6–12 months. 9
• If the second dose is given earlier than 5 months after the first, a third dose must be administered at least 4 months after the second dose. 9
• A three-dose schedule (0,2,6 months) may also be used at the discretion of the healthcare provider. 9

Ages 15–26 Years

• Three-dose schedule (required): 0.5-mL doses given at 0,2, and 6 months. 9

Catch-Up and Special Populations

• HPV vaccination is recommended for all individuals aged 9–26 years who have not completed the series. 1
• History of genital warts, abnormal Pap test, or positive HPV DNA test is not evidence of prior infection with all vaccine HPV types; vaccination is still recommended. 1
• For males aged 22–26 years, vaccination may be given; it is specifically recommended for men who have sex with men and immunocompromised persons through age 26 years. 1

Route of Administration

• Gardasil-9 is administered intramuscularly, typically in the deltoid region of the upper arm or the anterolateral thigh. 9
• The vaccine should be shaken well before use to maintain suspension. 9
• Observe patients for 15 minutes after administration due to risk of syncope, which may result in falls and injury. 9

Contraindications

• Pregnancy: HPV vaccination is not recommended during pregnancy; if pregnancy is discovered after initiating the series, delay the remaining doses until after pregnancy. 1, 9
• Severe allergic reaction to yeast, a previous dose of Gardasil-9 or Gardasil, or any vaccine component (amorphous aluminum hydroxyphosphate sulfate, polysorbate 80) is a contraindication. 9
• HPV vaccine is NOT a live vaccine and can be administered to immunocompromised persons, though immune response may be reduced. 1

Co-Administration

• Gardasil-9 can be given simultaneously with Menactra (meningococcal vaccine) and Adacel (Tdap), though more injection-site swelling may occur. 9

Important Limitations

• Gardasil-9 does not eliminate the need for cervical cancer screening; women must continue routine screening per standard of care. 9
• The vaccine does not protect against HPV types to which a person has already been exposed or against diseases caused by HPV types other than 6,11,16,18,31,33,45,52, and 58. 9
• Gardasil-9 is not a treatment for existing HPV-related lesions or cancers. 9

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Common Pitfalls and Practical Considerations

Timing Errors with Live Vaccines

• A critical pitfall is administering varicella and MMR vaccines less than 28 days apart when not given simultaneously. 3 This invalidates the second vaccine and requires revaccination. 3
• To avoid timing errors, strongly consider administering varicella and MMR simultaneously at the same visit whenever both are indicated. 3

Importance of Completing Series

• For RZV, one-dose effectiveness drops significantly after the first year, making the second dose essential for durable protection. 7
• For Gardasil-9 in adolescents aged 9–14 years, if the second dose is given before 5 months, a third dose is mandatory. 9

Special Populations

• Healthcare personnel and pregnant women born before 1980 should NOT be considered immune to varicella based on birth year alone; they require documentation of immunity or vaccination. 1
• Immunocompromised adults can safely receive RZV and Gardasil-9 (both non-live vaccines) but should NOT receive live varicella vaccine. 5, 6, 4