What to Know About Gardasil 9

Only Vaccine Approved for Human Papillomavirus (HPV) in the US

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Gardasil-9 is a vaccine used to prevent human papillomavirus (HPV) infection. It specifically protects against nine high-risk strains of HPV associated with genital warts and certain cancers, including cervical cancer. It replaced an early version of the vaccine (Gardasil-4) in 2017, which protected against four high-risk types.

Young doctor giving a patient injection.
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Gardasil-9 s a recombinant vaccine made through genetic engineering. It uses a small piece of viral DNA to "teach" yeast cells how to produce viral surface proteins. When injected into the body, these harmless proteins stimulate the production of defensive antibodies that ward off infection.

Gardasil-9 is given by intramuscular injection (into a large muscle) in a series of two or three doses depending on a person's age.

With the discontinuation of Cervarix (an HPV vaccine that protected against high-risk types) in 2016, Gardasil-9 is today the only HPV vaccine approved for use by the U.S. Food and Drug Administration (FDA).


HPV is a group of around 200 similar viruses, more than 40 of which are sexually transmitted. Among the sexually transmitted variants, some are known to cause genital warts, while others are strongly linked to cervical cancer, anal cancer, penile cancer, vaginal cancer, vulvar cancer, and head and neck cancers.

Gardasil-9 protects against nine high-risk types of HPV, two of which cause genital warts (types 6 and 11) and seven of which are linked to cancer (types 16, 18, 31, 33, 45, 52, and 58).

According to the Centers for Disease Control and Prevention (CDC), HPV is responsible for more than 90% of cervical and cancers, 70% of vaginal and vulvar cancers, and 60% of penile cancers. HPV types 16 and 18 account for the majority of these.

ACIP Recommendations

Gardasil-9 is approved by the FDA for use in people ages 9 through 45. With that being said, the strength of the recommendations varies by age group.

In the United States, vaccination recommendations are issued by a group of experts within the CDC called the Advisory Committee on Immunization Practices (ACIP). The committee currently recommends Gardasil-9 vaccination in the following groups:

  • All girls and boys ages 11 to 12 years
  • Children as young as 9 who may be at risk of exposure to HPV
  • People 13 to 26 who have not been vaccinated or completed the vaccine series

Because the HPV types protected by Gardasil-9 are sexually transmitted, the ACIP recommends vaccination at a younger age before most children are sexually active.

Moreover, multiple studies have shown that two doses of the vaccine given to 9- to 14-year-olds provide better antibody response than three doses given to older adolescents or young adults.


Despite the FDA approval, the ACIP does not recommend vaccination in adults 27 to 45 years of age. This is because the majority of people will have already been exposed to the virus by then.

Even so, the ACIP acknowledges that circumstances vary by individual and allows for the use of Gardasil-9 in this older age group, as doing so will not cause harm even if doesn't necessarily help.

HPV is so common that nearly all women and men will get it at some point in their lives. According to the CDC, nearly 80 million people are currently infected in the United States, while an estimated 14 million are infected each year.

Even so, the majority of HPV infections will clear on their own with no long-term consequence, while only a small handful will progress to cancer.

Before Taking

There are few contraindications to the use of Gardasil-9. The only absolute contraindication is a prior hypersensitive reaction to the vaccine or a severe allergic reaction to yeast.

Symptoms of drug hypersensitivity include:

  • A rash or hives
  • Fever
  • Chills
  • Dizziness
  • Swelling
  • Shortness of breath or wheezing
  • Muscle or joint pain

If you had a reaction of the sort after receiving a dose of Gardasil-9, you should not receive another.

In addition, you need to advise your doctor if you or your child is immunocompromised. This includes anyone with HIV, as well as organ transplant recipients, children with primary immunodeficiency (PID), or anyone undergoing chemotherapy.

Being immunocompromised doesn't place an individual at any risk from the vaccine. However, it may require an additional dose to ensure a more robust immune response.


Gardasil-9 is available either in single-use vials or single-use prefilled syringes. Each dose, administered by a healthcare professional, contains 0.5 milliliters (mL) of the vaccine.

The recommended dosage varies by a person's age or immune status.

Age  Doses Timing
9 to 14 years 2 The second dose is given 6 to 12 months after the first dose (0, 6-12 month schedule).
15 to 45 years 3 The second dose is given 1 to 2 months after the first dose, and the third dose is given 6 months after the first dose (0, 1-2, 6 month schedule).
Immunocompromised children 9 to 14 years 3 Same as for 15- to 45-year-olds.

The injection is most often delivered to the deltoid muscle of the shoulder but can also be delivered to the upper and outer portion of the front of the thigh (also known as the anterolateral thigh).

Side Effects

Side effects are common with all vaccines, although with Gardasil-9 they tend to mild and resolve on their own within a day or so. On rare occasions, severe complications have been known to occur.


There are four common side effects experienced by anywhere from 11% to 90% of people who receive Gardasil-9. The incidence of these varies by age and sex.

Injection site pain 89.3% 71.5% 89.9% 63.4% 82.8%
Injection site swelling 47.8% 26.9% 40% 20.2% 23.3%
Injection site redness 34.1% 24.9% 34% 20.7% 16.9%
Headache 11.4% uncommon 14.6% uncommon 13.6%
* There were not enough men ages 27-45 in premarket studies to calculate the incidence of side effects.

Fever can also occur, albeit uncommonly; if it does, it tends to be mild (under 100° F). Diarrhea, fatigue, and stomach aches have also been reported.

Fainting (syncope) has been known to occur in some immediately after the injection. This is usually transient and will quickly pass. Even so, anyone given Gardasil-9 should be monitored for 15 minutes after receiving a dose to be safe.

If lightheadedness occurs, the person should be seated with their head placed between their legs until the feeling passes.


Severe reactions are rare with Gardasil-9. Arguably, the greatest concern is the risk of drug hypersensitivity which can affect people with no history of allergy. Even so, the chances of this occurring are slim.

Anaphylaxis, a potentially life-threatening whole-body reaction, is not commonly associated with Gardasil-9. According to the World Health Organization, anaphylaxis occurs at a rate of only 1.7 cases per million doses of the HPV vaccine.

Warnings and Interactions

Gardasil can greatly reduce the risk of genital warts and certain cancers, but that doesn't necessarily mean you won't get them. This is especially true if you are vaccinated later rather than earlier. Moreover, not all genital, anal, or oral cancers are caused by HPV.

A 2018 review in the Journal of Infectious Diseases reported that Gardasil-9 has the potential to prevent around 90% of cervical cancers and HPV-related vulvar, vaginal, and anal cancers.

As impressive as these findings are, they shouldn't suggest that you can avoid or delay recommended cancer screenings, including Pap smears, or pay any less attention to signs and symptoms of cancer.

Potential Interactions

In addition, you need to advise your doctor if you or your child are undergoing any immunosuppressive therapy prior to getting the shots. These treatments can blunt your immune response and undermine the effectiveness of Gardasil-9.

Let your doctor know if you are on:

For people on these therapies, a third Gardasil-9 dose will likely be recommended.

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Article Sources
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