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Human Papillomavirus (HPV)

What is it?

Human papillomavirus (HPV) is a virus that can cause genital warts and cancers such as cervical cancer, anal cancer, and cancer in the back of the throat. There are more than 100 strains of HPV, but not all of them cause cancer. 


Protection against HPV is important:

  • HPV is very common: approximately 80% of people who are sexually active will contract HPV in their lifetime. 

  • Before the HPV vaccine, cervical cancer was the most common cause of cancer death in the US among women.

  • Since the vaccine, HPV infections from the types that cause the most cancer and genital warts have dropped 88% among young women. 

This vaccine offers the best protection if it is given before any exposure to HPV.

The HPV vaccine, Gardasil 9, is listed on the immunization schedule for 11-12 year olds, but children can receive this vaccine as early as 9 years old. Getting vaccinated earlier is generally recommended in order to decrease the likelihood of prior exposure to HPV. 

Children need two doses of this vaccine 6-12 months apart if they get vaccinated before they are 15. If they do not get vaccinated against HPV until they are 15 or older, they need to receive 3 doses. 

For more information about HPV vaccination, click here.

Gardasil Ingredients:

Active ingredient:

Gardasil 9 uses proteins (not whole virus) from 9 strains of HPV as antigens. You cannot get HPV from the vaccine. 


These proteins allow the immune system to make antibodies that teach your body how to respond if it is exposed to the virus in the future

  • HPV Type 6 L1 protein 

  • HPV Type 11 L1 protein

  • HPV Type 16 L1 protein

  • HPV Type 18 L1 protein

  • HPV Type 31 L1 protein

  • HPV Type 33 L1 protein

  • HPV Type 45 L1 protein

About Gardasil 9

Gardasil 9 is a recombinant protein vaccine: the information for how to make specific proteins is inserted into the genome of Saccharomyces cerevisiae (yeast).

The yeast produce the proteins, which are used as the active ingredients in the vaccine. The proteins act as antigens that allow the immune system to make antibodies against HPV. Because these are proteins, not whole bacteria, you cannot get HPV from the vaccine.

Note: This vaccine contains a small amount of yeast because it is used in the manufacturing process, but even people with yeast allergies can safely receive this vaccine. If you have concerns about a yeast allergy (or an allergy to any other ingredient), please contact your doctor.

Inactive ingredients:
Amounts are based on a 0.5 mL dose

Salts: help maintain the stability and pH of the vaccine

Adjuvants: strengthen the immune response to the vaccine


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Relevant Terms

  • Adjuvant: a compound added to some vaccines to strengthen the immune response

  • Antibody: a protein made by the immune system in response to a foreign particle (antigen). These proteins circulate in the blood and help defend the body against the substance.  

  • Antigen: This is any substance that triggers the immune system to create antibodies. For example, allergens such as pollen are antigens.

  • Emulsifier: a substance that helps to keep the ingredients mixed together

  • pH: a measure of how acidic or basic a solution is. The scale ranges from 0 (very acidic) to 14 (very basic). A pH of 7 is neutral.


Last updated: Feb. 12, 2023

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