Human Papilloma Virus Vaccines
Introduction to HPV Vaccines
Human Papillomavirus (HPV) vaccines are prophylactic vaccines that prevent infections by certain types of human papillomavirus. HPV is a group of more than 200 related viruses, of which about 40 are spread through direct sexual contact. Some HPV types can cause cervical cancer and other cancers, including cancers of the anus, penis, vagina, vulva, and oropharynx. HPV vaccines have been developed to prevent HPV infections and HPV-related diseases.
Key Points:
- HPV vaccines are composed of virus-like particles (VLPs) that are produced by recombinant technology.
- These VLPs contain no viral DNA, so they cannot cause infection.
- HPV vaccines work by stimulating the production of antibodies that, in future encounters with HPV, bind to the virus and prevent it from infecting cells.
- The first HPV vaccine was approved by the FDA in 2006.
Types of HPV Vaccines
There are currently three HPV vaccines approved by the FDA:
1. Gardasil 9 (9-valent HPV vaccine)
- Protects against 9 HPV types: 6, 11, 16, 18, 31, 33, 45, 52, and 58
- Covers 7 oncogenic types responsible for about 90% of cervical cancers
- Also protects against types 6 and 11, which cause 90% of genital warts
- Approved for use in males and females aged 9-45 years
2. Gardasil (quadrivalent HPV vaccine)
- Protects against 4 HPV types: 6, 11, 16, and 18
- No longer distributed in the United States (as of late 2016)
3. Cervarix (bivalent HPV vaccine)
- Protects against 2 HPV types: 16 and 18
- No longer available in the United States (as of late 2016)
Currently, Gardasil 9 is the only HPV vaccine available for use in the United States. It is produced by Merck & Co., Inc.
Vaccine Efficacy
HPV vaccines have shown high efficacy in preventing HPV infections and HPV-related diseases when administered before exposure to the virus.
Efficacy Against HPV Infection:
- Nearly 100% effective in preventing infections with HPV types included in the vaccine
- Gardasil 9 prevents infection with types responsible for about 90% of cervical cancers
Efficacy Against HPV-Related Diseases:
- Cervical Cancer: Up to 90% reduction in cervical cancer incidence
- Genital Warts: Nearly 100% effective in preventing genital warts caused by HPV 6 and 11
- Other HPV-Related Cancers: Significant reductions in anal, vulvar, vaginal, and oropharyngeal cancers
Cross-Protection:
Some evidence suggests partial cross-protection against HPV types not included in the vaccines, though this protection is not as strong or consistent as protection against vaccine types.
Long-Term Efficacy:
Studies have shown that vaccine-induced immunity remains strong for at least 10 years post-vaccination, with no evidence of waning protection.
Vaccination Schedule
The Advisory Committee on Immunization Practices (ACIP) recommends the following HPV vaccination schedules:
Routine Vaccination:
- Recommended for all adolescents at age 11 or 12 years (can start at age 9)
- Two-dose series if started before 15th birthday:
- First dose: Day 0
- Second dose: 6-12 months after the first dose
- Three-dose series if started on or after 15th birthday:
- First dose: Day 0
- Second dose: 1-2 months after the first dose
- Third dose: 6 months after the first dose
Catch-Up Vaccination:
- Recommended for all persons through age 26 years who are not adequately vaccinated
- Vaccination may be given to adults aged 27-45 years based on shared clinical decision-making
Special Populations:
- Immunocompromised persons: Three-dose series regardless of age at initiation
- Pregnant women: HPV vaccination should be delayed until after pregnancy, but pregnancy testing is not required before vaccination
Side Effects and Safety
HPV vaccines have been extensively studied and have a favorable safety profile. However, like all medical interventions, they can cause side effects.
Common Side Effects:
- Pain, redness, or swelling at the injection site
- Fever
- Headache or feeling tired
- Nausea
- Muscle or joint pain
Rare Side Effects:
- Syncope (fainting): More common in adolescents, recommended to observe patients for 15 minutes after vaccination
- Severe allergic reactions (anaphylaxis): Extremely rare, estimated at 1.7 cases per million doses
Safety Monitoring:
Multiple systems are in place to monitor vaccine safety, including:
- Vaccine Adverse Event Reporting System (VAERS)
- Vaccine Safety Datalink (VSD)
- Clinical Immunization Safety Assessment (CISA) Project
Long-Term Safety:
Long-term follow-up studies have not identified any serious safety concerns from HPV vaccination. The vaccines do not contain live virus and cannot cause HPV infection or cancer.
Public Health Impact
HPV vaccination has had a significant impact on public health since its introduction.
Reduction in HPV Prevalence:
- Up to 86% reduction in vaccine-type HPV infections among females aged 14-19 years
- 71% reduction among females aged 20-24 years
- Significant reductions also observed in males
Reduction in HPV-Related Diseases:
- Cervical Precancers: Up to 40% reduction in cervical intraepithelial neoplasia grade 2 or worse (CIN2+) among screened women
- Genital Warts: Up to 67% reduction in young women and 48% in young men
- Emerging evidence of reductions in HPV-related cancers, including cervical cancer
Herd Immunity:
Evidence suggests that HPV vaccination programs provide indirect protection to unvaccinated individuals through reduced virus circulation in the population.
Global Impact:
As of 2020, over 100 countries have introduced HPV vaccination into their national immunization programs. The WHO has set a goal to eliminate cervical cancer as a public health problem, with HPV vaccination as a key strategy.
Challenges:
- Vaccine hesitancy and misinformation
- Cost and accessibility in low- and middle-income countries
- Achieving high vaccination coverage, particularly in males
Human Papilloma Virus Vaccines
- What is HPV?
A virus that can cause certain cancers and genital warts - How many types of HPV are there?
Over 200 types - Which HPV types are considered high-risk for cancer?
Types 16 and 18 are responsible for most HPV-related cancers - What cancers can HPV cause?
Cervical, anal, penile, vaginal, vulvar, and oropharyngeal cancers - At what age is the HPV vaccine typically recommended?
11-12 years old, but can be given as early as 9 years old - Can adults get the HPV vaccine?
Yes, it's approved for use up to age 45 - How many doses of the HPV vaccine are required?
2 doses for those who start before age 15, 3 doses for those who start at or after age 15 - What is the most common HPV vaccine used globally?
Gardasil 9 - How effective is the HPV vaccine in preventing cervical cancer?
Nearly 100% effective against the HPV types included in the vaccine - Can males receive the HPV vaccine?
Yes, it's recommended for both males and females - Does the HPV vaccine protect against all types of HPV?
No, it protects against the most common cancer-causing types - Can someone who is already sexually active benefit from the HPV vaccine?
Yes, they may still benefit from protection against types they haven't been exposed to - What are the most common side effects of the HPV vaccine?
Pain, redness, and swelling at the injection site - Is the HPV vaccine safe?
Yes, it has been extensively studied and deemed safe by regulatory agencies worldwide - Can the HPV vaccine cause infertility?
No, there is no evidence that the HPV vaccine affects fertility - How long does protection from the HPV vaccine last?
Studies suggest protection lasts at least 10 years, potentially longer - Can pregnant women receive the HPV vaccine?
No, it's not recommended during pregnancy - Does the HPV vaccine contain live virus?
No, it contains virus-like particles but no live virus - Can the HPV vaccine treat existing HPV infections or related diseases?
No, it's preventive and doesn't treat existing infections or diseases - What percentage of cervical cancers can be prevented by the HPV vaccine?
Up to 90% of cervical cancers - Is the HPV vaccine covered by most insurance plans?
Yes, most insurance plans cover the vaccine for recommended age groups - Can immunocompromised individuals receive the HPV vaccine?
Yes, but they may need three doses regardless of age - What is the global coverage rate for the HPV vaccine?
As of 2023, about 20% of eligible girls worldwide have received the vaccine - In which year was the first HPV vaccine approved?
2006 - How many countries have introduced the HPV vaccine into their national immunization programs?
As of 2023, over 100 countries - Can the HPV vaccine be given at the same time as other vaccines?
Yes, it can be administered concurrently with other age-appropriate vaccines - What is the storage temperature requirement for most HPV vaccines?
2°C to 8°C (35°F to 46°F) - Is there a therapeutic HPV vaccine available?
No, currently available HPV vaccines are preventive, not therapeutic - What organization first recommended the HPV vaccine for global use?
The World Health Organization (WHO) - Can the HPV vaccine cause HPV infection?
No, the vaccine doesn't contain live virus and cannot cause HPV infection
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