HPV Vaccination Flashcards
Conditions associated with HPV infection
HPV infects human epithelial cells
There are >100 subtypes with differing propensities to infect mucosal or cutaneous tissue.
There are > 40 types of HPV that infect the anogenital area and throat, the majority of which are sexually transmitted
It has been reported that high-risk HPV strains cause 5% of all cancers worldwide
Anogenital warts: typically occur within weeks or months of infection with HPV
Strains 6 and 11 account for approximately 90%
These warts do not lead to cancer but they can cause physical discomfort, anxiety and social stigma.
Cervical cancer:
Persistent infections with HPV cause cervical cancer and the association is present in virtually all cases worldwide.
Most females infected with HPV, however, do not develop cervical cancer.
The progression from cervical intraepithelial neoplasia to cervical cancer usually occurs over 15–20 years, but a compromised immune system may accelerate this.
There were 180 cases of cervical cancer registered in NZ in 2016
Other cancers:
Infection with HPV is associated with approx 75% of oropharyngeal cancers
The incidence of HPV-related oropharyngeal cancer is increasing in NZ and is 4-5 times higher in males than females (3.01 and 0.65 cases per 100,000 population, respectively)
Infection with high-risk HPV is also associated with over 90% of anal, 70% of vulval and vaginal, and 50% of penile cancers.
These cancers are relatively rare but their prevalence in NZ is increasing.
Other conditions:
Low-risk HPV can also cause benign growths in the respiratory tract which may present as hoarseness or airway compromise.
Although rare, this can be seen in newborns who acquire the virus from the birth canal.
HPV and the benefits of vaccination
- HPV infection is spread via close skin-to-skin contact which can occur during penetrative and non-penetrative sexual contact, e.g. oral sex.
- In very rare cases, HPV can be transmitted from mother to fetus perinatally.
- Approx 80% of sexually active adults will be infected by at least one strain of HPV during their lifetime, with the risk of infection increasing in proportion to the number of sexual partners.
- The natural hx of HPV infection, i.e. without vaccination, is often transient and asymptomatic, with a loss of detectable HPV occurring after 6–12 months
- However, in some individuals the repeated division of infected cells will result in the development of anogenital warts, often weeks or months after acquiring the infection.
- The reasons why some people have persistent infections with HPV are not completely understood but may involve genetics and environmental factors such as alcohol consumption and tobacco smoking.
- In 10–20% of people the infection will persist latently over years, strongly increasing their risk of developing a neoplasia, which may eventually progress to invasive cancer.
- Consistent use of condoms only reduces the rate of transmission by 30–60% as they may not cover all areas of infection
Vaccination protects against nine strains of HPV
The current HPV vaccine, Gardasil® 9, prevents infection from nine strains of HPV, including:
- Two low-risk strains (6 and 11) that cause approximately 90% of genital warts
- Seven high-risk strains (16, 18, 31, 33, 45, 52 and 58) that cause the majority of cervical cancers and many anogenital and oropharyngeal cancers
Strains 16 and 18 are associated with approx 70% of invasive cervical cancers
HPV vaccination prevents > 97% of genital intraepithelial neoplasias (throat, cervical cancer and and anal, vaginal, vulval or penile cancers) and anogenital warts among females aged 16–26 years who have tested negative for prior infection with HPV
Less data are available regarding the vaccine’s efficacy in males, but there is evidence that > 90% of external genital lesions, including warts and genital intraepithelial neoplasias, are prevented in males aged 16–26 years.
N.B. Genital intraepithelial neoplasias are rare among young males and females.
Immunity from vaccination is more effective than immunity post-exposure to the wild virus.
Other risk factors for HPV-related cancer include:
Smoking
Early start of sexual activity
Multiple sexual partners
Women who don’t participate in regular cervical screening
Diet low in fruit and vegetables
FHx of cervical cancer
Women > 40 years of age, and women who are Māori or Pacific
Long-term immune responses occur in almost all people
One month after completing the HPV vaccination schedule, 99.6% – 100% of people aged 9–26 yrs will have antibodies present against all nine strains covered by the vaccine.
It is unclear how long protection lasts as studies are ongoing
- however, it is known to persist for at least 10 years with no decrease in efficacy
Therefore booster vaccinations are not considered necessary if the full schedule has been completed.
Vaccination is also beneficial for people who are sexually active
People who are sexually active, including those who have already been infected with HPV and those who have developed HPV-related conditions, may also benefit from vaccination.
Most significantly, the vaccine will provide these people with protection against strains of HPV they have not encountered.
It may also prevent reinfection with a strain they have been previously exposed to if they cleared the infection without producing antibodies against that strain.
Many people who are infected with HPV do not develop immunity as seroconversion is poor.
There are no safety concerns associated with vaccination in people who are already infected with HPV or who have developed an HPV-related condition
How effective has HPV vaccination been in NZ?
The number of diagnoses of genital warts has significantly decreased since the introduction of the vaccine;
- 17% decline in diagnoses in primary care in all ages from 2014 to 2015.
Data collected from Auckland showed an 83% reduction in genital wart in young females in 2013 compared with 2008, before the HPV vaccination programme was introduced.
It is too early to detect any effects of HPV vaccination on cancer rates in NZ as this requires lengthy follow-up periods.
Key practice points:
Without vaccination, appr 80% of sexually active adults will be infected by at least one strain of HPV during their lifetime
To achieve more effective “herd immunity”, vaccination rates need to be 75–80%; latest figures show 67% coverage in NZ
Vaccination against HPV before the age of 14 years is associated with a stronger immune response,
- and trials have shown that a 2‑dose course is as effective as a 3‑dose course in this age group.
The reason why vaccination is recommended at age 11–12 years is to:
- maximise the recipient’s immune response
- and avoid the need for additional doses,
- rather than it being a predictor of imminent sexual activity.
The HPV vaccine is registered for use in females aged 9–45 years and in males aged 9–26 years
However, there are no concerns that the efficacy or safety in males up to the age of 45 years will differ significantly from females of the same age or younger males.
Eligibility, Funded:
Since January, 2017, all females and males HPV immunisation is free for NZ residents aged 9 to 26 yrs, and non-residents aged 9 to 18 yrs.
Immunisation is available through participating schools or from family doctors, local health centres, and some Family Planning clinics.
The school-based HPV immunisation programme aims to vaccinate children in Year 7 or 8 (aged 11–12 years)
It is recommended that practices place an active recall for pts aged 14 years to offer the vaccination to those who have not received it; this is also an opportunity to check vaccination status in general
Ensure that all young adults, i.e. those aged 26 years and under, are aware that they are eligible for subsidised HPV vaccination
People aged 27 years and older who received at least one dose of HPV vaccine before turning 27 years can complete the schedule fully subsidised
Eligibility, Not funded:
Women aged ≤ 45 years, to help prevent HPV reinfection after colposcopy treatment for cervical abnormalities.
Pts aged ≥ 27 years who have had little exposure to HPV in the past and are now likely to be exposed.
Men who have sex with men
Pts who are HIV-positive
The unsubsidised cost of three doses varies but is approximately $500 as of February 2019
Contraindications:
Yeast allergy resulting in anaphylaxis
Hx of anaphylaxis as a result of the vaccine or any of the vaccine ingredients.
Pregnancy – If the pt does not know she is pregnant, and vaccination is given inadvertently, research has shown no significant effect on the patient or their unborn baby.
The vaccine is safe to receive while breastfeeding
Dosing schedules
age group, 9 to 14 years :
2 doses at least 6 months
The min interval is 5 months between the 2 doses.
If 2 doses are given at least 5 m apart, no further doses are required, even if the second dose is given when the pt is aged ≥ 15 years.
If doses 1 and 2 are given <5 m apart, a third HPV vaccine dose is required.
NB: For all age groups, there is no maximum interval between doses.
If the schedule has been interrupted, it is not necessary to repeat prior doses, regardless of how long ago the doses were given.
Dosing schedules
age group: 15 to 26 years (inclusive)
Max of 3 doses funded at the following intervals:
- zero (initial dose)
- 2 months
- 6 months
If an HPV dose was received when aged
If a shortened schedule is required, 3 doses can be given over a 5‑m period, with a min interval of 4 wks bet any two doses.
Dosing schedules
Special circumstances:
The vaccine is safe because it contains non-replicating, non-infectious viral subunits
Pts aged 9-26 yrs (inclusive) with:
- confirmed HIV infection
- or organ or tissue transplant (including stem cells)
require 3 doses at zero, 2, and 6 months, unless an alternative schedule is advised.
Post-chemotherapy pts:
Aged 9-26 years (inclusive) require 3 doses at zero, 2, and 6 months, unless an alternative schedule is advised.
A max of 4 doses for pts aged 9 to 26 years (inclusive), ≥ 1 month after the last dose
Aged < 27 years who have had an age-appropriate primary course before chemotherapy are eligible for an additional booster dose post-chemotherapy (usually 3 m after chemotherapy if lymphocyte count is > 1.0 x 109/L)
Vaccination rates against HPV in NZ are too low
The target for HPV vaccination is 75% coverage across all DHBs, which the MOH hoped to achieve by December, 2017.
This level of coverage is considered to provide more effective “herd immunity” where those unwilling or unable to receive the vaccine are also protected.
This target was not met, with latest figures showing only 67% coverage for females born in 2003.
The lowest rate of vaccination was in European/Others (65%), with higher rates in Māori (67%), Asian (71%) and Pacific peoples (73%)
