Human Papillomavirus Vaccine - Efficacy, Purposes and Indications

Human Papillomavirus, more commonly known by the acronym HPV is a virus transmitted through sexual contact, can cause genital warts and cervical cancer, anus, penis and oropharynx.

Vaccine or chastity belt
Vaccine or chastity belt

Each year, about 270,000 women worldwide die from tumors account in the cervix caused by HPV. In Brazil, it is estimated that each year there are about 15,000 new cases of cervical cancer.

In this article we will talk about the HPV vaccination, indications, efficacy and side effects. We'll also talk about the myths surrounding the HPV vaccine.

HPV subtypes

There are about 150 subtypes of human papillomavirus, or all able to induce malignant tumors or warts. Of these 150 types, 12 of them cause genital warts, and HPV-6 and HPV-11 subtypes most common, accounting for 90% of cases. 15 types of HPV cause cervical cancer, penis, anus, and oropharynx, and HPV-16 and HPV-18 subtypes the most dangerous.

In relation to cancer, over 70% of cases are caused by HPV-16 or HPV-18, which is why these two subtypes are the preferred targets of the currently available vaccines.

HPV vaccines available on the market

There are two distinct market HPV vaccines. The quadruple vaccine, called Gardasil, currently available for free in the public health system of various countries, acts against subtypes 6, 11, 16 and 18. This vaccine thus protects against the human papillomavirus subtypes that cause most cancer and more cause genital warts.

The other vaccine available in the market, but not in public service, is Cervarix, a double vaccine (bivalent) that protects against subtypes 16 and 18. This vaccine acts against HPV that cause cancer, but not about the HPV that cause warts genitals.

Who should be vaccinated against HPV

The HPV vaccine has been developed in order to reduce cases of cervical cancer in women. However, it is an important cause of penile and anal cancer, accounting for about 40% of cases, HPV vaccination can also be made in men.

Currently, it indicates the administration of quadruple vaccine against HPV for men and women between 9 and 26 years. In selected cases, when the doctor finds that the actual vaccine will bring benefit to the patient, the vaccine may also be indicated for people over 26 years.

From a public health perspective, however, mass immunization of the population is made differently. As penile cancer or anus are tumors much less common than cervical cancer, and how the HPV vaccine is much more effective if taken by people who have never been exposed to HPV, preferably children who have not started your life sexual, in many countries, including Brazil, the immunization schedule only indicates vaccination in girls between 9 and 13 years old.

This does not mean that men or women under 26 can not use the private health care system to be vaccinated if their doctors understand that vaccination is important.

Have already been previously infected with an HPV subtype does not contraindicate the completion of vaccination. If a woman is or has been infected with HPV-18, for example, the quadruple vaccination serves to prevent it against the other three subtypes of human papillomavirus.

Currently, a lack of studies confirming its safety for the fetus, the HPV vaccination is not recommended for pregnant women. On the other hand, during breastfeeding no contraindications.

As the vaccine is made with inactive virus, it can be given to people with HIV or other causes of immunosuppression.

HPV vaccination effectiveness

When taken in childhood before the onset of sexual activity, vaccination has an efficiency of almost 100% in the prevention of malignant neoplasms of the cervix caused by the subtypes 16 and 18. When administered to women older, already sexually active and therefore at greater risk of have been previously exposed to HPV, the efficiency drops to only 44%.

In men never exposed to HPV vaccine efficacy is somewhat lower than in women, but still reaches 90%.

Vaccination when done in women who are already infected with HPV-16 or HPV-18 apparently does not cause damage, but does not provide any beneficial effect on the current infection. It is important to note that the vaccine is to prevent HPV and not to treat it.

Currently, we do not know how long the vaccine confers immunity. As vaccines are relatively new in the market, most people under study does not have 8 years of vaccination. So, to know how long a person will be immune to HPV after vaccination will be even more necessary a few years of study.

Contrary to what occurs in many infectious diseases, there is still no post-vaccination serological tests for HPV, or blood tests that serve to measure the blood concentration of antibody against human papilloma virus after vaccination.

Among the major scientific studies that prove the effectiveness of the HPV vaccine, we can highlight three of them:
  • The FUTURE II trial - A study published in the New England Journal of Medicine, with 12,000 women aged 15 to 26, double-blind, randomized, multicenter, placebo - controlled study. The quadrivalent vaccine was 98% effective in preventing cases of CIN 2, CIN 3, adenocarcinoma in situ , or cancer of the cervix.
  • The FUTURE 1 trial - also published in the New England Journal of Medicine. Study of 5,455 women aged 16 to 24, double-blind, randomized, multicenter, placebo - controlled study. The quadrivalent vaccine was 100% effective in preventing anogenital warts, vulvar and vaginal cancers, CIN1, CIN2, CIN3 and adenocarcinoma in situ.
  • PATRICIA (Papilloma Trial against cancer in young adults) - Published in the Lancet. Study of 18,000 women between 15 and 25 years, double-blind, randomized, multicenter, placebo - controlled study. The bivalent vaccine showed efficacy of 93% in preventing cases of CIN 2, CIN 3, adenocarcinoma in situ or cervical cancer.

HPV vaccine doses

The quadruple vaccine is typically administered in 3 doses. The patient takes the first vaccine today and receiving two ribs after 2 and 6 months (call doses at 0, 2 and 6 months). In Brazil and some other countries that have adopted the quadruple vaccine in the official calendar the scheme has been done a little differently. The second dose has been recommended at 6 months interval and the third only after 5 years (time 0, 6 months and 5 years).

The bivalent vaccine is also usually administered in 3 doses at 0, 1 and 6 months.

Pap in women vaccinated

Have been vaccinated against HPV considerably reduces the risk of cervical cancer, but not away at 100%. First because the vaccine only covers the two most dangerous subtypes of HPV; second because some women may already be infected with some HPV type at the time of vaccination, with no effect of the vaccine on this infection already in progress; and third because there are cases unusual, it is true, of cervical cancer not caused by HPV.

Therefore, in no way exempts vaccination woman to do your routine Pap test.

Side effects of HPV vaccine

Despite some rumors now and then circulate among the population, the HPV vaccine is quite safe. Profile of serious side effects is similar to other vaccines present in the immunization schedule.

Unfortunately, every time there is a new vaccine, spread on the Internet and social networks obscurantist campaigns on the risks of vaccination, they only serve to alarm the population and boycotting vaccination campaigns.

Always remember that just like any vaccine, the HPV vaccine can cause mild side effects such as pain at the injection site, headache, dizziness and nausea. As the vaccine will be administered to millions of people, it is natural that in the coming months and years are reported several cases of mild side effects. This, however, does not mean that the vaccine is dangerous and should not be taken. Several other vaccines present in the vaccine schedule for decades also have frequent mild side effects.

Just as an example, an American study conducted by the CDC (Centers for Disease Control and Prevention) showed that between 2006 and 2013 were administered over 57 million doses of the quadrivalent vaccine. The number of cases reported adverse events was approximately 21 thousand, or 0.03% of vaccinations. Of these 21,000, 19 000 were mild side effects such as pain at the injection site. In the remaining 2,000 cases considered moderate to severe (0.003%), the majority were nausea, vomiting, malaise, headache, dizziness, hypotension, fever, fainting and generalized weakness.

By 2011, 34 deaths had been reported after administration of the vaccine. However, in none of them was able to establish a direct relationship with the patient indeed have been vaccinated recently.

There is also no evidence that the HPV vaccine increases the risk of the occurrence of Guillain-Barre syndrome. A study also conducted by the CDC between 2006 and 2012 showed that after 1.4 million doses of Gardasil HPV vaccine, the rate of new cases of Guillain-Barre syndrome in vaccinated women was similar to Guillain-Barre rate in the unvaccinated population.

Two side effects, however, seem to be more common in HPV vaccine than other vaccines syncope (fainting) and venous thrombosis. Still, of the 31 reported cases of venous thrombosis of the lower limbs, 29 occurred in patients with risk factors for thrombosis, such as use of hormonal contraceptives or history of clotting disorders. So there is no data to say that the vaccine has had some relation to the cases of thrombosis.

The low but real risk of fainting, it is suggested that the patient be 15 minutes rest after vaccination. It is important to note that fainting after vaccination is a relatively common event for all types of vaccine, especially in young patients who are afraid of needles.

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