HPV VACCINE | EFFICACY, EFFECTS AND INDICATIONS
The human papillomavirus, known by the acronym HPV is a virus transmitted through sexual contact, can cause genital warts and cervical cancer, anus, penis and oropharynx.
Each year, about 270,000 women worldwide die from tumors account in the cervix caused by HPV. In Brazil, it is estimated that annually there are about 15,000 new cases of cervical cancer.
In this article we will talk about the HPV vaccination, as has been implemented in the immunization schedule in many countries in recent years.
If you are looking for information about HPV or genital wart, follow the links:
Before we go on, check out this short video, produced by MD.Saúde team, explaining simply the HPV vaccination.
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 cancers, with HPV-16 and HPV-18 subtypes the most dangerous.
In relation to cancer, plus 70% of cases are caused by HPV-16 or HPV-18, which is why these two subtypes are the targets of currently available vaccines.
HPV VACCINES ON THE MARKET
They exist on the market two distinct HPV vaccines. The quadruple vaccine, called Gardasil, currently available for free in the public health system in many countries, acts against subtypes 6, 11, 16 and 18. This vaccine thus protects against the human papillomavirus subtypes that cause cancer and more 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.
In Brazil, since the beginning of 2014, the Ministry of Health has made available on the NHS to quadruple vaccine for girls between 9 and 13 years old.
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 vaccination will bring real benefits 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 anal tumors are 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 sex 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 and women under 26 can not use the private health 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 holding 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, due to lack of studies proving their 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 experience, vaccination has an efficiency of almost 100% in the prevention of malignant tumors 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 effectiveness 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. Importantly, the vaccine is to prevent HPV and not to treat it.
Currently, we do not know how long the vaccine confers immunity. How 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 studies.
Contrary to what occurs in many infectious diseases, there are no post-vaccination serological tests for HPV, or blood tests that serve to measure the blood concentration of antibody against human papillomavirus after vaccination.
Among the major scientific studies that prove the effectiveness of the HPV vaccine, we highlight 3 of them:
- The FUTURE II trial - A study published in the New England Journal of Medicine, with 12,000 women between 15 and 26 years, 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 first trial - also published in the New England Journal of Medicine. Study of 5,455 women aged 16 to 24 years, double-blind, randomized, multicenter, placebo-controlled study. The quadrivalent vaccine was 100% effective in preventing anogenital warts, vulvar and vaginal cancers, NIC1, CIN 2, CIN 3 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 93% efficacy 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 (after 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 any HPV type at the time of vaccination, with no effect of the vaccine on this infection already underway; and third because there are cases unusual, yes, 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 that every now and then circulate among the population, the HPV vaccine is 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, vaccination against HPV 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 months and years are reported several cases of mild side effects. But this does not mean that the vaccine is dangerous and should not be taken. Several other vaccines present in the immunization schedule for decades also feature frequent mild side effects.
Just as an example, an American study showed that between 2006 and 2013 were administered over 57 million doses of 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%), most have been 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-Barré syndrome.
Two side effects, however, seem to be more common in HPV vaccine than other vaccines syncope (fainting) and venous thrombosis. Yet, 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 coagulation disorders.
The low but real risk of fainting, it is suggested that the patient be at rest 15 minutes after vaccination.
