Human papillomavirus (HPV) is a sexually transmitted virus. At least 70 percent of sexually active persons will be infected with genital HPV at some time in their lives. HPV infects both men and women. Since the virus can be silent for many years, a person can have genital HPV even if years have passed since he or she had sex.
There are three groups of genital HPV strains:
1. Many no-risk types cause neither warts nor cancer;
2. A few types cause genital warts;
3. 15 or so high-risk types can increase one's risk of cancer.
If left untreated, genital warts do not turn into cancer.
High-risk HPV, on the other hand, may trigger an infection that leads to cervical cancer. The majority of infections with high-risk HPVs clear up on their own. Some infections persist without causing any additional abnormal cell changes. However, a few infections caused by high-risk HPVs end up triggering cervical cancer over many years.
Basic Mechanism
The HPV sits inside the epithelial cells housed in a protective shell made of a viral protein called L1. After the virus enters the cell, the viral coat is degraded, leading to the release of the virus' genetic material into the cell and its nucleus. From the nucleus, the genes of the virus are expressed, including two genes called E6 and E7, which instruct the cell to build viral proteins called E6 and E7. These then disable the normal activities of the woman's own suppressor genes, which make suppressor proteins that do "damage surveillance" in normal cells. Even after suppressors are disabled in a woman's cervical cells, it usually takes more than 10 years before the affected tissue becomes cancerous.
What does the vaccine do
HPV vaccine, like the real human papillomavirus, have the same outer L1 protein coat, but they have no genetic material inside. This structure enables the vaccine to induce a strong protective immune response.
The vaccination protects a person from future infection by the HPV high-risk types that can lead to cancer. It is not a vaccine against cancer itself. A person receives a series of three shots over a 6-month period.
Pap tests still a necessity
After the vaccination, a woman must still get routine Pap tests or another approved cervical cancer screening test. Although the anti-HPV vaccine prevents infection by the dominant HPV types, which are responsible for 70 percent of the cervical cancer cases, it does not prevent infection by most of the other types that can also cause cervical cancer. A Pap test can detect abnormal cervical growth regardless of what HPV type caused it to develop.
Future
Studies are under way to determine if a booster, in addition to the three initial intramuscular injections, will be necessary for long-term protection. Clinicians know that the new cancer vaccine remains effective for up to at least 4 years, but more research is needed to find out what happens after that time.
Available vaccines in India
MSD Pharmaceuticals (India ), the local affiliate of Merck & Co., Inc USA
Fainting is more common among adolescents receiving the Gardasil vaccine than in other kinds of vaccinations. Patients should remain seated for 15 minutes after they receive the HPV vaccine. General side effects of Gardasil may include joint and muscle pain, fatigue, physical weakness and general malaise.
Gardasil cannot be taken if you have or have had an allergic reaction after getting a dose of Gardasil or a severe allergic reaction to yeast, amorphous aluminum hydroxyphosphate sulfate, polysorbate.
Gardasil is not recommended for use in pregnant women, have immune problems, like HIV infection, cancer, or you take medicines that affect your immune system, have a fever over 100°F (37.8°C)
Gardasil is a shot that is usually given in the arm muscle. Three shots are given on the following schedule:
• Dose 1: at a date you and your health care provider choose.
• Dose 2: 2 months after Dose 1.
• Dose 3: 6 months after Dose
GlaxoSmithKline is also planning a large-scale launch its cervical cancer vaccine Cervarix in India
Cervarix is a vaccine against certain types 16 and 18, which currently cause about 70% of cervical cancer cases.
Cervarix is a preventative cervical cancer vaccine, not therapeutic. Cervarix vaccine will not block infection from cervical cancer-causing HPV strains other than HPV 16, 18, 31 and 45
Which is better
Both vaccines are against the human papilloma virus but Cervarix seems to be more effective against cancer cervix.
Cervarix can be given to females between 10 to 45 yrs old, whereas Gardasil can be given to females between 16 to 26yrs only
Both the vaccines are given in the schedule of 0,1,6 months. Cervarix is the costlier one being priced at Rs.3200 per dose. Cervarix seems to win against Gardasil because of its stronger immune response and broader protection.
