What is Silgard?
Silgard is a vaccine, consisting of a injectable suspension containing purified proteins for four types of human papillomavirus (types 6, 11, 16 and 18). It is available in vials or in pre-filled syringes.
What is Silgard used for?
Silgard is used in patients aged nine or over to protect against:
- precancerous lesions (abnormal cell proliferation) in the genital area (cervix, vulva or vagina) and carcinoma of the cervix, caused by certain carcinogenic types of human papilloma virus (HPV);
- external genital warts (genital warts) caused by specific types of HPV.
Silgard is given according to official recommendations.
The vaccine can only be obtained with a prescription.
How is Silgard used?
Silgard is given to individuals at least nine years of age, in three doses, leaving an interval of two months between the first and second dose and an interval of four months between the second and third dose. If an alternative program is needed, the second dose should be administered at least one month after the first, and the third dose at least three months after the second; all doses must be administered within the period of one year. It is recommended that upon receipt of the first dose of Silgard, complete the treatment by taking all three doses. The vaccine is given by intramuscular injection, preferably in the shoulder or thigh.
How does Silgard work?
Papillomaviruses are viruses that cause warts and abnormal tissue growth. There are over 100 types of papillomavirus, some of which are associated with genital tumors. Types 16 and 18 of HPV are responsible for about 70% of cervical carcinomas, while types 6 and 11 of HPV cause about 90% of genital warts.
All papillomaviruses have an envelope, or "capsid", made up of proteins called "L1 proteins". Silgard contains purified L1 proteins for types 6, 11, 16 and 18 of HPV; these are produced with a method known as "recombinant DNA technology", ie they are obtained from a yeast in which a gene (DNA) has been inserted that makes it capable of producing L1 proteins. Proteins are collected in "virus-like particles" (ie structures that resemble HPV viruses, so that the body has no difficulty in recognizing them), unable to cause infection.
When a patient receives the vaccine, the immune system produces antibodies against L1 proteins. Following vaccination, the immune system is able to produce antibodies more quickly when exposed to real viruses. This will help protect against diseases caused by these viruses.
The vaccine also contains an "adjuvant" (a compound containing aluminum) that stimulates a better response.
What studies have been carried out on Silgard?
Silgard has been studied in four main studies out of a total of about 21, 000 women aged 16 to 26 years. Silgard was compared with a placebo (a dummy vaccine). Studies have considered the number of women who developed lesions or genital warts due to HPV infection. Participants in the studies were kept under observation for about three years after the third dose of the vaccine.
Additional studies examined Silgard's ability to prevent infection with HPV types 6, 11, 16 and 18 and related genital lesions in about 4, 000 women aged 24 to 45 years and observed development of antibodies against these types of HPV in about 1, 700 girls and boys aged nine to 15 years.
What benefit has Silgard shown during the studies?
Silgard was effective against precancerous genital lesions of the cervix, vulva and vagina, cervical cancer and HPV-related condylomas type 6, 11, 16 and 18.
Taking the results of all four studies together, among the more than 8, 000 women vaccinated with Silgard who had never had an HPV infection of type 6, 11, 16 or 18 in the past, one developed a precancerous lesion in the cervix that could have been attributable to HPV type 16 or 18. By contrast, 85 of the more than 8, 000 women who received a placebo as a vaccine reported injuries resulting from these types of HPV. A similar effect of Silgard was found when the analysis also involved cervical lesions due to the other two types of HPV (types 6 and 11).
With regard to external genital lesions attributable to HPV type 6, 11, 16 or 18 (including condyloma and precancerous lesions of the vulva or vagina), the results deriving from three of the studies conducted were examined together. Two of the approximately 8, 000 women in the Silgard group developed genital warts, while there were no cases of precancerous lesions of the vulva or vagina. By contrast, in the placebo group a total of 189 cases of external genital lesions were detected in around 8, 000 women.
Studies also showed that Silgard provided some level of protection against cervical lesions linked to other types of HPV carcinogens, including type 31.
Additional studies confirmed Silgard's ability to protect against HPV injury and infection in women aged 24 to 45 years. Studies have also shown that the vaccine stimulates the production of sufficient amounts of antibodies against HPV in girls and boys aged between nine and 15 years.
What is the risk associated with Silgard?
The most common side effects associated with Silgard in the studies (more than 1 in 10 patients) are pyrexia (fever) and reactions at the injection site (redness, pain and swelling). For the full list of all side effects reported with Silgard, see the Package Leaflet.
Silgard should not be used in people who may be hypersensitive (allergic) to the active substance or any of the other ingredients. If signs of allergy occur after a dose of Silgard, the administration of other doses of vaccine should be discontinued. Vaccination should be postponed in case of patients with high fever.
Why has Silgard been approved?
The Committee for Medicinal Products for Human Use (CHMP) decided that the benefits of Silgard outweigh the risks in vaccination aimed at preventing precancerous genital (cervical, vulvar and vaginal) lesions, cervical carcinomas and lesions external genitalia (condylomata acuminata) caused by HPV type 6, 11, 16 and 18. The committee therefore recommended the granting of the marketing authorization for Silgard.
More information on Silgard:
On 20 September 2006, the European Commission granted Silkard a marketing authorization valid for the entire European Union to Merck Sharp & Dohme Ltd.
For the full EPAR for Silgard, click here.
For more information about Silgard therapy, read the package leaflet (also part of the EPAR) or contact your doctor or pharmacist.
Last update of this summary: 07-2010.
