Silgard - papillomavirus vaccine

What is Silgard?

Silgard is a vaccine consisting of a suspension for injection containing purified proteins for four types of the human papillomavirus (types 6, 11, 16 and 18). It is available in vials or pre-filled syringes.

What is Silgard used for?

Silgard is used in patients aged nine years or older to protect against:

• precancerous lesions (abnormal cell proliferation) in the genital area (cervix, vulva or vagina) and cervical cancer, caused by certain cancerous types of human papilloma virus (HPV);
• external genital warts (genital warts) caused by specific types of HPV.

Silgard is administered according to official recommendations.
The vaccine can only be obtained with a prescription.

How is Silgard used?

Silgard is given to people at least nine years of age, in three doses, with an interval of two months between the first and second dose and a four-month interval between the second and third dose. If an alternative schedule is required, 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 should be administered within the one year period. It is recommended that once the first dose of Silgard is received, treatment is completed 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 papillomaviruses, some of which are associated with cancers of the genitals. HPV types 16 and 18 are responsible for approximately 70% of cervical cancer, while HPV types 6 and 11 cause approximately 90% of genital warts.
All papillomaviruses have an envelope, or "capsid", made up of proteins called "L1 proteins". Silgard contains purified L1 proteins for HPV types 6, 11, 16 and 18; these are produced by a method known as 'recombinant DNA technology', ie they are made by a yeast that has been given a gene (DNA) which makes it capable of producing L1 proteins. The 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 the 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) which stimulates a better response.

How has Silgard been studied?

Silgard has been studied in four main studies involving a total of around 21,000 women between the ages of 16 and 26. Silgard was compared with a placebo (a dummy vaccine). The studies looked at the number of women who developed genital lesions or warts attributable to HPV infection. Study participants were observed for approximately three years following 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 approximately 4,000 women aged 24 to 45 and observed the development antibodies against these types of HPV in approximately 1,700 girls and boys between the ages of nine and 15.

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 warts of types 6, 11, 16 and 18.
Looking at the results of all four studies together, among the more than 8,000 women vaccinated with Silgard who had never contracted an "HPV type 6, 11, 16 or 18 infection in the past, one developed a precancerous lesion. in the cervix which could have been attributable to HPV type 16 or 18. In contrast, 85 of the more than 8,000 women given placebo as a vaccine reported lesions resulting from these types of HPV. A similar effect of Silgard was found when the analysis also included cervical lesions due to the other two types of HPV (types 6 and 11).
Regarding external genital lesions attributable to HPV type 6, 11, 16 or 18 (including warts and precancerous lesions of the vulva or vagina), the results from three of the studies conducted were examined together. Two out of about 8,000 women in the Silgard group developed genital warts, while there were no reports of precancerous lesions of the vulva or vagina. In contrast, in the placebo group, a total of 189 cases of external genital lesions were detected in about 8,000 women.
Studies also showed that Silgard provided some level of protection against cervical injuries linked to other cancerous types of HPV, including type 31.
Additional studies confirmed Silgard's ability to protect against HPV injury and infection in women aged 24 to 45. Studies have also shown that the vaccine stimulates the production of sufficient amounts of antibodies against HPV in girls and boys between the ages of nine and 15.

What is the risk associated with Silgard?

The most frequently observed side effects associated with Silgard in studies (in more than 1 in 10 patients) are pyrexia (fever) and injection site reactions (redness, pain and swelling). For the full list of effects side effects detected with Silgard, see the package leaflet.
Silgard must not be used in people who may be hypersensitive (allergic) to the active substance or to any of the other ingredients. If signs of allergy occur after one dose of Silgard, the administration of the other doses of the 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 Silgard's benefits are greater than its risks in vaccination to prevent precancerous genital lesions (cervical, vulvar and vaginal), cervical cancer and injuries external genitalia (condyloma acuminata) caused by HPV types 6, 11, 16 and 18. The committee therefore recommended the granting of a marketing authorization for Silgard.

Other information about Silgard:

On 20 September 2006, the European Commission granted Merck Sharp & Dohme Ltd a "Marketing Authorization" for Silgard, valid throughout the European Union.
For the full version of Silgard's EPAR, click here.

For more information about Silgard therapy, read the package leaflet (included with the EPAR) or contact your doctor or pharmacist.
Last update of this summary: 07-2010.

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