New study clarifies safety issues of Gardasil HPV vaccine


2012-10-02 15:01

Human papillomavirus (HPV) causes cervical cancer in women. The Gardasil vaccine, manufactured by Merck protects against four strains of HPV, which account for approximately 70% of cervical cancer cases in women. Gardasil was approved in 2006, after studies showed it was safe for use in females ages 9 to 26.

However, because studies conducted before a vaccine's approval are usually too small to detect rare side effects, researchers have continued to monitor the safety of the HPV vaccine. A new study published online on October 1 in the journal Archives of Pediatrics & Adolescent Medicine evaluated risk factors for the vaccine.

Researchers affiliated with the Kaiser Permanente Vaccine Study Center (Oakland, California) evaluated 189, 629 females who received at least one dose of Gardasil. The girls and young women received a total of 350,000 doses of the HPV vaccine between 2006 and 2008. The researchers calculated the annual rate of each side effect they observed. The main outcome measures were emergency department visits and hospitalizations.

The investigators found that fainting was six times more likely to occur on the day of vaccination, compared with a period many months after vaccination. They found 24 cases of fainting per 1,000 subjects on the day of vaccination, compared with an average of four cases per 1,000 subjects during a time period months after vaccination. In addition, skin infections were nearly twice as likely to occur within two weeks of vaccination compared with many months after vaccination. The researchers found that 3.5 cases of skin infections per 1,000 females occurred during the two weeks after vaccination, compared with 2.2 cases per 1,000 females during the comparison time period.

Because these side effects were somewhat expected, and the study did not find any new safety concerns, the authors wrote that their findings “support the general safety of routine vaccination.”

Take home message:
This study should reassure individuals who have received Gardasil or are considering vaccination. It should also reassure the parents of these individuals. Cervical cancer is curable when caught early and preventable both by safe-sex practices and the HPV vaccine. The HPV virus also can cause oral cancer in individuals who engage in oral-genital sex. Significant controversy has arisen regarding the administration of the vaccine to teens. One argument was that the vaccine would lead to increased sexual activity among adolescents who had received it. However, a study, published in the January issue of The American Journal of Preventive Medicine, should put those fears to rest. The study, which was conducted by researchers at the Centers for Disease Control and Prevention (CDC), reported that girls ages 15 to 19 who are vaccinated against HPV are no more likely to be sexually active or to have more partners than unvaccinated girls.

Reference: Archives of Pediatrics & Adolescent Medicine