Serious Reported Adverse Effects with Gardasil (HPV Vaccine)
Questions on Efficiency as well as Safety in Use of HPV Vaccine
The FDA licensed the quadrivalent human papillomavirus recombinant vaccine (Gardasil; Merck & Co, Inc) for females 9 to 26, to prevent infection with genital human papillomavirus (HPV) types 6, 11, 16, and 18. The Advisory Committee on Immunization Practices then recommended Gardasil for routine vaccination of girls 11 to 12 years old. HPV types 16 and 18 cause an estimated 70% of cervical cancers worldwide, and are responsible for most HPV-induced anal, vulvar, vaginal, and penile cancer cases. HPV types 6 and 11 cause an estimated 90% of genital warts cases.
Gardasil was licensed for use in the United States in June 2006, and the Advisory Committee recommended routine vaccination of girls aged 11 to 12 years later that same month. However, the first phase 3 trials of the HPV vaccine with clinically relevant end points–cervical intraepithelial neoplasias grades 2 and 3 (CIN 2/3)–were not reported until May 2007. Previously only reduction in the prevalence of persistent infection and CIN from the 2 virus strains included in the vaccine had been reported. The results were promising, but serious questions regarding the overall effectiveness of the vaccine for protection against cervical cancer remained to be answered (including how long immunity will last), and more long-term studies were called for. Some data from the clinical trial indicated immune molecules may wane after three to five years.
Although a major killer in the developing world, particularly in Africa, where the vaccines are too expensive for use, cervical cancer is classified as very rare in the West because it is almost always preventable through regular Pap smears, which detect precancerous cells early enough for effective treatment. Indeed, because the vaccines prevent only 70 percent of cervical cancers, Pap smear screening must continue anyway.
Other independent experts worry that eliminating the two cancer-causing HPV strains covered by Gardasil and Cervarix might allow the other cancer-causing strains of HPV to increase in frequency, reducing the vaccine’s effect.
The Center for Disease Control asks health care centers to report side effects through its Vaccine Adverse Events Reporting System (VAERS) – a national, voluntary, passive surveillance system, following AEFIs (Adverse Effects Following Immunization). Although there are limitations to the VAERS, such as its voluntary nature (which could lead to false reporting or underreporting) and the inability to prove causality, there have been a substantial number of reports of patients experiencing adverse events after receiving the vaccine (about 21,100 reports as of July 2011). As of data from December 31, 2008, about ninety-four percent of the reported AEFIs were not serious, ranging from arm pain to fainting, but 6.2 percent were classified as serious.
Serious Adverse Events reported included anaphylaxis, Guillain-Barre Syndrome, transverse myelitis, pancreatitis, and venous thromboembolic events (VTEs). Most of the AEFI rates were not greater than the background rates compared with other vaccines, but there was disproportional reporting of syncope and venous thromboembolic events. The significance of these findings must be tempered with the limitations (possible underreporting) of a passive reporting system.
There is at least one verified case of auto-immune initiated motor neuron disease declared triggered by Gardasil (presented by neurologists at the 2009 American Neurological Association meeting in Baltimore, MD).
A researcher from the Interbalkan European Medical Center in Thessaloniki, Greece, told Medscape Neurology that her team is questioning whether the immuno-stimulatory properties of the human papillomavirus-like particles of the vaccine are triggering adverse effects in vulnerable patients.
Recently, in an issue of Multiple Sclerosis, researchers from St. Vincent’s Hospital in New South Wales, Australia reported 5 cases of multiple sclerosis after vaccination with the drug. The group reported in January that patients presented with multifocal or atypical demyelinating syndromes within 21 days of immunization.
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