HPV vaccination prevented cervical lesions among young women, particularly those vaccinated when aged 15 to 26 years, according to a metanalysis of 26 studies published in Cochrane Library.
The vaccines also did not appear associated with an increased risk for side effects.
Cervical cancer is the third most common cancer among women worldwide. In 2008, about 530,000 women developed cervical cancer and about 275,000 died of the disease.
“The recognition of the strong causal association between HPV infection and cervical cancer has resulted in the development of HPV assays to detect cervical cancer precursors, and even vaccines that prevent HPV infection (prophylactic vaccines) or that treat HPV-induced lesions (therapeutic vaccines),” Marc Arbyn, MD, MSc, first author on the review and coordinator of the unit of cancer epidemiology at the Belgian Cancer Center and Scientific Institute of Public Health in Belgium, and colleagues wrote.
Several reviews have tried to summarize results from phase 2 and phase 3 trials in this setting; however, none combined information on all of the available endpoints, according to the researchers.
Arbyn and colleagues pooled data from 26 studies of 73,428 women conducted across all continents over the last 8 years. The analysis primarily included women aged younger than 26 years, but three trials enrolled women aged 25 to 45 years.
The review evaluated evidence for two vaccines — the bivalent vaccine (Cervarix, GlaxoSmithKline) targeting HPV16 and HPV18 and the quadrivalent vaccine (Gardasil, Merck) targeting HPV16 and HPV18 and two low-risk HPV types causing genital warts. Researchers did not include data on the newer HPV vaccine that targets nine HPV types.
“The nine-valent HPV vaccine has been shown to be highly effective and also very safe. However, because the duration of follow-up is shorter than that included in the current analysis the investigators appropriately did not include this strategy in the study,” Maurie Markman, MD, president of medicine and science at Cancer Treatment Centers of America and a HemOnc Today Editorial Board Member, told HemOnc Today.
Development of cervical precancer lesions served as the primary outcome, as none of the studies had long enough follow-up to assess the effect of HPV vaccination on cervical cancer risk.
Among women who did not have HPV at enrollment, about two in 10,000 who received the vaccine went on to develop cervical precancer compared with 164 in 10,000 women who received placebo.
In another analysis of all enrolled women aged 15 to 26 years — regardless of whether they had high-risk HPV at vaccination — vaccination reduced risk for cervical precancer associated with HPV16 or HPV18 from 341 per 10,000 women to 157 per 10,000 women. Vaccination also reduced the risk for any precancer lesions (559 per 10,000 vs. 391 per 10,000).
Among both the vaccinated group and the placebo group, the risk for serious side effects was about 7%.
“The committee concluded that the risk-benefit profile of prophylactic HPV vaccines remains favorable and expressed its concerns about unjustified claims of harm that lack biological and epidemiological evidence, and which may affect the confidence of the public,” Arbyn said in a press release. “At the same time, the committee encouraged health authorities to continue surveillance and examination for potential adverse events.”
Further research is needed on potential rare side effects and long-term cervical cancer prevention, according to the researchers.
“Regarding further research related to ‘safety,’ we must always be aware of possible side effects to all medical interventions,” Markman said. “However, the extensive existing data are crystal clear: HPV vaccination is a very safe and highly effective strategy that will substantially reduce the risk for HPV-associated disease, including cervical cancer.”
A recent study showed that 63% of girls and 50% of boys had initiated HPV vaccination. Many providers and patient groups are interested in increasing vaccination rates, another study shows.
“It is difficult to know what to say about increasing vaccination rates,” Markman said. “The existing data are simply overwhelming in their quality and in the demonstrated efficacy and safety of HPV vaccination. Hopefully, parents who for whatever reason have not accepted the tremendously positive impact of this approach to optimizing the future welfare of their children will become aware of this report and be open to a discussion of the benefits of vaccination.” – by Cassie Homer
For more information:
Maurie Markman, MD, can be reached at Cancer Treatment Centers of America in Philadelphia, 1331 East Wyoming Ave., Philadelphia, PA 19124.; email: firstname.lastname@example.org.
Disclosures: Arbyn reports travel grants from MSD-Sanofi-Pasteur and GlaxoSmithKline. Please see the study for all other authors’ relevant financial disclosures.