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HPV4 vaccine safe, effective 8 years post-vaccination
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Three doses of quadrivalent HPV vaccine provided protection against disease and persistent infection for more than 8 years, according to recent study findings.
“With the publication of these study findings, the final piece of the HPV4 vaccine puzzle has been completed. The vaccine has been established as extremely durable — for 8 years now!” said study researcher and Infectious Diseases in Children Editorial Board member Stan L. Block, MD, FAAP. “This gets the primary HPV4 vaccine target population of 11- to 12-year-old patients (and up to aged 15) almost past the age of highest risk for sexual acquisition of this toxic and complex cancer-causing virus. With certainty, data have shown that the vaccine will keep vaccinees protected beyond 19 to 23 years old. Furthermore, a 10-year duration study for HPV4 vaccinees is currently being completed.”
Stan L. Block
Daron Ferris, MD, of Georgia Regents University in Augusta, Ga., and colleagues determined serological levels and vaccine effectiveness of HPV4 (Gardasil, Merck) 8 years following vaccination. Sexually naive children aged 9 to 15 years received either HPV4 vaccine (n=1,179) or saline placebo (n=482) at day 1 and months 2 and 6. At month 30, the placebo group received HPV4 vaccine following the same regimen. Both groups were followed through month 96. Children who were aged 16 years and older were eligible for effectiveness evaluations.
None of the children who received HPV4 vaccine at a mean age of 12 years developed disease or persistent infection caused by vaccine serotypes (HPV6/11/16/18) that lasted longer than 12 months. Children who received HPV4 vaccine at month 30 (at a mean age of 15 years) had a baseline seropositivity rate to one or more of the four HPV types similar to those vaccinated at day 1 (1.7% vs. 1.9%). However, four out of nine children vaccinated at the later age were seropositive to three vaccine types, which researchers said indicated previous HPV exposure.
Children aged 16 years and older had an estimated one new sexual partner per year.
No new serious adverse events occurred 8 years post-vaccination, according to Ferris and colleagues.
“The HPV4 vaccine administered to preadolescents and adolescents demonstrated durability in clinically effective protection and sustained antibody titers over 8 years… These long-term follow-up data, along with other extensive preapproval safety surveillance data, should help to encourage practitioners and reinforce national recommendations for HPV vaccination of all preadolescents and young adolescents,” the researchers concluded.
According to Block, three milestones must be achieved for any new vaccine that prevents a serious, common disease to gain complete trust among practitioners. First is safety. More than 30 studies have carefully evaluated the safety and tolerability of HPV4 vaccine. Overall, no vaccine-related major short term or long term adverse effects have been shown, either in comparative clinical trials or in large scale population observational studies.
Second is effectiveness. HPV4 has been shown to be almost 100% effective in preventing disease for young adult and adolescent females and males by the vaccine-included strains.
“Data also shows an overall intent-to-treat effectiveness of nearly 70% to 75% in a general population on average for all pre-cancers and cancers caused by HPV. Because the three-dose post-vaccine antibody concentrations are about twofold higher in 9- to 15-year-old patients than in this older female population, this antibody surrogate marker highly suggests that HPV4 should be similarly protective in pre-teens,” Block told Infectious Diseases in Children.
Third is durability, according to Block: “Are younger vaccinated patients, aged 9 to 15 years, in need of further doses to maintain protection? The study findings show no cases of breakthrough HPV4-type disease or persistent infection (12 months or longer) in any of these 429 younger patients in this long-term follow-up study.”
Block added that physicians should inform patients and parents that HPV4 vaccination prevents cancer of four different anogenital tract cancers, and possibly for oral cancers.
“Insist that your age-appropriate patients receive the vaccine. Do not be wishy-washy in your explanations. You now have all the verbal tools you need to vaccinate all but the most ardent nay-sayers and science deniers.”
Disclosure: Block and others report financial ties with Merck, who funded the study, and GlaxoSmithKline.
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