A two-dose regimen of the Cervarix HPV vaccine in girls remained noninferior to the three-dose regimen in young women 3 years after vaccination, according to researchers.
The findings complete a study that previously showed the two-dose Cervarix (2vHPV, GlaxoSmithKine) regimen was noninferior after 1 month, they wrote in The Journal of Infectious Diseases.
“These results support the use of the two-dose schedules for HPV vaccination in adolescent girls,” the researchers wrote. “Availability of both of these two-dose schedules [at 6-month and 12-month intervals] makes it more convenient for the subject, the prescriber and mass vaccination campaigns.”
Cervarix protects against HPV types 16 and 18, which cause about 70% of cervical cancer cases worldwide, according to WHO.
The phase 3b, open-label trial was conducted at facilities in Canada, Germany, Italy, Taiwan and Thailand between 2011 and 2014. In all, 1,285 patients completed the study up to a 3-year follow-up visit after the last dose.
Girls aged 9 to 14 years were randomly assigned to receive two doses 6 months apart (2D_M0,6) or two doses 12 months apart (2D_M0,12). In all, 506 girls were assigned to 2D_M0,6, and 378 to 2D_M0,12.
Another 401 female patients — aged 15 to 25 years — received a three-dose regimen, with doses coming at baseline, 6 months and 12 months (3D). They served as the control group.
For HPV type 16, the difference in seroconversion between the 3D and 2D_M0,6 groups was 0% (95% CI, –1.15 to 0.84). The geometric mean titer (GMT) ratio was 1.1 (95% CI, 0.97-1.24).
For HPV type 18, the seroconversion difference between the same two groups was –0.06% (95% CI, –1.37 to 0.96). The GMT ratio was 0.98 (95% CI, 0.85-1.13).
The results of comparisons between the 3D and 2D_M0,12 groups were similar. For HPV type 16, the seroconversion difference was 0% (95% CI, –1.15-1.12), whereas the GMT ratio was 0.85 (95% CI, 0.74-0.97).
For HPV type 18 among those two groups, the seroconversion difference was –0.28% (95% CI, –1.58 to 0.79), and the GMT ratio was 0.69 (95% CI, 0.59-0.8).
When the 2-day regimens were compared with each other, the results were similar again. For HPV type 16, the seroconversion difference was 0% (95% CI, –0.84 to 1.12), and the GMT ratio was 0.78 (95% CI, 0.69-0.87). For HPV type 18, the seroconversion difference was –0.22% (95% CI, –1.22 to .86), whereas the GMT ratio was 0.70 (95% CI, 0.62-0.80).
The researchers previously published similar results among the same cohorts at 1 month after the last dose.
They concluded at the time that the two-dose regimen could make HPV immunization more efficient.
“Reduced dose schedules of HPV vaccines may facilitate vaccination implementation and reduce cost, allowing for higher vaccination coverage and potentially more girls being protected from cervical cancer,” they wrote. – by Joe Green
Huang L, et al. J Infect Dis. 2017;doi:10.1093/infdis/jix154.
Puthanakit T, et al. J Infect Dis. 2017;doi:10.1093/infdis/jiw036.
Disclosure: Huang reports receiving grants through his institution from GlaxoSmithKline, consultancy fees for serving on the HPV expert board and payment for educational representation from GlaxoSmithKline. Please see the full studies for a list of all other authors’ relevant financial disclosures.