Reduced HPV vaccine doses may be adequate

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1. Immunogenicity in girls receiving 2 doses of the quadrivalent HPV vaccine was non-inferior to immunogenicity in young women receiving 3 doses at 7 months of follow-up. 

2. The non-inferiority of the 2 doses regimen for HPV-18 in comparison to 3 doses regimen, as measured by antibody responses, did not persist at 24 months, although the clinical implications of this is not clear. 

Evidence Rating Level: 1 (Excellent) 

Study Rundown: Immunogenicity for HPV-16 and HPV-18 in girls receiving 2 doses were non-inferior to women receiving the current standard 3 doses, as assessed at 7 months (titers 1 month after final dose). This shows promise for a more efficient dosing schedule, given the global burden of disease and high costs associated with the vaccine and its administration. In the future, younger girls (9-13 years old) may be able to receive 2 doses initially, in part due to their more robust immune response as compared to young women (16-26 years old). With cervical cancer being the second most common cause of cancer mortality in women, HPV control efforts could be bolstered by a reduced dosing protocol. Nonetheless, more work is needed in studying the duration of immune response and its clinical implications. In this study, non-inferiority of HPV-18 antibody protection in girls did not persist in the 2-dose group compared to the 3-dose group of girls at 24 months. Whether this reduced surrogate marker of protection has significance in propensity to contract disease, is unclear, as only a small amount of antibody should be needed at the epithelial mucosa to be effective. Studies with a larger sample and longer follow-up assessing actual disease prevalence would be needed to draw conclusions regarding the comparison of efficacy of the dosing schedules. This well-designed study may, however, guide policy perhaps in changing dosing schedule to an initial 2 doses in girls and an optional 3^rd dose in adolescence. Scheduling options in other populations such as sexually active young women and men should be examined as well.

Click to read the study, published today in JAMA

Click to read an accompanying editorial, published today in JAMA

Relevant Reading: Comparison of the immunogenicity and reactogenicity of a prophylactic quadrivalent human papillomavirus (types 6, 11, 16, and 18) L1 virus-like particle vaccine in male and female adolescents and young adult women

In-Depth [randomized study]: This study examined whether 2 doses of quadrivalent HPV vaccine, given 6 months apart to girls aged 9 -13 years, resulted in immune responses noninferior to the standard 3 doses in young women aged 16-26. There were 259 girls randomized to receive 2 doses of HPV vaccine at 0 and 6 months, while 261 girls and 310 women were randomized to receive 3 doses of the same at 0, 2 and 6 months. Geometric mean Titers (GMT) ratios for HPV-16 and HPV-18 in girls receiving 2 doses were non-inferior (1.77 to 2.24 fold higher GMT) to women receiving 3 doses at 7 months. For secondary outcome of incremental protection of 3^rd dose in girls, non-inferiority was demonstrated for HPV-16 and HPV-11 out to 36 months, however, HPV-18 responses at month 24 and HPV-6 at 36 months were no longer non-inferior.

By Mike Hoaglin and Rif Rahman

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