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Dos dosis de vacuna HPV suficientes

"En el nuevo estudio, los investigadores compararon las respuestas inmunitarias de 830 personas divididas en tres grupos: las niñas de 9 a 13 años que recibieron dos dosis de la vacuna contra el VPH separados seis meses, las niñas de la misma edad que recibieron tres dosis durante seis meses, y las mujeres entre 16 y 26 años que recibieron tres dosis de más de seis meses. Todos los participantes recibieron la vacuna Gardasil, que protege contra cuatro cepas del virus."

....

"Si dos dosis en niñas generan el mismo tipo de respuesta inmune en tres dosis en las mujeres, se puede inferir que las niñas podrían ser protegidos de la enfermedad, incluso si usted no mide resultados de la enfermedad en las niñas", dijo Kahn.

"Un mes después de la última inyección contra el VPH , las niñas que recibieron dos dosis de la vacuna tenían aproximadamente la misma respuesta inmune como las niñas que recibieron tres dosis."

"Sin embargo, dos o tres años después de la vacunación, las niñas que recibieron dos dosis tuvieron una respuesta inmune reducida a las cepas VPH 18 y 6 en comparación con los que recibieron tres dosis."

El trabajo está publicado en JAMA el 30 de abril de 2013

*Immunogenicity of 2 Doses of HPV Vaccine in Younger Adolescents vs 3 Doses in Young Women. A Randomized Clinical Trial*

Simon R. M. Dobson; Shelly McNeil; Marc Dionne; Meena Dawar; Gina Ogilvie; Mel Krajden; Chantal Sauvageau; David W. Scheifele; Tobias R. Kollmann; Scott A. Halperin; Joanne M. Langley; Julie A. Bettinger; Joel Singer; Deborah Money; Dianne Miller; Monika Naus, MD; Fawziah Marra; Eric Young.

JAMA. 2013;309(17):1793-1802. doi:10.1001/jama.2013.1625.

Importance: Global use of human papillomavirus (HPV) vaccines to prevent cervical cancer is impeded by cost. A 2-dose schedule for girls may be possible.

Objective: To determine whether mean antibody levels to HPV-16 and HPV-18 among girls receiving 2 doses was noninferior to women receiving 3 doses.

Design, Setting, and Patients: Randomized, phase 3, postlicensure, multicenter, age-stratified, noninferiority immunogenicity study of 830 Canadian females from August 2007 through February 2011. Follow-up blood samples were provided by 675 participants (81%).

Intervention: Girls (9-13 years) were randomized 1:1 to receive 3 doses of quadrivalent HPV vaccine at 0, 2, and 6 months (n = 261) or 2 doses at 0 and 6 months (n = 259). Young women (16-26 years) received 3 doses at 0, 2, and 6 months (n = 310). Antibody levels were measured at 0, 7, 18, 24, and 36 months.

Main Outcomes and Measures: Primary outcome was noninferiority (95% CI, lower bound >0.5) of geometric mean titer (GMT) ratios for HPV-16 and HPV-18 for girls (2 doses) compared with young women (3 doses) 1 month after last dose. Secondary outcomes were noninferiority of GMT ratios of girls receiving 2 vs 3 doses of vaccine; and durability of noninferiority to 36 months.

Results: The GMT ratios were noninferior for girls (2 doses) to women (3 doses): 2.07 (95% CI, 1.62-2.65) for HPV-16 and 1.76 (95% CI, 1.41-2.19) for HPV-18. Girls (3 doses) had GMT responses 1 month after last vaccination for HPV-16 of 7736 milli-Merck units per mL (mMU/mL) (95% CI, 6651-8999) and HPV-18 of 1730 mMU/mL (95% CI, 1512-1980). The GMT ratios were noninferior for girls (2 doses) to girls (3 doses): 0.95 (95% CI, 0.73-1.23) for HPV-16 and 0.68 (95% CI, 0.54-0.85) for HPV-18. The GMT ratios for girls (2 doses) to women (3 doses) remained noninferior for all genotypes to 36 months. Antibody responses in girls were noninferior after 2 doses vs 3 doses for all 4 vaccine genotypes at month 7, but not for HPV-18 by month 24 or HPV-6 by month 36.

Conclusions and Relevance: Among girls who received 2 doses of HPV vaccine 6 months apart, responses to HPV-16 and HPV-18 one month after the last dose were noninferior to those among young women who received 3 doses of the vaccine within 6 months. Because of the loss of noninferiority to some genotypes at 24 to 36 months in girls given 2 doses vs 3 doses, more data on the duration of protection are needed before reduced-dose schedules can be recommended.

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Admin Eusalud