Can fewer doses of HPV vaccine provide immunity?

2013

Challenge

The human papillomavirus (HPV) vaccine is safe and effective, but completion rates of the recommended three-dose schedule are lower in low-income or difficult-to-treat populations. In 2011, IRP researchers reported that receiving two doses and even one dose of the vaccine did not alter the incidence of HPV 16/18 infection over a four-year study period. However, the precise strength and duration of vaccine response remained unknown.

Advance

IRP investigator Mahboobeh Safaeian, Ph.D., and colleagues confirmed that two or, in some cases, just one dose of the HPV 16/18 vaccine induced a robust and sustainable immune response as measured by antibody levels among women in the NCI Costa Rica Vaccine Trial. Although the women who received just one dose of the vaccine had lower antibody levels than participants who received all three doses, antibody levels remained stable up to 48 months after vaccination, and they were five times higher than levels in women who were unvaccinated but had antibodies from natural infection.

Impact

If confirmed, these findings could support modified vaccine administration schedules that may be cheaper, simpler, and more likely to be implemented around the world. Because long-term (more than 10 years) durability of antibody response and protection are needed, efforts to extend these findings beyond four years are underway.

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