Even two doses of the HPV vaccine are good

The CDC recommends three doses of the HPV vaccine for teens. But in 2011, fewer than one-third of girls age 13-17 had been immunized. We shouldn’t let the perfect be the enemy of the good, though. And there’s some good news in the latest issue of JAMA:

Importance  Determining vaccine dose-level protection is essential to minimize program costs and increase mass vaccination program feasibility. Currently, a 3-dose vaccination schedule is recommended for both the quadrivalent and bivalent human papillomavirus (HPV) vaccines. Although the primary goal of HPV vaccination programs is to prevent cervical cancer, condyloma related to HPV types 6 and 11 is also prevented with the quadrivalent vaccine and represents the earliest measurable preventable disease outcome for the HPV vaccine.

Objective  To examine the association between quadrivalent HPV vaccination and first occurrence of condyloma in relation to vaccine dose in a population-based setting.

Design, Setting, and Participants  An open cohort of all females aged 10 to 24 years living in Sweden (n = 1 045 165) was followed up between 2006 and 2010 for HPV vaccination and first occurrence of condyloma using the Swedish nationwide population-based health data registers.

Main Outcomes and Measures  Incidence rate ratios (IRRs) and incidence rate differences (IRDs) of condyloma were estimated using Poisson regression with vaccine dose as a time-dependent exposure, adjusting for attained age and parental education, and stratified on age at first vaccination. To account for prevalent infections, models included a buffer period of delayed case counting.

This was a study of more than 1 million girls age 10 to 24 in Sweden. Of them, 926,119 were never vaccinated, 119,046 had one dose of vaccine, 112,555 had 2 doses, and 98,252 had three doses. Over the study period, 20,383 of them developed first-onset cases of genital warts.

Looking at adolescents age 10-16, those who had three doses had an incident rate ratio of only 18% compared to unvaccinated girls. Girls who received two doses had an IRR of 29%. Even one dose of vaccine led to an IRR of 31%. Getting one dose of vaccine prevented 384 cases of genital warts per 100,000 person-years. Two doses prevented 400 cases, and three doses prevented 459 cases. The differences there aren’t that big.

Yes, it would be nice if everyone got three doses. But even two doses provides a lot of protection. Heck, even one dose is helpful. This vaccine works. The effect of fewer doses on cancer isn’t known from this study, but it’s not crazy to think that fewer doses would still help in some way. Bottom line is that we should push for the recommended three doses, but it might be more important to get started than to finish.

Two more things. First, girls who got three doses and were vaccinated between 10-13 years of age, had an IRR of 8%. Vaccinating early matters. Second, this:

Vaccinate your kids, please.


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