One of the more farcical moments of the 2011 presidential primary season came after Minnesota Rep. Michelle Bachmann attacked Texas Gov. Rick Perry for supporting a state program that vaccinated 11- and 12-year-old girls against the Human Papillomavirus (HPV), a common sexually transmitted infection that can lead to cervical cancer.
Perry had already abandoned his state’s school-based vaccination program to appease religious conservatives. But Bachmann knew he was still vulnerable, so she took to the TV talk shows to warn the citizenry that the HPV vaccine could cause not only sexual promiscuity but . . . brain damage! Her evidence consisted of a second-hand anecdote about a girl from Tampa who, in her words, “took that vaccine, that injection, and suffered from mental retardation thereafter.”
The vaccine’s safety was already well established at the time, and so was its effectiveness. Health authorities had recommended that all girls receive a three-dose regimen at age 11 or 12 to ensure that they’d be protected at whatever age they became sexually active. But it wasn’t yet clear what impact that effort would have. Could mass vaccination protect a generation of young women from infection? The answer—revealed in a new study from the Centers for Disease Control and Prevention—is a resounding yes.
In a study spanning eight years, CDC researchers compared women’s HPV infection rates for two four-year periods—one just before the vaccine reached the market (2003-2006), and one just after (2007-2010). For women 20 and older, the infection rate changed little between the two periods. But the study documented a dramatic shift among 14- to 19-year-olds, the first cohort targeted for routine early vaccination.
As this graph shows, that group’s infection rate fell by more than half between the two periods. During the “pre-vaccine era,” roughly 12% tested positive for the cancer-causing types of HPV. In the “vaccine era” of 2007 to 2010, only 5% tested positive.
The finding is all the more impressive when you consider that only a third of 13- to 17-year-old girls had received the full three-dose regimen by 2010. Roughly half had received at least one dose, suggesting that even partial vaccination may reduce the risk of infection.
Vaccination rates have risen steadily since the vaccine hit the market in 2006, but the U.S. still lags far behind other countries. Rwanda has achieved 90% coverage, according to CDC officials, and many European countries have reached the 80% range.
The ultimate payoff, here and abroad, will be tens of thousands of cancers averted and lives saved. As for promiscuity and “retardation,” the new results show no cause for concern. The overall level of sexual activity didn’t change between the two periods, and there is still no evidence that the vaccine is scrambling people’s brains (except in some political circles).
Geoffrey Cowley