The human papillomavirus (HPV) vaccine, approved in 2006, protects against strains of the virus responsible for 70% of cervical cancers. But what about the remaining 30%?
It turns out that those strains circulate more frequently among African-American and non-white Hispanic women, meaning that even if they are properly immunized, these populations aren’t protected against the sexually transmitted virus and the cancer it can cause.
Researchers led by Dr. Cathrine Hoyo, Associate Professor of Obstetrics and Gynecology at Duke University Medical School, believe that could explain why these women are more likely to contract HPV and have a higher cervical cancer mortality rate than white women, despite the fact that they tend to get screened for the cancer more regularly. Prior to the study, says Hoyo, it wasn’t clear whether the immune systems in African American women did not respond as potently against HPV or whether the virus that was infecting these women was different. Based on her results, presented at the American Academy of Cancer Research, it’s likely the latter.
Hoyo says that the HPV subtypes included in the existing two HPV vaccines — Gardasil, developed by Merck, and Cervarix, made by GlaxoSmithKline — are most common among white women but are significantly less common in non-white women. Within Hoyo’s trial, 65% of white women with HPV had the subtypes known as 16 or 18 , while only 36% of African-American women did. That means African-American women are only half as likely to get the type of HPV against which the vaccine works.
The findings highlight the complex role that race plays in medicine, especially as genetic studies reveal more biological reasons behind why racial and ethnic groups may have different propensities for disease, and respond in varying ways to drugs. “We don’t like to admit that race and ethnicity count, but they certainly do in the distribution of infectious diseases,” says Dr. Arthur Caplan, a bioethicist at the University of Pennsylvania. “Not to sound like a dope, but when [race] matters it matters.”
HPV infection is hardly the first disease to be linked to race. Tay-Sach’s is more common in Ashkenazi Jews, sickle-cell anemia is found mostly in Mediterranean or African populations, and cystic fibrosis has a higher incidence among people with Irish or English ethnicity. But all of those conditions are driven by genetic mutations that can be detected through testing. What makes the HPV findings trickier is the fact that the vaccine is designed to protect women before they become infected, and there is no way to tell which strains a woman will get — except, as Hoyo’s findings suggest, by her race.
That suggests that medical predictions should be based on some type of racial profiling; is it ethical to recommend different vaccines for different women based on race?
Caplan doesn’t think so, but not because of political correctness. Instead, he cautions that race, from a medical perspective, is much more complicated than physical appearance. “The HPV situation is a reminder that race does count, but it also should remind us that the categories we’re using aren’t even the right ones to manipulate,” he says, referring to the fact that race as defined on a societal level is different from race defined biologically, by a set of genes that are more common among people who share the same racial background. “We have a physical definition of race; when we see people from India and China, we call them ‘Asian,’ but there’s no way they do that in China.” At this point, it’s not even clear, he says, whether it’s possible to create clearly delineated genetic or biologic categories of race.
In response to the latest findings, Dr. Liana Clark, a medical director for Merck vaccines who helped develop Gardasil, said that in her studies the HPV vaccine had identical results in both African-American and white women. She acknowledged that different populations may be more likely to contract different subtypes, but says that the HPV strains in the vaccine were chosen because studies showed that the subtypes 16 and 18 are responsible for 70% of cervical cancers. “We may have different types,” Clark says, “but that doesn’t mean that our cervical cancers are caused more by these other types than by 16 or 18.” Hoyo acknowledges that in her study, she did not correlate the difference in strains to a change in the prevalence or mortality from cervical cancer among vaccinated white and African-American women.
“Black women have more invasive cervical cancer, and they die from it more often,” Clark says. “and those types are still caused by 16 and 18.”
Hoyo is still convinced that cervical cancer in African-American women may be caused by subtypes other than 16 and 18, which means many women may be unprotected, even if they are vaccinated. “Is it possible that the reason we are missing these women and they end up showing up with cervical cancer is because they don’t carry those very-high risk strains?” she says. “They’re told ‘oh there’s nothing, go home.'”
She hopes to see the next generation of HPV vaccines include additional strains of HPV, so that the the shots can protect against more than the 70% of cervical cancers caused by the most common forms of the virus. “I don’t want Merck to think that they did a bad job, because they didn’t,” she says. “Maybe it’s that they’re a victim of their own success, because now we’re moving beyond 16 and 18.” Lauri Markowitz, a CDC scientist, wrote in an email response that protecting against more strains would protect a broader group of women and potentially make the vaccine even more effective as a barrier against cancer.