Study Claiming Link Between HPV Vaccine, Pregnancy Rates Pulled

Ivan Oransky, MD

December 10, 2019

Following a barrage of criticism, a journal has retracted a paper that claimed a link between the human papillomavirus (HPV) vaccine and decreased pregnancy rates.

First published in June 2018 in the Journal of Toxicology and Environmental Health, Part A, the study, by Gayle DeLong of Baruch College's Zicklin School of Business in New York City, concluded that "if 100% of females in this study had received the HPV vaccine, data suggest the number of women having ever conceived would have fallen by 2 million."

Within days, however, the pseudonymous "Orac," a frequent critic of research linking vaccines to health problems, had posted a lengthy critique of the work. "Where it really gets interesting is the logistic regression including covariates in which the number of HPV shots received (one, two, or three) was related to the likelihood of getting pregnant," Orac wrote.

"In this model, almost none of the comparisons were statistically significant. The only two where there was a statistically significant result were for the full sample, one shot versus no shots and three shots versus no shots. To me this is a huge red flag that the results are not robust and that there is no dose-response observed."

Among other issues, Orac also noted that the study did not report on birth control use — a key confounder — in the women surveyed. DeLong responded on Age of Autism, a site that frequently posts content alleging the discredited claim that vaccines cause autism.

In March of this year, a journal published a letter from two researchers in Japan — where the HPV vaccine has been in use since 2009 but is the subject of heated debate — concluding that "the correlation observed between the HPV vaccination introduction and birth rate change in the United States was possibly spurious."

That was followed in August by comments on PubPeer, a site that allows for comments on published articles, by scientific sleuth Elisabeth Bik. Bik called the paper a "very flawed and biased study with the potential of being misinterpreted or misused." (Disclosure: The reporter of this story is a volunteer board member of the PubPeer Foundation, a nonprofit organization.)

"The paper looked at pregnancy rates in women who had or had not received the HPV vaccine," Bik told Medscape Medical News. "However, the study only included young women, aged 25-29. Many women, in particular those with a college education, will become pregnant for the first time at an older age, so 30 years or older."

But in the study, the groups of women who had the HPV shot and the women who did not receive it differed in education levels, Bik noted. In the HPV-vaccinated group, many more women had a college degree than in the unvaccinated group.

"By selectively focusing on younger women, under 30, and looking at pregnancy and HPV vaccination rates, the author's results appear to show that HPV-vaccinated women had a lower probability of pregnancy. But in reality, the HPV-vaccinated women with a college degree did not have their first baby yet. This is a classic example of a 'confounding factor,'" Bik said.

Today, the journal retracted the paper. "Following review and publication of the article, we were alerted to concerns about the scientific validity of the study," the journal writes in its retraction notice. "As a result, we sought advice on the methodology, analysis and interpretation from a number of experts in the field.

"All of the post-publication reports we received described serious flaws in the statistical analysis and interpretation of the data in this paper, and we have therefore taken the decision to retract it," the notice continues.

DeLong has not responded to a request for comment from Medscape Medical News.

The retraction "is the correct decision," Bik told Medscape Medical News. "This paper was used by many people to 'prove' that the HPV vaccine caused infertility in young women, but in reality the paper had some severe flaws. Although the author does not use the word 'infertility' to talk about the effects of the vaccine, her study has been used amongst anti-vaxx groups to 'show' that the HPV vaccine causes infertility. This made a lot of parents anxious [about getting] their kids vaccinated against HPV."

Bik said she hoped that the retraction could prevent some of those children from developing cervical and anal cancers that are linked to certain HPV strains.

Ivan Oransky, MD, is vice president of editorial at Medscape and co-founder of Retraction Watch. He is also Distinguished Writer in Residence at New York University's Arthur Carter Journalism Institute, and president of the Association of Health Care Journalists.

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