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Home » Anti-vaccine Gayle DeLong tries to correct her HPV vaccine article by blogging

Anti-vaccine Gayle DeLong tries to correct her HPV vaccine article by blogging

Last updated on August 17th, 2021 at 11:14 am

A few days ago, I wrote about a terrible, laughable anti-HPV vaccine article by Gayle DeLong, a tenured Associate Professor in the Department of Economics and Finance in the Zicklin School of Business, Baruch College/City University of New York. She has zero background, experience, knowledge, education, or credibility in vaccine science.

Her appalling article tried to convince the reader that the human papillomavirus (HPV) vaccine caused a decrease in their fertility. If this were a real article, I’d be appalled that it got published, but it was clearly a bad article with bad science, bad methodologies, and bad conclusions.

It failed basic scientific statistical analysis like accounting for confounding data. Furthermore, Gayle DeLong provided no convincing biologically plausible mechanism describing how the HPV vaccine could affect pregnancy rates. And her references were ridiculous – she cited Mark and David Geier, who can charitably be called charlatans who attempted to “treat” autistic children with a horrific and unethical procedure. And she actually mentioned Mark Geier in her acknowledgments.

Furthermore, she ignored the vast body of evidence, published by real scientists, not an expert in international finance, in real journals that the HPV vaccine is demonstrably safe. And in those huge studies, some with millions of patients, there was no detectable difference in fertility rates between vaccinated and unvaccinated individuals. This issue only exists in the mind of Gayle DeLong and other anti-vaccine activists.

I’ve read a bunch of anti-vaccine papers in my time, but this one may be one of the worst. All anti-vaccine papers are bad, that’s why they are rarely if ever, published in respected journals.

Criticism of Gayle DeLong

Several of us pointed out that the paper completely ignored an important issue – DeLong utterly failed to account for contraception rates in her article, an omission that should eventually get this article retracted. My snarky online pal Orac wrote about this “dumpster fire” of an article, and its lack of proper statistical analysis (see Note 1):

There’s also another huge problem with this study. One of the most important covariates that could impact pregnancy rates is (obviously) usage of contraception. Yet nowhere in the analysis is there a consideration of contraception usage. Yes, Delong brings up the lack of statistical significance of the results among never-married women by suggesting that maybe most of them want to avoid pregnancy (which could be true), but, again, contraceptive use is an incredibly important factor, which was not even included as a covariate.

My first thought was that maybe it was a question that wasn’t asked. It’s possible. Oh, wait. It’s not. The questionnaire asks whether a female has ever used oral contraceptives, if she is taking them now, and how long she’s taken them. So why did Delong not include oral contraceptive use in her analysis? She could have. She doesn’t even really discuss it other than discussion of contraceptive failure rates. I strongly suspect there was a reason for this.

I also strongly suspect that a correlation between HPV uptake and oral contraceptive use (which is not unreasonable to hypothesize) could explain the results Delong observed and that correcting for oral contraceptive use in the survey sample would likely have resulted in the results of the logistic regression no longer being statistically significant (emphasis mine). In fairness, if the correlation is not positive but negative (i.e., HPV vaccination is associated with less oral contraceptive use), the results could be more robust than what Gayle found.

In any case, I can see only two explanations for Gayle Delong’s not having done this analysis, given that the data appear to have been available. Either she was clueless and didn’t even consider it as a covariate, or she did some exploratory analyses and with contraceptive use included the effects that she saw disappeared.

After all, they weren’t very robust; so I suspect that it wouldn’t take much. I welcome comments from the epidemiologists who read this blog. After all, existing evidence largely contradicts Delong’s findings, with HPV vaccination having no effect on fertility except in one group. The group? In females with a history of sexually transmitted infections or pelvic inflammatory disease (i.e. a group at high risk of exposure to HPV infection), HPV vaccination made pregnancy more likely.

If you’re taking notes, these are critically important points. DeLong got it completely wrong, making the results borderline useless. This is an error so amateurish, it betrays her utter lack of experience and knowledge of even basic statistical analysis in epidemiology. But then again, Gayle DeLong does not even hit the minimum standards of epidemiology.

Gayle DeLong responds to Orac

Go get your popcorn and favorite libation, because DeLong decided to indirectly respond to Orac’s criticism of her paper (while ignoring mine, I’m hurt) by…blogging about it on a notorious anti-vaccine website.

The proper action would have been to contact the journal, withdraw the article, rewrite it, and then submit it for publication again. Or write a comment in PubMed. Or do anything but blog about it.

In an article published in the fake news website, Age of Lying About Autism, Gayle DeLong responded directly to the criticism. Instead of doing the proper thing and reworking her article after withdrawal, she “fixes” her article here:

In connection with my paper, the question has been raised: Given that married women who had the HPV shot were less likely to conceive than those who did not receive the shot, were the former more likely to use birth control than the latter? My result that married women who received the shot were less likely to conceive could be explained if those women were more actively trying to prevent pregnancy than married women who did not receive the shot.

The three questions on NHANES that provide insights into contraception are 1) SXQ251: In the past 12 months, how often had you had sex without a condom? 2) RHD442: Are you taking birth control pills now? 3) RHQ520: Are you now using Depo-Provera or injectables to prevent pregnancy?

I seek to determine whether married women who received the HPV shot are more actively seeking to prevent pregnancy than married women who did not receive the shot. I define “actively seeking to prevent pregnancy” as women who at the time of the interview were using condoms at least half the time or taking the birth control pill or receiving an injectable. I find 51.5% of married women who did not receive the shot and 36.6% of married women who received the shot were actively seeking to prevent pregnancy. The 14.9% difference is statistically significant at the 1% level.

This finding suggests that a greater percentage of married women who received the shot should be conceiving compared with married women who did not receive the shot. However, my original study finds that married women who received the shot are less likely to conceive than married women who did not receive the shot. The finding of my original study is not the result of married women who received the HPV vaccine actively avoiding pregnancy more than women who did not receive the HPV shot. I’m happy to discuss details of my results with researchers who are interested.

Setting aside the poor quality of using a “questionnaire” to determine a correlation between the vaccine and pregnancy rates, she actually fails to provide any convincing evidence of a difference between the populations.

And I don’t get how this matters – “I find 51.5% of married women who did not receive the shot and 36.6% of married women who received the shot were actively seeking to prevent pregnancy.” What is she trying to do? Prove that the HPV vaccine causes women to not want to get pregnant. That would be laughable.

Maybe she meant something else, but Gayle DeLong, a finance expert, doesn’t get epidemiology. Not even close. We picked on one confounder, but there are dozens of others that she completely ignored. Obesity, other diseases, smoking, or any number of other factors could have an impact on the fertility rate. It wasn’t just the contraception rate, for which she did not provide a convincing argument.

Let me be clear. She’s trying to claim, in this pseudo-update, that she corrected for contraceptive use. She did not. And she did not provide any evidence that if corrected for contraceptive use that there was a difference in pregnancy rate between the vaccinated and unvaccinated groups.

This is a bad article, and I stand by what I wrote before – it is a statistical mess, it provides no reasonable biological plausibility, and it lacks a thorough investigation of confounding variables. It does not show correlation, let alone causation.


This article by Gayle DeLong was finally retracted because it shows nothing about the safety (or effectiveness) of the HPV vaccine. It is nothing more than a propaganda piece for the anti-HPV vaccine crowd. DeLong’s recent comments do nothing to make anyone think that she actually considered all of the variables that might lead to the results she claimed she got.

DeLong has neither the credentials nor the knowledge to write an article that may make a few people decide to avoid a cancer-preventing vaccine. No, eating organic apples is not going to prevent cancer, but this vaccine will.

Orac’s and my criticisms still stand.


  1. Orac is about a billion times better with statistical criticisms than I will ever be. Orac needs to use statistics every day. I relied on statistics geeks throughout my career, although I’ve probably had 3 years of statistics, including a year’s course in a medical school. I admit it, I got lazy about stats.



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