, 18 tweets, 7 min read Read on Twitter
Let's talk about a paper that I have seen quoted as "proving" that the HPV vaccine causes infertility.
Hint: It doesn't.
It is behind a paywall, so you definitely do not want to use SciHub to download it. 😀
Here is a screenshot of the abstract. Reading it, you might assume that the sole author analyzed data from 8 US million women, and you might think "wow, that is a big study".
But she only looked at 700 women. Much smaller than she wants us to believe. #Misleading.
DeLong first shows us this graph of declining pregnancy rates in women between 25-29 years old. There is no source listed, but this seems plausible. Women get kids at later age.
The sample set of the 700 women surveyed between 2007 and 2014 included 118 women who got the HPV shot and 582 who did not. This makes sense because the vaccine was only introduced around 2006.
The vaccine is typically given to teenage girls so if you interviewed women aged 25-29 between 2007-2014, most of them did not have the vaccine yet.
Here is a look at the demographics between vaccinated and un-vaccinated women. There are some interesting statistical differences between these 2 groups.
Most importantly, the women who had an HPV shot had higher chance of having a college degree (significant).
There was also a trend (albeit not significant) that they had a higher family income.
As a side note, the surveyed women appeared to be only 2.25 feet (67 cm) tall 😂
This difference in % college degrees and family income between the 2 groups could be a HUGE confounding factor in pregnancy rates in young women.
Rather, you could argue that women with higher education were more willing to be vaccinated against HPV, and they were also having children at a later age. That sounds much more plausible than claiming the vaccine causes infertility.
Take a look at this graph, published in the @nytimes about a year ago. Let me clearly state what it shows: women with college degrees get their first baby later than women without a college degree.
Source: nytimes.com/interactive/20…
@nytimes If you interview women aged 25-29 to look at pregnancy rates, that means you are deliberately leaving out women who did not have their first baby YET.
@nytimes The way the author carefully chose the age group to be limited to young women, together with the significant difference in % college degrees between vaccinated vs unvaccinated women suggests this is a very biased, non-scientific study.
@nytimes Also, make sure to read this other very critical review of this paper, written by the amazing Orac aka @gorskon :
@nytimes @gorskon In which Orac reveals that the lone author of this paper and the people she lists in the acknowledgments are active anti-vaxxers, who might have some bias in reporting certain results or leaving out other data.
@nytimes @gorskon Also note that the title of the paper states "A lowered probability of pregnancy in females in the USA aged 25–29 who received a human papillomavirus vaccine injection" which is not wrong, but very misleading because it leaves out the most important confounding factor: education.
@nytimes @gorskon What is completely scientifically incorrect is to use this paper to state that the HPV vaccine causes infertility.
It does not.
@nytimes @gorskon Update: I wrote a @PubPeer post with my concerns about this paper and invite others to chime in.
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