Claims of new study concluding COVID vaccines do not affect fertility called into question: Analysis

Jan 09, 2022


12:16 PM

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By: David Heller

Recently a new study was published in the journal Human Reproduction that looked to see if there was a reduction in Anti Müllerian Hormone (AMH) in women who received the two-dose COVID Pfizer vaccine. The study concluded that the AMH levels measured before vaccination and three months after vaccination “did not change significantly”. This was reported in the press under the headline “COVID vaccine does not cause infertility”. Prof. Jaron Rabinovici, who co-authored the study, was quoted saying “This groundbreaking study shows that the vaccine does not affect a woman’s level of fertility.” 

Since the release of the new COVID vaccines, there were many concerns on how the new technology might affect fertility. Does this study alleviate these concerns? Prof Rabinovici seems to think so, “This study gives us for the first time a very objective measure and evidence about the lack of negative effects of the vaccines on ovarian function of fertility.” is what he said to the Jerusalem Post.

The study however has a number of issues that call the grandiose claims into question. AMH levels, which the study was measuring, are not even a direct indicator of current fertility. A study in JAMA explains that “diminished ovarian reserve was not associated with infertility; women should be cautioned against using AMH levels to assess their current fertility.” AMH decline can be an indicator of how soon a woman will reach menopause, but not a measure of their ability to conceive. Furthermore, Dr. Daniel Stock MD explains that AMH is produced by follicle granulosa cells, but only after they leave the primordial state. So, if you destroy egg cells and granulosa cells in the primordial state, then that damage won't be reflected at all by AMH.

It's important to know what the normal AMH decline is because the study did not compare vaccinated to unvaccinated women. Rather it measured the levels in the same women before and then after vaccination. The study acknowledges that a comparative study would be better, but claims it would be unethical to do so since it would limit some women from getting vaccinated. Though this could have been done by simply finding women who had no intention of getting vaccinated anyway. Then there would have been an actual comparison with the only variable being vaccination.

Assuming AMH levels were a valid indicator of fertility, and a comparative study would not be appropriate, how would one know if the decline in AMH is normal? The study used 10% as a “significant decrease” over the three-month period since vaccination. The study did not explain why they picked 10% as a “significant decrease” but did say that the decrease “reflects a well-known decrease in ovarian reserve that occurs with age (Broer et al. 2014)”. Broer et al 2014 states that the “average annual decline has been calculated to be 5.6%” and refers to this study as a source. Meaning that the expected normal AMH reduction would be just 1.4% in three months. It’s still unclear why the study did not use a 1.4% decrease as a measure of what’s normal as per Broer et al 2014. What’s more concerning is that the women who experienced a 10% reduction, had a reduction about seven times normal.    

Yaffa Shiraz, health and risk communication researcher and lecturer at Haifa University, points out that while the study states “No significant difference for the changes in AMH levels before and after vaccination (Delta AMH) were observed for any of the three groups.” The problem is that the study included a table (page 22) that shows a decrease of over 10% in between 32% - 42% of women (depending on the age range). If a 10% decline was significant, and it occurred in more than a third of the participants - how can the study conclude there is no significant decrease?   


So the study measured a hormone that does not reflect current fertility, did not compare based on vaccination status, sets a seemingly arbitrary and high 10% as a significant reduction, and still found about a third of the women experienced such a decline. The author then concludes that his study shows that “the [COVID] vaccine does not affect a woman’s level of fertility”. A conclusion that’s a stretch at best. After examining the study, Dr. Stock offers a more modest assessment saying, “This study shouldn't reassure anyone about the destruction of reproductive capacity among the vaccinated.”  

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