A May 2018 Cochrane HPV vaccine review was supposed to put vaccine safety and effectiveness concerns to rest. Instead, critics questioned the integrity of the review process.
Many Americans still have questions about rare HPV vaccine side effects such as Guillain-Barre Syndrome and fainting. And HPV vaccination rates, which could reduce the annual 30,000 cases of HPV-related cancers in the United States if increased, remain lower than health officials would like.
For example, only about 66 percent of adolescents aged 13 to 17 received the vaccine in 2017, and more than half of that 66 percent never completed the series of shots, according to the CDC.
The Centers for Disease Control and Prevention has been pushing to get those vaccination rates up and address safety concerns.
The Cochrane review was important because it gave the green light to parents, doctors and patients. It found the vaccine was effective and without “an increased risk of serious adverse effects.”
But two months after Cochrane published the review, a trio of researchers from the Nordic Cochrane Centre in Copenhagen claimed the review was incomplete and biased.
“Cochrane has high standards for its reviews. However, there were important limitations in its HPV vaccine review,” said researchers Lars Jørgensen, Peter Gøtzsche and Tom Jefferson.
Let’s explore some of the criticisms of Cochrane’s review.
One of the key criticisms of the review is that it left out relevant clinical trials.
In fact, Cochrane left out nearly half of the trials and half of the participants in its review, the researchers said.
In January 2018, Jørgensen, Gøtzsche and Jefferson published an index of 206 industry clinical studies and nonindustry studies in the journal Systematic Reviews. According to the researchers, 46 of those 206 trials were complete and eligible for inclusion in the Cochrane review.
Yet Cochrane included only 26 in its review. They left out 20 eligible trials and about 48,000 women from the review.
While Cochrane claimed that the studies compared the HPV vaccine with placebos (harmless substances with no therapeutic effects), according to the researchers, all the included trials compared the HPV vaccine with active substances, such as hepatitis vaccines, that may have “masked harms caused by the HPV vaccines.”
Cochrane should have noted this in its review.
In response, Cochrane announced it is conducting an investigation into the review process.
“We fully understand the severity and importance of the criticisms made, whose implications go well beyond this review in terms of systematic review methodology,” editor-in-chief of the Cochrane Library David Tovey told BMJ. “For this reason, we have had a team of editors working with the author team to investigate the claims as a matter of urgency.”
The Cochrane team had received the list of potentially eligible trials, but “at the time it did not appear to identify any important eligible studies.”
It disputes that it left out half the studies and data.
“Our current investigations appear to show that there may be a handful of missed but potentially eligible studies, but that this falls substantially below ‘nearly half of the eligible trials,’” Tovey said.
While it intends to update the review, Cochrane says this does not change the review’s conclusion about the risks and benefits of the vaccine.
Drugwatch Tip: Always take the time to carefully read studies and their criticisms. This study intentionally ignored nearly half of the trials and half of the participants that should have been included. This is an example of how studies and reviews may be biased.
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