By Brenda Baletti, Ph.D.

The prestigious Cochrane Library in November 2025 published two reviews touting the safety and efficacy of the HPV vaccine.

In a press release, Cochrane claimed the reports showed that girls vaccinated before age 16 were 80% less likely to develop cervical cancer, and that there was no evidence the human papillomavirus (HPV) vaccine caused any serious adverse events.

Cochrane is widely cited as the “gold standard” of systematic reviews. Major news organizations, from NBC News to The BMJ, repeated claims made in the press release.

The BMJ wrote that the researchers wanted to “share high quality data to counter misinformation spread on social media, which has had a massive impact on vaccination rates.”

The two reviews were published together. One assessed evidence from clinical trials, the other examined observational studies.

Co-author Nicholas Henschke declared that based on the reviews, “We now have clear and consistent evidence from around the world that HPV vaccination prevents cervical cancer.”

Co-author Hanna Bergman told Cochrane that the evidence from the clinical trials confirmed that HPV vaccines are “highly effective” and “without any sign of serious safety concerns.”

However, experts who analyzed the reviews in detail told The Defender that based on their analyses of the reviews, they determined that the authors relied on a small number of studies with a high risk of bias for their claim that the HPV vaccine prevented cancer.

The experts said they identified similar patterns when they analyzed other outcomes cited by the researchers.

“We know that the meta-analysis can only be as good as the quality of the studies included in the meta-analysis,” Lucija Tomljenovic, Ph.D., a biochemist, said.

Yet the vast majority of the studies the authors relied on to make their most dramatic conclusions about cancer and cancer-related lesions were at “serious or critical risk of bias,” according to the study authors themselves, she said.

“If this is not a gross misinterpretation of evidence, I don’t know what is,” Tomljenovic said.

A systematic review is a “study of studies,” a high-level research method that reviews, synthesizes and critically appraises the available body of evidence for a given disease or health topic in a standardized and systematic way.

Healthcare policymakers often use them to guide their decision-making.

Researchers use a crucial metric — “risk of bias” — to evaluate the studies and determine whether to include them in a systematic review.

Risk of bias indicates the likelihood that a study contains a systematic error that could cause its results to deviate from the truth, which could lead to an over- or underestimation of the effect of an intervention — in this case, the HPV vaccine.

Authors draw ‘completely misleading’ conclusions based on the evidence with high risk of bias

Although the two Cochrane reviews claimed to find an 80% reduction in cancer rates, the review of clinical trials stated that the studies evaluated “were not of sufficient duration for cancers to develop. Four studies reported on cancer. No cancers were detected.”

The observational review, which evaluated different studies to assess the impact of HPV vaccination on the general population, claimed there was “moderate‐certainty evidence” from 20 studies that HPV vaccination reduces the incidence of cervical cancer.

However, Tomljenovic said that only four of the 20 studies had a moderate risk of bias. The other 16 studies had either serious or critical risk of bias.

Of the four studies with a moderate risk of bias, one did not even include cervical cancer as an endpoint, and the follow-up was only seven years — which is not enough time for cancer to develop. Instead, the studies measured persistent HPV infections, Tomljenovic said.

As a proxy for cancer, many studies examined precancer outcomes, focusing on the reduction in CIN3+ — or cervical squamous intraepithelial neoplasia 3 — which are abnormal cells found on the cervix that may be precancerous and are caused by a high-risk HPV type.

Tomljenovic also found that of the 23 eligible studies included in the meta-analysis investigating CIN3+ lesions, only a single study was overall at moderate risk of bias. The other 22 had serious or critical risk of bias.

On this shaky basis, she said, the authors concluded, “There are now long-term outcome data from different countries and from different study designs that consistently report a reduction in the development of high-grade CIN and cervical cancer in females vaccinated against HPV in early adolescence.”

Tomljenovic called that conclusion “completely misleading.” She said that the authors of the Cochrane reviews themselves judged the vast majority of studies that “consistently” report reduction in cervical cancer and high-grade CIN lesions to be at serious and critical risk of bias.

“The best evidence for reduction from only a handful of studies was at a moderate risk of bias rather than low,” she added.

Lancet study conclusions, cited by Cochrane, are ‘patently absurd’

The Cochrane review of observational studies included the widely cited 2021 study in The Lancet, which investigated the impact of HPV vaccination in England. The Lancet study claimed to offer first direct evidence of prevention of cervical cancer using the Cervarix vaccine — not available in the U.S.

The Lancet study claimed an 87-97% relative reduction in cervical cancer rates and CIN3 lesions in girls vaccinated at ages 12-13 compared to unvaccinated girls.

The authors claimed that vaccination “has almost eliminated cervical cancer and cervical precancer up to age 25,” Tomljenovic said. However, her own analysis of U.K. cervical cancer statistics from Cancer Research UK tells a different story.

Tomljenovic found that data show that since the early 1990s, cervical cancer incidence rates decreased by 25% in females in the U.K., and have remained stable over the last decade.

She found that cervical cancer incidence rates reached their lowest point somewhere between 2004 and 2007 — a year before the HPV vaccine was introduced in the U.K.

“Since then, the incidence rates of cervical cancer have actually slightly increased, not decreased,” Tomljenovic said. “Therefore, these data completely contradict the conclusions of The Lancet study.”

In light of the cervical cancer incidence in the U.K. over time, she said, the claim by the The Lancet study authors that HPV vaccination with high coverage in 12-13-year-old girls has almost eliminated cervical cancer and cervical precancer up to age 25 “is patently absurd.”

Screening, healthy practices prevent cervical cancer, and affect study outcomes

Children’s Health Defense Senior Research Scientist Karl Jablonowski said, “The HPV vaccines are pushed, because they allegedly prevent cancer. Yet, a comprehensive review of the world’s literature on HPV vaccinations concludes an insufficient body of evidence exists.”

Dr. Sin Hang Lee, a pathologist and expert in molecular diagnostics who has extensively studied the HPV vaccine, told The Defender that most HPV infections — even high-risk types — are cleared by the immune system. He said cervical cancer is a predictable and preventable disease because it can be identified early through regular pap screenings and treated.

“With proper gynecological care, no woman should have cervical cancer or die of cervical cancer,” Lee said.

According to Lee, the cohort studies assessed in the Cochrane review that reported a reduced risk of cervical cancer following the HPV vaccine were conducted in countries where it is less likely that gynecologists may remind patients to do pap screening follow-ups.

The basic flaw of using observational cohorts to detect efficacy, he said, is that “observational studies are subject to healthy user effect and healthy adherer effect, which may lead to erroneous conclusions,” and create a statistical bias.

That means women who choose to receive a vaccine to prevent cervical cancer are also more likely to seek other preventive services and practice healthy behaviors that affect cervical cancer. This includes exercising more, eating a healthier diet, having fewer sex partners, and avoiding tobacco, excessive alcohol intake and illicit drugs.

“A healthy lifestyle is known to affect the rate of clearance of HPV infections,” Lee added.

Observational studies typically compare these women to women who did not get the vaccine, “which may lead to erroneous conclusions.”

No serious adverse effects?

The Cochrane authors also claimed their findings dispute claims about serious adverse effects “reported on social media.”

However, social media isn’t the only place where serious adverse events, including autoimmune conditions like POTS [postural orthostatic tachycardia syndrome] and POI [primary ovarian insufficiency], have been reported.

The vaccine adverse event databases (VAERS and VigiBase) contain reports of serious adverse events. So do numerous case studies and Merck’s own internal data — as revealed in court documents from hundreds of lawsuits filed in state and federal courts against Merck, the maker of the Gardasil HPV vaccine.

Writing in response to the Cochrane findings in a letter to The BMJ, Dr. Peter Gøtzsche, ousted founder of the Cochrane Collaboration and founder of the Institute for Scientific Freedom, wrote that his own research group conducted a peer-reviewed systematic review that found “the HPV vaccines increased serious nervous system disorders significantly.”

Gøtzsche said that as an expert witness in a case against Merck, he documented that Merck “had hidden cases of serious neurological harms on Gardasil from the drug regulators.” Gøtzsche published his findings in a recent book.

Other research studies have identified similar adverse events. This includes a study published in Human Vaccines and Immunotherapeutics in July 2025. The study, which analyzed reports in the VAERS database related to Gardasil between 2015 and 2024, used multiple statistical signal-detection methods to identify safety signals for the Gardasil vaccine.

The researchers identified signals for certain neurological and autoimmune-related conditions, including POTS, eye movement disorders, autoimmune thyroiditis and posture abnormality — none of which are isted on the vaccine’s label.

U.S. regulators taking a closer look at HPV vaccines?

When the Centers for Disease Control and Prevention (CDC) earlier this month reduced the number of recommended routine childhood vaccines, the agency left the controversial HPV vaccine on the schedule.

However, the CDC now advises a single dose of the HPV vaccine, instead of the previous two-dose regimen. In making the new recommendations, the U.S. Department of Health and Human Services cited a growing global consensus that one shot is effective at protecting against HPV.

Investigative reporter Maryanne Demasi, Ph.D., reported last week that after nearly two decades on the childhood immunization schedule, the HPV vaccine is being subjected to closer scrutiny.

The CDC’s Advisory Committee on Immunization Practices (ACIP) convened a new workgroup to reexamine the vaccine from the ground up — including its effectiveness, dosing, safety and long-term population impact.

Massachusetts Institute of Technology Professor Retsef Levi, a current ACIP member who has repeatedly called for longer safety follow-up and greater transparency about uncertainty in vaccine science, is leading the workgroup, Desmasi wrote.

Related articles in The Defender 

• Plaintiffs Will Appeal Ruling in Merck Gardasil Vaccine Injury Case
• Cervical Cancer ‘Nearly 100% Preventable’ With Regular Screenings — But Media Push Vaccines
• Cervical Cancer ‘Nearly 100% Preventable’ With Regular Screenings — But Media Push Vaccines
• CDC Relied on Cherry-picked Data to Claim No Link Between Merck’s Gardasil Vaccine and POTS

The post ‘Completely Misleading’: Scientists Accuse Cochrane Reviews of Using Biased Studies to Claim HPV Vaccine Prevents Cancer appeared first on Children’s Health Defense.

 

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