Study Weighs Risks of Vaccine for Cervical Cancer
By RONI CARYN RABIN
Published: August 18, 2009
The new vaccine designed to protect girls and young women from cervical cancer has a safety record that appears to be in line with that of other vaccines, a government report has found. Some serious complications occurred, including at least 20 deaths and two cases of Lou Gehrig’s disease, but they were not necessarily caused by the vaccine, the study said.
The most common serious complications after vaccination with Gardasil were fainting episodes and an increased risk for potentially fatal blood clots, possibly related to oral contraceptive use and obesity, the study found.
The vaccine has been given to more than seven million girls and young women nationwide and there is no way to prove that complications came from the vaccine.
But while the tone of the study, published in The Journal of the American Medical Association, was reassuring, the authors noted that the analysis was based on imperfect data drawn from reports made to a voluntary government surveillance database. The majority of adverse event reports were filed by Merck & Company, the vaccine’s manufacturer, and most failed to provide enough information for further investigation.
“We feel confident recommending people get the vaccine; the benefits still outweigh the risks,” said Dr. Barbara A. Slade, the study’s first author and medical officer with the Centers for Disease Control and Prevention, which did the study together with the Food and Drug Administration. She added, “This is the most complete picture we have.”
Nevertheless, an accompanying editorial questioned whether any level of risk is acceptable when inoculating a healthy population against a disease that can be prevented through screening.
“There are not a huge number of side effects here, that’s fairly certain,” said the editorial writer, Dr. Charlotte Haug, an infectious disease expert from Norway, about the vaccine. “But you are giving this to perfectly healthy young girls, so even a rare thing may be too much of a risk.
“I wouldn’t accept much risk of side effects at all in an 11-year-old girl, because if she gets screened when she’s older, she’ll never get cervical cancer,” Dr. Haug said in an interview. “You don’t have to die from cervical cancer if you have access to health care.”
The vaccine was approved for girls and young women ages 9 to 26 and is recommended for routine vaccination of girls 11 and 12.
Merck officials said they were pleased with the findings of the new report.
“This confirms the very favorable safety profile we’ve seen in our extensive clinical trials,” said Dr. Richard M. Haupt, executive director of clinical research for Merck Research Laboratories, adding that while screening is important, the vaccine can reduce the number of abnormal results and procedures, because it prevents infection with four strains of HPV, including two implicated in most cases of cervical cancer today.
“Pap screening alone is not the answer,” Dr. Haupt said.
Another paper in JAMA described how Merck, whose sales of Gardasil totaled $1.4 billion last year, provided professional medical societies with grant money the organizations used to develop educational programs promoting the product. The lectures glossed over questions about the vaccine’s effectiveness and whether booster shots would be needed, said Sheila M. Rothman, the paper’s author.
“The message they were giving was really the drug company message,” said Dr. Rothman, professor of sociomedical sciences at Mailman School of Public Health at Columbia. The marketing strategy overstated the risks of cervical cancer for American women, she said. “It was being marketed as if every girl were at equal risk for this disease and needed this vaccine, even though cervical cancer is not a disease of all women in the U.S. — it particularly affects girls who don’t have access to health care and Pap tests,” Dr. Rothman said.
The study on adverse events analyzed 12,424 reports of adverse events that occurred after immunization with the HPV vaccine from June 1, 2006, to Dec. 31, 2008, when more than 23 million doses of vaccine were distributed, enough to vaccinate more than seven million girls with all three required doses.
That was calculated as a rate of 53.9 adverse event reports to the Vaccine Adverse Event Reporting System for every 100,000 doses of vaccine distributed. Syncope, or fainting, occurred most frequently, with a rate of 8.2 reports per 100,000 vaccine doses, followed by 7.5 per 100,000 for local site reactions and 6.8 per 100,000 for dizziness.
Report rates were then compared with those of other vaccines given in similar populations of girls the same age, Dr. Slade explained.
Of the total number of reports, 6.2 percent, or 772 reports, were considered serious events, including 32 reports of death. Only 20 of the deaths could be verified; the others included four that were provided by the manufacturer without further information, and eight secondhand reports that could not be verified.
Of the 20, 14 of the deceased had only received the HPV vaccine, while others had received multiple vaccines. The average age of the girls who died was 18, and causes of death varied widely — including two cases of diabetic ketoacidosis, one case related to prescription drug abuse, one case of juvenile amyotrophic lateral sclerosis or Lou Gehrig’s disease, one case of meningoencephalitis, three pulmonary embolisms or blood clots to the lung, six cardiac-related deaths, one case of sepsis related to influenza B and two because of seizure disorders. Four deaths were unexplained.
Dr. Slade said the disparate causes of death made it difficult to determine an underlying cause, or to determine if the vaccine played a causal role.
“We didn’t see any patterns in the causes of death, any pattern in the time between vaccination and death, or the age of the people who died — there just didn’t seem to be any real pattern that would cause us to have heightened concern,” Dr. Slade said, adding that the number of deaths was “actually very similar to what we see after other vaccines in similar age groups.” She said the A.L.S. cases were being investigated further.
The American Cancer Society provides the following list of risk factors for cervical cancer: human papillomavirus (HPV) infection, smoking, HIV infection, chlamydia infection, dietary factors, hormonal contraception, multiple pregnancies, exposure to the hormonal drug diethylstilbestrol (DES) and a family history of cervical cancer. There is a possible genetic risk associated with HLA-B7.
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