One-third of side effects felt by patients who received a vaccine against cervical cancer are believed to be caused by a dysfunction within the central nervous system, a study suggests.
“There is a possibility that a change is taking place inside the brain,” said Kusuki Nishioka, who heads Tokyo Medical University’s Institute of Medical Science and led researchers in an independent study.
Nishioka said it remains unclear whether the vaccination is directly responsible for the side effects, although many women developed a number of symptoms after receiving the vaccination, which is given to bolster the body's immune system.
One patient experienced 62 different side effects after receiving the vaccination, the most reported, including those related to the central nervous system.
The findings by Nishioka and six other medical experts were announced at a news conference in Nagano on Sept. 13.
The group studied the cases of about 2,500 women who complained about health problems after receiving a cervical cancer vaccine.
The researchers said they confirmed a total of 7,676 cases of side effects.
Of these, 2,570 cases, or 33 percent of the total, represented more than 80 kinds of side effects stemming from a dysfunction of the central nervous system.
They included forgetfulness, fainting, spasms, numbness and weakness.
The number of cases in which women complained about a sensory organ dysfunction, such as a narrowing of their visual field, came to 694. The figure for chronic pain in a large part of the body was 662.
Other members of the study group included Shunpei Yokota, doctor of pediatrics who heads the International University of Health and Welfare’s Atami Hospital, and specialists from the Jikei University School of Medicine and Juntendo University.
The group’s findings came after a panel of experts with the health ministry ruled out the possibility in January that a range of reported problems after receiving the vaccination were caused by changes within the immune system or central nervous system.
The panel also said there are no grounds for suspicions that problems which developed at least a month after receiving the vaccine are linked to the vaccination.
Of the 2,500 patients, the ministry plans to set up a system to treat 176 who complained about a wide range of symptoms centering on widespread pain and mobility disorders.
The ministry also plans to expand the treatment to other patients.
It stopped recommending the vaccination in June 2013 following a spate of reports about prolonged pain and other complaints.