Eighteen months ago, a paper claiming to demonstrate neurological damage in mice caused by the human papillomavirus (HPV) vaccine was published by a Japanese team in the journal Scientific Reports.

Now the paper has been retracted against the authors’ wishes, but the vaccination rate in Japan has already plummeted.

The retraction notice was issued by the journal on Friday, 18 months after the paper was published online in November 2016.

“The study was designed to elucidate the maximum implication of human papilloma virus (HPV) vaccine (Gardasil) in the central nervous system,” the journal writes in the notice. “However, the co-administration of pertussis toxin with high levels of HPV vaccine is not an appropriate approach to determine neurological damage from HPV vaccine alone.

“The authors do not agree with the retraction,” the note adds.

The 48 mice were split into groups: some were given high doses and others were not. But all were administered pertussis toxin to break down the natural blood-brain barrier, the scientists outlined in their study.

The mice who had the HPV vaccine and the toxin developed poor tail movement and low mobility, according to the results. Within the mice, they reported structural damage to the neurological system, and increased apoptosis around the thalamus and hypothalamus, among other effects.

Other studies around the world, however, have shown no such linkage.

For instance, a study of about 1 million girls in Denmark and Sweden found no statistical correlation between serious adverse events including neurological problems and the vaccine. Those findings were published in the BMJ in 2013. A paper published last week found that, overall, the HPV vaccines prevent deadly cervical cancer.

Japan has had stark opposition to the HPV vaccine. Women claiming adverse reactions were part of what led the national health ministry to stop recommending the vaccine in 2013 – even though the shots were freely available for years before that. With the latest skepticism from the 2016 paper, the overall Japanese vaccination rate among the target female age group has dropped from 70 percent to “near zero.”