In 2015, the Danish television station TV2 sent a documentary called 'The vaccinated girls', in which a number of girls and women described symptoms such as fatigue, dizziness, headaches, difficulty concentrating, nausea and pain, that they experienced after receiving the HPV vaccine. The uptake of the vaccine subsequently fell drastically.

Since then, numerous research results have confirmed that the vaccine is both safe and effective, although without finding an explanation for the possible side effects. A new research result from Aarhus University now shows that several of the girls and women who were referred to a HPV centre due to possible side effects, had an infection such as e.g. a sore throat or sinusitis shortly before or shortly after their vaccination.

"In some of the cases, the infection may have been a triggering or contributory cause of the symptoms that led to a number of referrals to the HPV centres," explains Lene Wulff Krogsgaard, who is behind the study which formed part of her PhD dissertation at Aarhus University.

The results have been published in Plos Medicine.

The researchers have studied all infections treated either at the hospital, with prescriptions for medicine against infections, and/or by a general practitioner taking a throat swab to test whether a patient has a bacterial throat infection.

Side effects vary widely

"We find the strongest association between possible side effects and infections that have required treatment," says Lene Wulff Krogsgaard, and emphasises that the possible side effects among girls and women vary widely and do not lead directly to a diagnosis:

"There are side effects such as headaches, unexplained fatigue, abdominal pain, nausea, general malaise, fainting, etc. Many of the symptoms are similar to those that also characterise chronic fatigue syndrome. And as the infections have previously been linked to chronic fatigue syndrome, it gave us the idea of investigating the correlation between infections and possible side effects following the vaccine," explains the researcher.

 
The study included all HPV-vaccinated girls and women born between 1974 and 2006, who were vaccinated between 2006 and 2017. Of 600,400 girls and women, 1,755 were referred to an HPV centre with possible side effects. Of these 1,755, a total of 250 had contacted a medical doctor due to an infection, either in the month prior to or the month after the first vaccination, and of these, approximately 200 had an infection that required treatment.

"Our results are one piece in the jigsaw puzzle that will help us find an explanation as to why some girls and women experienced possible side effects after receiving the vaccine. Of course this is of interest for these patients, as many of them are looking for answers," says Lene Wulff Krogsgaard, who emphasises that follow ups are needed before final conclusions can be drawn. Mainly because this is the first time that the association between infections and possible side effects has been investigated.

"We need to confirm these findings, also to clarify whether infections alone or in combination with the HPV vaccine could have caused the symptoms that have been reported," she says.

Background for the results

• The study is a register-based study.
• The scientific article has been published in PLoS Medicine.
• The study is financed by the Danish Cancer Society and the Danish Health Foundation.
  

  Contact

Lene Wulff Krogsgaard
Statens Serum Institut
lewk@ssi.dk
M: 3268 5184

Dorte Rytter
Aarhus University, Department of Public Health
dr@ph.au.dk
M: 6038 1298