National surveillance of the HPV immunisation programme (project description)
The surveillance programme was established to monitor the vaccination coverage, effectiveness and safety of the HPV immunisation programme. It includes several research projects that will study the effectiveness of the programme on the incidence of HPV infection and HPV-related cancer as well as other aspects of the HPV immunisation programme.
The HPV vaccine has been offered to girls in the 7th grade as part of the childhood immunisation programme since the school year 2009/2010. During 2016-2018, HPV vaccine was also offered to women born in 1991 or later through a two-year catch-up programme.
From autumn 2018 boys have also been offered HPV vaccine during 7th grade through the childhood immunisation programme.
When a vaccine is introduced in the childhood immunisation programme, it is important to monitor the effectiveness of the vaccine on the incidence of the diseases in the population. The effectiveness of the HPV vaccine in women can be measured by studying changes in the incidence of cervical dysplasia and cervical cancer. Similarly, the effectiveness in men can be measured by studying changes in the incidence of HPV-related cancer in men over time. It may take several years from an infection with HPV occurs until cervical dysplasia or cervical cancer as well as other HPV-related cancers are developed. Surveillance of the HPV vaccine will therefore continue over many years.
What is being monitored?
1. Vaccination Coverage
In Norway, all vaccinations in the childhood immunisation programme are recorded in the national immunisation registry SYSVAK. Information about which vaccines are given, and the date of vaccination is recorded for each individual. Information about vaccines given and immunisation certificates are available to the individual from the online Vaccines (helsenorge.no).
This information is available also for health professionals. Data from SYSVAK are used to monitor the effectiveness and safety of the vaccines included in the programme. Individual information on HPV vaccination status is necessary when comparing the incidence of HPV infection, cervical dysplasia (pre-cancerous cellular changes in the cervix) and cervical cancer as well as possible adverse events among vaccinated and unvaccinated individuals. Registration in SYSVAK also provides an overview of the vaccination coverage at municipal, county and national levels.
2. Adverse events
All vaccines in the childhood immunisation programme are carefully monitored to identify possible adverse events. Serious and / or unexpected events are reported to the Norwegian Institute of Public Health and are reviewed in collaboration with the Norwegian Medicines Agency. Norway also participates in a European collaboration for surveillance of adverse events following vaccination and reports any unwanted and suspected side effects in Norway to the European network. In addition, studies are being performed to investigate whether there is a possible association between HPV vaccination and possible side effects. One study from the surveillance programme published in 2017 showed that girls who have received one or more doses of HPV vaccine have no increased risk of chronic fatigue syndrome (CFS / ME) compared to girls who have not received the vaccine (1).
3. Vaccine effectiveness
Vaccine effectiveness among women
The incidence of vaccine preventable diseases covered by the immunisation programme is routinely monitored to measure vaccine effectiveness in the population. In addition, vaccine effectiveness is being monitored through research projects. The effectiveness of the HPV vaccine can be measured by studying incidence of HPV infection, precursors of cervical cancer, cervical cancer and other HPV-related cancers. In addition, changes in the incidence of infection with different types of HPV are studied to see if the types the vaccine should protect against decrease among vaccinated women, and whether the vaccine leads to at decrease also in in other HPV types, so-called cross protection. The prevalence of HPV infection in vaccinated and unvaccinated girls and young women in Norway is being studied by testing for HPV in urine samples from different cohorts aged 17 and 21 years in repeated cross-sectional national studies. As of December 2022, about 65,000 young women have participated in the studies. The results show that the incidence of HPV in unvaccinated 17-year-olds in the cohorts that were not offered the vaccine is high and HPV was detected in 15-20 percent of the girls. In 21-year-olds, the incidence is even higher and about 45% tested positive for HPV in the urine sample (2). This shows that HPV infection is very common in young women. The HPV types that the vaccines used in the programme, protect against are commonly prevalent.
In a study from the surveillance program, results show that the first cohort who were offered HPV vaccine in the 7th grade (girls born in 1997) had a significantly lower incidence of HPV than girls in older cohorts who were not offered the vaccine. For the 1997 cohort as a whole, the incidence of all HPV types was reduced by a total of 42 percent, while the vaccine preventable types were reduced by 81 percent (3).
A study published in 2020 comparing girls who had not received the vaccine as part of the childhood immunisation programme with a group of vaccinated girls showed that infection with multiple types of HPV was more common among girls from the unvaccinated group (4).
Precursors of cervical cancer and cervical cancer are routinely reported to the Norwegian Cancer Registry (5). By compiling data from the Norwegian Cancer Registry and SYSVAK, the incidence of precursors of cervical cancer and cervical cancer among vaccinated and unvaccinated women is compared. In addition, the Cancer Registry reports precursors of cervical cancer and cervical cancers to the Norwegian Surveillance System for Communicable diseases (MSIS) (6). For a selection of women with precursors of cervical cancer and for all cases of cervical cancer, tissue samples are obtained from the different pathology laboratories for HPV analysis at the HPV reference laboratory at Akershus University Hospital. Positive HPV test results are recorded in the MSIS registry. Through the compilation of test results from MSIS and information on vaccination status from SYSVAK, the effect of HPV vaccination on the incidence and changes of HPV types in precursors of cervical cancer and cervical cancer is being monitored. HPV examination of tissue samples from women with precursors of cervical cancer or cervical cancer is allowed through the MSIS regulations. Women may reserve themselves against storing residual material after HPV testing (7). More information about MSIS-HPV and reservation:
- HPV i MSIS (Folkehelseinstituttet)
- Informasjon til kvinner med kreft eller forstadier til kreft i livmorhalsen (Folkehelseinstituttet)
Vaccine effectiveness among men
From the autumn of 2018, also boys have been offered the HPV vaccine through the childhood immunisation programme. The effectiveness of the HPV vaccine in men can be measured by studying changes in the incidence of HPV-related cancer in men over time. However, this can only be done after several years, because it normally takes many years from HPV infection to cancer develops. In order to measure the vaccine effectiveness in boys, young men are invited to participate in repeated cross-sectional national studies where urine samples from different cohorts are HPV tested, similar to the ongoing studies for young women. In the autumn of 2018, 10 000 young men (21 years) were invited to submit a urine sample. In 2019 and 2020, 15 000 young men (17 years) were invited, and in 2021, 15 000 (21 years) were invited.
Studies in 2023
In 2023, 15 000 young women born in 2006 (17 years) will be invited to participate to study long term effectiveness of the vaccine.
1) Feiring B, Laake I, Bakken IJ, Greve-Isdahl M, Bruun Wyller V, Håberg S, Magnus P,
Trogstad L. HPV vaccination and risk of chronic fatigue
syndrome/myalgic encephalomyelitis: A nationwide register-based study from
Norway. Vaccine 2017;35: 4203-4212.
2) Molden T, Feiring B, Ambur OH, Christiansen IK, Hansen M, Laake I, Meisal R, Myrvang E, Jonassen CM, Trogstad L. Human papillomavirus prevalence and type distribution in urine samples from Norwegian women aged 17 and 21 years: A nationwide cross-sectional study of three non-vaccinated birth cohorts. Papillomavirus Research, May (2016).
3) Feiring B, Laake I, Christiansen IK, Hansen M, Stålcrantz J, Ambur OH, Magnus P, Jonassen CM, Trogstad L. Substantial decline in prevalence of vaccine-type and non-vaccine type HPV in vaccinated and unvaccinated girls 5 years after implementing HPV vaccine in Norway. Journal of Infectious Diseases 2018; 16. July 2018.
4) Laake I, Feiring B, Jonassen VM, Pettersson JHO, Frengen TG, Kirkeleite IØ, Trogstad L: Concurrent Infection With Multiple Human Papillomavirus Types Among Unvaccinated and Vaccinated 17-Year-Old Norwegian Girls, The Journal of Infectious Diseases, 2020;, jiaa709, https://doi.org/10.1093/infdis/jiaa709