Socioeconomic inequalities in human papillomavirus knowledge and vaccine uptake: evidence from a cross-sectional study in China

Objective

Providing the human papillomavirus (HPV) vaccine is effective to eliminate the disparity in HPV-related cancers. It is unknown regarding inequality in the distribution of HPV vaccination in China since the vaccine was licensed and approved for use in 2016. This study aimed to examine socioeconomic inequalities in HPV-related knowledge and vaccination and identified factors associated with such inequalities.

Methods

Self-administered questionnaires measuring HPV-related knowledge and vaccine uptake were completed by 1,306 women through online survey platform. HPV knowledge was assessed using a 12-item question stem that covered the hazards of HPV infection, HPV vaccine dosage, benefits, and protection. Cluster analysis by combining monthly household income, educational level, and employment status was used to identify socioeconomic status (SES) class. The concentration index (CI) was employed as a measure of socioeconomic inequalities in HPV-related knowledge and vaccination. Linear regression and logistic regression were established to decompose the contributions of associated factors to the observed inequalities.

Results

The CI for HPV-related knowledge and vaccine uptake was 0.0442 and 0.1485, respectively, indicating the higher knowledge and vaccination rate were concentrated in groups with high SES. Education and household income made the largest contribution to these inequalities. Age, residency and cervical cancer screening were also important contributors of observed inequalities.

Conclusion

Socioeconomic inequalities in HPV-related knowledge and vaccination uptake are evident in China. Interventions to diffuse HPV-related information for disadvantaged groups are helpful to reduce these inequalities. Providing low or no-cost HPV vaccination and ensuring accessibility of vaccines in rural areas are also considered to be beneficial.

Infections in temporal proximity to HPV vaccination and adverse effects following vaccination in Denmark: A nationwide register-based cohort study and case-crossover analysis

BACKGROUND

Public trust in the human papilloma virus (HPV) vaccination programme has been challenged by reports of potential severe adverse effects. The reported adverse symptoms were heterogeneous and overlapping with those characterised as chronic fatigue syndrome (CFS) and have been described as CFS-like symptoms. Evidence suggests that CFS is often precipitated by an infection. The aim of the study was to examine if an infection in temporal proximity to HPV vaccination is a risk factor for suspected adverse effects following HPV vaccination.

METHODS AND FINDINGS

The study was a nationwide register-based cohort study and case-crossover analysis. The study population consisted of all HPV vaccinated females living in Denmark, born between 1974 and 2006, and vaccinated between January 1, 2006 and December 31, 2017. The exposure was any infection in the period ± 1 month around time of first HPV vaccination and was defined as (1) hospital-treated infection; (2) redemption of anti-infective medication; or (3) having a rapid streptococcal test done at the general practitioner. The outcome was referral to a specialised hospital setting (5 national HPV centres opened June 1, 2015) due to suspected adverse effects following HPV vaccination. Multivariable logistic regression was used to estimate the association between infection and later HPV centre referral. The participants were 600,400 HPV-vaccinated females aged 11 to 44 years. Of these, 48,361 (9.7%) females had a hospital-treated infection, redeemed anti-infective medication, or had a rapid streptococcal test ± 1 month around time of first HPV vaccination. A total of 1,755 (0.3%) females were referred to an HPV centre. Having a hospital-treated infection in temporal proximity to vaccination was associated with significantly elevated risk of later referral to an HPV centre (odds ratio (OR) 2.75, 95% confidence interval (CI) 1.72 to 4.40; P < 0.001). Increased risk was also observed among females who redeemed anti-infective medication (OR 1.56, 95% CI 1.33 to 1.83; P < 0.001) or had a rapid streptococcal test (OR 1.45, 95% CI 1.10 to 1.93; P = 0.010). Results from a case-crossover analysis, which was performed to adjust for potential unmeasured confounding, supported the findings. A key limitation of the study is that the HPV centres did not open until June 1, 2015, which may have led to an underestimation of the risk of suspected adverse effects, but stratified analyses by year of vaccination yielded similar results.

CONCLUSIONS

Treated infection in temporal proximity to HPV vaccination is associated with increased risk for later referral with suspected adverse vaccine effects. Thus, the infection could potentially be a trigger of the CFS-like symptoms in a subset of the referred females. To our knowledge, the study is the first to investigate the role of infection in the development of suspected adverse effects after HPV vaccination and replication of these findings are needed in other studies.

General Practitioner Attendance in Proximity to HPV Vaccination: A Nationwide, Register-Based, Matched Case-Control Study

Aim

This study aimed to describe and compare general practitioner (GP) attendance patterns in the years surrounding HPV-vaccination among cases suspected to experience adverse events and their matched controls in order to determine if a potential larger change in GP attendance among cases was observed in temporal relation to vaccination.

Methods

Register-based, matched case-control study. Cases were defined as women referred to specialized hospital settings (HPV-centers) for suspected adverse event between June 1st 2015 and December 31st 2015 (n=1458). Information on referral was obtained from the HPV-centers directly. Each case was matched with five controls on age at vaccination, region, time of first vaccine registration and total number of doses, resulting in a total study population of 8670 girls and women. Negative binomial regression analyses were used (i) to estimate mean yearly GP contacts among cases and controls, and (ii) to further investigate the relative difference in change in GP attendance following vaccination between cases and controls.

Results

Overall, cases displayed higher GP attendance than controls from five years before vaccination up until five years after. Compared to controls, cases increased their GP attendance more in the years following HPV vaccination, corresponding to a 40% increase in the incidence rate ratios (IRR) from before to after vaccination (ratio-IRR = 1.40 [1.36; 1.44]). The change occurred in close proximity to vaccination, and the pattern was the same independently of the year of vaccination. However, for the later vaccination years cases displayed an additional increase in their GP attendance around time of extensive media attention.

Conclusion

Girls and women being referred for suspected adverse events after HPV-vaccination changed their GP attendance pattern in close proximity to their first HPV-vaccination and not solely in temporal linkage to the onset of public debate.

On the contextual nature of vaccine safety monitoring: Adverse events reporting after HPV-vaccination in Denmark, 2015

BACKGROUND

In 2013-15, Denmark experienced an increase in reported suspected adverse events following vaccination (AEFI) against human papilloma virus (HPV). Dedicated centres ("One Access") were established in order to standardize management of patients who experienced medically unexplained physical symptoms after HPV vaccination. Since One Access was targeted patients with suspected AEFI after HPV vaccination, we used this opportunity to estimate completeness in AEFI reporting to the Danish Medicines Agency (DMA), and explore the topic of AEFI reporting from the perspective of physicians working at the centres to better understand health professionals' reporting behaviour.

METHODS

The study consisted of a quantitative and a qualitative part. In the quantitative analysis, we used the Danish civil registry number to merge a line-list of all One Access patients referred in 2015 with total number of patients who had reported suspected serious AEFI following HPV vaccination to the DMA in the years 2009-2015. We conducted four semi-structured interviews with doctors representing three out of five regions. The Theoretical Domains Framework together with empirical data from two clinical fieldtrips guided the formation of the qualitative study.

RESULTS

Among 1577 One Access patients, only 404 (26%) were reported to the DMA. We found significant regional differences in reporting completeness (p < 0.001) and differences between regions when looking at reporters' backgrounds (healthcare professionals vs non-professionals; p = 0.004). We identified several factors of importance for reporting behaviour amongst physicians, mainly under the domains of Knowledge, Motivation & Goals, and Environmental Context.

CONCLUSIONS

Despite an official aim of homogenous case management, reporting of suspected AEFI was incomplete with large regional differences. The qualitative study corroborated that reporting behaviour was contextual. This observation represents an important caveat in interpreting data from AEFI reporting, in particular when these data are used for research or policymaking.

Hospital contacts and diagnoses five years prior to HPV vaccination among females referred for suspected adverse vaccine effects: A Danish nationwide case-control study

BACKGROUND

High health care utilization before Human Papilloma Virus (HPV) vaccination might be associated with increased risk of suspected adverse effects (AE's) after vaccination. We investigated the association between hospital contacts and diagnoses before HPV vaccination and risk of later referral to a specialized hospital setting (HPV center) for suspected AE's.

METHODS

The study was a Danish register-based matched case-control study. Cases were females referred to an HPV center. Five controls per case were randomly selected in the source population of HPV vaccinated females. Information on hospital contacts and diagnoses was obtained from the Danish National Patient Registry. Conditional logistic regression analyses were used to investigate the association between having one or more diagnoses in each specific International Classification of Diseases 10th version (ICD-10) chapter five years before the HPV vaccination and subsequent referral to an HPV center.

RESULTS

We identified 1496 cases and 7480 controls. In total, 80% of the cases versus 65% of the controls had at least one hospital contact prior to HPV vaccination (Prevalence Proportion Ratio - PPR: 1.24 (95% Confidence Interval - CI: 1.21-1.27)), with 24% vs 12% (PPR: 1.97 (95% CI: 1.76-2.19)) having six or more contacts. Cases were more likely to have had a diagnosis in 15 out of 19 ICD-10 chapters before the vaccination, with ORs larger than 1.8 for infectious diseases, psychiatric diseases, diseases of the nervous, circulatory, digestive and musculoskeletal system, unspecific symptoms and unspecific contacts.

CONCLUSION

Pre-vaccination morbidity and health care utilization seem to play a role in the path leading to suspected AE's after HPV vaccination. Since many of the diagnoses that were particularly increased before vaccination in referred females are overlapping with the most frequent symptoms reported, we cannot exclude that for some of the females, the suspected AE's might have been existing already before the vaccination.