Impact of the quebec school-based hepatitis B immunization program and potential benefit of the addition of an infant immunization program

Characterization of Acute and Chronic Hepatitis B Virus Genotypes in Canada

Objective

The prevalence and distribution of hepatitis B virus (HBV) genotypes in Canada is not known. Genotypic analysis may contribute to a better understanding of HBV strain distribution and transmission risk.

Methods

HBV surface antigen (HBsAg) positive samples of acute (n = 152) and chronic (n = 1533) HBV submitted for strain analysis or reference genotype testing between 2006 and 2012 were analyzed. The HBsAg coding region was amplified to determine the HBV genotype by INNO-LiPA assay or sequence analysis. Single and multivariate analyses were used to describe genotypes’ associations with known demographic and behavioral risk factors for 126 linked cases of acute HBV.

Results

Nine genotypes were detected (A to I), including mixed infections. Genotype C (HBV/C) dominated within chronic infections while HBV/D and A prevailed among acute HBV cases. History of incarceration and residing with a chronic HBV carrier or injection drug user were the most frequently reported risks for acute HBV infection. Over time, HBV/A increased among both acute and chronic infections, and HBV/C and HBV/D decreased among chronic infections.

Conclusion

Chronic and acute HBV genotypes in Canada differ in the relative distribution and their associations with known risk factors, suggesting different routes of transmission and clinical progression of infection.

Dramatic reduction in hepatitis B through school-based immunization without a routine infant program in a low endemicity region

BACKGROUND

Hepatitis B (HB) prevention in the low-endemicity province of Quebec Canada, (population: ~8.2 million; birth cohort ~85,000/year), includes two decades of pre-adolescent school-based immunization, as well as catch-up immunization for those born since 1983 and pre-natal maternal HBsAg screening. To estimate the potential added benefit of routine infant HB immunization, notifiable disease reports were analyzed (1990-2013). Clinical and demographic information about cases was retrieved from standard questionnaires used by local public health units to investigate HB cases.

METHODS

The Quebec provincial registry of notifiable diseases was used to identify confirmed HB cases reported between 1990 and 2013. Clinical and demographic information on cases was retrieved from the standard questionnaires used by local public health units to investigate reported HB cases.

RESULTS

Between 1990-2013, acute-HB incidence per 100,000 population decreased by 97 % from 6.5 to 0.2. Compared to 1990, incidence fell from 0.6 to zero since 2010 among children ≤9 years of age (yoa), from 3.2 to zero since 2007 in those 10-19 yoa, and from 15 to zero in 2013 among adults 20-29 yoa, previously the age group of highest incidence (all p < 0.0001). During the same period, the newly-reported chronic HB rate per 100,000 decreased by 66 % from 17.7 to 6.1 (p < 0.0001), with a reduction of 92 % (2.4 to 0.2;p < 0.001) in children ≤9 yoa and 83 % (7.2 to 1.2;p = 0.003) in those 10-19 yoa. The incidence of unspecified HB cases did not decrease significantly overall (5.9 vs. 5.4; p = 0.24), in children ≤ 9 yoa (0.3 vs. 0.2;p = 0.70) or 10-19 yoa (1.6 vs. 1.5;p = 0.45). Overall, 91 % of cases ≤19 yoa were immigrants likely infected before arrival in Canada. Among those ≤9 yoa, there were 9 acute-HB case reports between 2005 and 2013, of whom 8 were not preventable by infant immunization.

CONCLUSIONS

Two decades of school-based immunization coupled with prenatal screening achieved striking reduction in disease burden in the low-endemicity province of Quebec, Canada. The oldest cohorts targeted by catch-up campaigns are now beyond the average age at childbirth so that neo-natal transmission and the potential incremental benefit of infant immunization will likely further diminish.

Parents' decision-making about the human papillomavirus vaccine for their daughters: I. Quantitative results

Vaccination against the human papillomavirus (HPV) is an effective primary prevention measure for HPV-related diseases. For children and young adolescents, the uptake of the vaccine is contingent on parental consent. This study sought to identify key differences between parents who obtain (acceptors) and parents who refuse (non-acceptors) the HPV vaccine for their daughters. In the context of a free, universal, school-based HPV vaccination program in Québec, 774 parents of 9-10 year-old girls completed and returned a questionnaire by mail. The questionnaire was based on the theoretical constructs of the Health Belief Model (HBM), along with constructs from other theoretical frameworks. Of the 774 parents, 88.2% reported their daughter having received the HPV vaccine. Perceived susceptibility of daughters to HPV infection, perceived benefits of the vaccine, perceived barriers (including safety of the vaccine), and cues to action significantly distinguished between parents whose daughters had received the HPV vaccine and those whose daughters had not. Other significant factors associated with daughter vaccine uptake were parents' general vaccination attitudes, anticipated regret, adherence to other routinely recommended vaccines, social norms, and positive media influence. The results of this study identify a number of important correlates related to parents' decisions to accept or refuse the HPV vaccine uptake for their daughters. Future work may benefit from targeting such factors and incorporating other health behavior theories in the design of effective HPV vaccine uptake interventions.

Interventions aimed at communities to inform and/or educate about early childhood vaccination

BACKGROUND

A range of strategies are used to communicate with parents, caregivers and communities regarding child vaccination in order to inform decisions and improve vaccination uptake. These strategies include interventions in which information is aimed at larger groups in the community, for instance at public meetings, through radio or through leaflets. This is one of two reviews on communication interventions for childhood vaccination. The companion review focuses on face-to-face interventions for informing or educating parents.

OBJECTIVES

To assess the effects of interventions aimed at communities to inform and/or educate people about vaccination in children six years and younger.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE and five other databases up to July 2012. We searched for grey literature in the Grey Literature Report and OpenGrey. We also contacted authors of included studies and experts in the field. There were no language, date or settings restrictions.

SELECTION CRITERIA

Individual or cluster-randomised and quasi-randomised controlled trials, interrupted time series (ITS) and repeated measures studies, and controlled before-and-after (CBA) studies. We included interventions aimed at communities and intended to inform and/or educate about vaccination in children six years and younger, conducted in any setting. We defined interventions aimed at communities as those directed at a geographic area, and/or interventions directed to groups of people who share at least one common social or cultural characteristic. Primary outcomes were: knowledge among participants of vaccines or vaccine-preventable diseases and of vaccine service delivery; child immunisation status; and unintended adverse effects. Secondary outcomes were: participants' attitudes towards vaccination; involvement in decision-making regarding vaccination; confidence in the decision made; and resource use or cost of intervention.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the references to identify studies for inclusion. We extracted data and assessed risk of bias in all included studies.

MAIN RESULTS

We included two cluster-randomised trials that compared interventions aimed at communities to routine immunisation practices. In one study from India, families, teachers, children and village leaders were encouraged to attend information meetings where they received information about childhood vaccination and could ask questions. In the second study from Pakistan, people who were considered to be trusted in the community were invited to meetings to discuss vaccine coverage rates in their community and the costs and benefits of childhood vaccination. They were asked to develop local action plans and to share the information they had been given and continue the discussions in their communities.The trials show low certainty evidence that interventions aimed at communities to inform and educate about childhood vaccination may improve knowledge of vaccines or vaccine-preventable diseases among intervention participants (adjusted mean difference 0.121, 95% confidence interval (CI) 0.055 to 0.189). These interventions probably increase the number of children who are vaccinated. The study from India showed that the intervention probably increased the number of children who received vaccinations (risk ratio (RR) 1.67, 95% CI 1.21 to 2.31; moderate certainty evidence). The study from Pakistan showed that there is probably an increase in the uptake of both measles (RR 1.63, 95% CI 1.03 to 2.58) and DPT (diptheria, pertussis and tetanus) (RR 2.17, 95% CI 1.43 to 3.29) vaccines (both moderate certainty evidence), but there may be little or no difference in the number of children who received polio vaccine (RR 1.01, 95% CI 0.97 to 1.05; low certainty evidence). There is also low certainty evidence that these interventions may change attitudes in favour of vaccination among parents with young children (adjusted mean difference 0.054, 95% CI 0.013 to 0.105), but they may make little or no difference to the involvement of mothers in decision-making regarding childhood vaccination (adjusted mean difference 0.043, 95% CI -0.009 to 0.097).The studies did not assess knowledge among participants of vaccine service delivery; participant confidence in the vaccination decision; intervention costs; or any unintended harms as a consequence of the intervention. We did not identify any studies that compared interventions aimed at communities to inform and/or educate with interventions directed to individual parents or caregivers, or studies that compared two interventions aimed at communities to inform and/or educate about childhood vaccination.

AUTHORS' CONCLUSIONS

This review provides limited evidence that interventions aimed at communities to inform and educate about early childhood vaccination may improve attitudes towards vaccination and probably increase vaccination uptake under some circumstances. However, some of these interventions may be resource intensive when implemented on a large scale and further rigorous evaluations are needed. These interventions may achieve most benefit when targeted to areas or groups that have low childhood vaccination rates.'

The next decade of vaccines: societal and scientific challenges

Vaccines against microbial diseases have improved the health of millions of people. In the next decade and beyond, many conceptual and technological scientific advances offer extraordinary opportunities to expand the portfolio of immunisations against viral and bacterial diseases and to pioneer the first vaccines against human parasitic and fungal diseases. Scientists in the public and private sectors are motivated as never before to bring about these innovations in immunisation. Many societal factors threaten to compromise realisation of the public health gains that immunisation can achieve in the next decade and beyond--understanding these factors is imperative. Vaccines are typically given to healthy individuals and safety issues loom high on the list of public concerns. The public needs to regain confidence in immunisation and trust the organisations responsible for the research, development, and implementation of vaccines. In the past, by use of a judicious amalgam of knowledge and empiricism, successful vaccines were largely developed by microbiologists who identified antigens that induced immune responses to conserved pathogen components. In the future, vaccines need to be developed against deadly diseases for which this strategy is often not feasible because of the extensive antigenic variability of relevant pathogens. High microbial diversity means that immunity after natural infection is often ineffective for prevention of disease on subsequent exposure, for example in HIV infection and malaria. Additionally, vaccines need to be generated to protect the people who are most vulnerable because of age or underlying diseases. Thus, in the future, a much deeper understanding of the immunological challenges--including the diversifying role of host genetics and environmental factors, leading perhaps to more personalised approaches-will be the touchstone for rational design and development of adjuvants that result in novel safe and effective vaccines.

Optimizing the acceptability, effectiveness and costs of immunization programs: the Quebec experience

In Canada, publicly funded immunization programs are a provincial/territorial responsibility. In the province of Quebec, much effort has been devoted to optimize the acceptability, effectiveness and cost-effectiveness of publicly funded immunization programs for children during the last 20 years. The aim of this article is to describe how programs are planned, implemented and evaluated and to identify key factors that contribute to the success of this enterprise. A comprehensive framework was developed for the evaluation of new vaccines and new programs in a societal perspective. It is used by the Quebec Immunization Committee to prepare reports proposing options with their costs and consequences for the public health authority. When a decision is made, the implementation of the new program is carefully planned. Surveys and consultations with stakeholders are systematically conducted to identify potential obstacles. A fraction of the budget is always reserved for program evaluation and monitoring. At the present time, the recommended immunization schedule targets 15 different diseases and only 20 injections are offered up to 15 years of age. Vaccine uptake rate is high and, although a reduced number of doses are recommended for several vaccines, program effectiveness is highly satisfactory, as shown for hepatitis B, meningococcal and pneumococcal diseases.

Long-term immunogenicity of two pediatric doses of combined hepatitis A and B or monovalent hepatitis B vaccine in 8 to 10-year-old children and the effect of a challenge dose given seven years later

A total of 465 children aged 8 to 10 years were vaccinated with 2 doses of Recombivax-HB 2.5 microg (RB) or Twinrix-Junior 10 microg/360 EL.U (TX), according to a 0 and 6 months schedule. Seven years postsecond dose, a challenge dose of vaccine was given. All vaccinees in the TX and 98% in the RB group showed an anamnestic response. Vaccination at the age of 8 to 10 years with two-pediatric doses of TX or RB given with a 6 months interval induces a long-lasting immunity in most vaccinees.

Antibody kinetics among 8-10 years old respondents to hepatitis B vaccination in a low endemic country and the effect of a booster dose given 5 or 10 years later

Few data are available concerning the persistence of anti-HBs and the effect of booster doses given several years post-vaccination against hepatitis B during preadolescence. The objective of this open-labelled clinical trial was to evaluate the persistence of antibodies after vaccination with three paediatric doses of Engerix-B at the age of 8-10 years and the effect of a booster dose given 5 (Group Y5) or 10 (Group Y10) years later. Anti-HBs were measured before and one month post-primary vaccination, then 5 and 10 years later, before the booster dose, as well as one month and 1 year post-booster. The anamnestic response was defined as a >or=fourfold increase of anti-HBs post-booster (>or=10 IU/L) when compared to pre-booster. Ten years post-primary vaccination, 559 of the 652 initially randomized subjects (86%) were eligible for analysis. Group Y5, 5 years post-booster results: 99% of subjects had detectable levels of antibodies and 96% a titer >or=10 IU/L. The anti-HBs GMTs decreased from 114,489 IU/L one month post-booster to 3354 IU/L 5 years later. Group Y10 results: 10 years post-primary vaccination 96% of subjects had a detectable level of anti-HBs and 85% were above the threshold of 10 IU/L. The GMTs one month post-booster were 31,030 IU/L. The challenge with a booster demonstrated an anamnestic response in 99% of subjects in group Y5 and 100% of subjects in group Y10. All subjects were anti-HBc negative. The booster doses were well tolerated. The excellent anamnestic response observed after the booster dose demonstrates the persistence of immunity in virtually all young adults vaccinated at the age of 8-10 with three paediatric doses of Engerix-B.

Epidemiology of hepatitis B in Canadian blood donors

BACKGROUND

The residual risk of hepatitis B is higher than for other markers such as human immunodeficiency virus and hepatitis C virus in nonendemic countries. Evaluating the potential for further risk reduction requires a better understanding of the relationship between donor selection criteria, immigration from endemic countries, and public health vaccination strategies.

STUDY DESIGN AND METHODS

Age and sex trends of hepatitis B surface antigen (HBsAg)-positive donors from 1997 to 2006 were analyzed using a Poisson model. All HBsAg-positive donors in 2005/2006 plus four matched control donors for every HBsAg-positive donor who participated were invited to participate in a risk factor interview and predictors of HBsAg positivity identified by logistic regression. A survey of 40,000 donors who did not react for all markers asked about vaccination history and country of birth.

RESULTS

Most HBsAg-positive donations were from first-time donors (86%), have been decreasing in donors under the age of 30 (p < 0.01), and were correlated with geographic regions with more donors from higher-prevalence countries (p < 0001). Birth in a higher-prevalence country predicted HBsAg positivity (p < 0.01). Fifty-six percent of donors reported being vaccinated for hepatitis including approximately 80 percent of donors under age 30 who reported being vaccinated as part of regular school programs.

CONCLUSION

HBsAg-positive donations are decreasing in donors under age 30, those most frequently vaccinated through provincial vaccination programs. HBsAg-positive donations largely reflect immigration from high-prevalence countries without other deferrable risk factors, mainly chronic cases that will be detected by current testing. Furthermore, risk of incident infections should decrease with increasing vaccination rates in donors, especially the younger cohort now receiving universal vaccination.

Should hepatitis B vaccine be used for infants?

Chronic hepatitis B virus infection causes nearly all the deaths from this virus. As the initial infection occurs without symptoms and decades prior to the onset of cirrhosis and liver cancer, these consequences are rarely recognized as being caused by the virus. Consequently, its public health importance is under-recognized. Safe and effective vaccines have now been available for over 20 years. Concerns have been raised regarding the mercury preservative in vaccines leading to potential toxicity. But the evidence to date does not support any association of hepatitis B vaccine with serious adverse consequences. Protecting infants through immunization is the most effective control strategy. By 2005, over 80% of countries had implemented routine infant immunization. In countries with relatively low rates of hepatitis B virus infection, some have argued to defer immunization until later life. However, these arguments focus on the more visible acute infection. The possible future cost from a single infant infection argues for universal infant hepatitis B immunization--given the very high costs of treating its consequences (e.g., liver transplant) and the very low price of the vaccine.