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Bernard Duval

Publications and source records attributed to Bernard Duval.

At least 19 recordsLinked to original sources
PubMed2006

A review of interventions triggered by hepatitis A infected food-handlers in Canada.

BACKGROUND: In countries with low hepatitis A (HA) endemicity, infected food handlers are the source of most reported foodborne outbreaks. In Canada, accessible data repositories of infected food handler incidents are not available. We undertook a systematic review of such incidents to evaluate the extent of viral transmission through food contamination and the scope of post-exposure prophylaxis (PEP) interventions. METHODS: A systematic search of MEDLINE and EMBASE was conducted to identify published reports of incidents in Canada. An expanded search of a news repository (i.e., transcripts from newspapers and newscasts) was also conducted to identify the location and timing of an incident, which was used to retrieve the related report by contacting local public health departments. Data pertaining to case identification, public health risk, PEP interventions, and associated costs was independently abstracted by two reviewers and summarized according to incidents with and without large PEP interventions. RESULTS: A total of 16 incidents were identified from 1998-2004. There were approximately 3 incidents requiring public notification per year. Only 12.5% of incidents were described in published reports, indicating that published data significantly underestimated the number of incidents and PEP interventions. Data pertaining to the remaining incidents was unpublished, sparse and highly dispersed at the local public health level. Six of the 16 incidents required large PEP interventions to immunize on average 5000 potentially exposed individuals. Secondary transmission was low. Characteristics of incidents requiring large PEP interventions included potentially infectious food handlers working with uncooked food for a prolonged duration in high-volume grocery stores in high-density urban areas. CONCLUSION: Infected food handlers with hepatitis A virus (HAV) requiring public notification are not infrequent in Canada. Published data severely underestimated the burden of PEP intervention. Better and consistent reporting at the local and national level as well as a national data repository should be considered for the management of future incidents.

Canada↗
PubMed2006

Cohort effects in dynamic models and their impact on vaccination programmes: an example from hepatitis A.

BACKGROUND: Infection rates for many infectious diseases have declined over the past century. This has created a cohort effect, whereby older individuals experienced a higher infection rate in their past than younger individuals do now. As a result, age-stratified seroprevalence profiles often differ from what would be expected from constant infection rates. METHODS: Here, we account for the cohort effect by fitting an age-structured compartmental model with declining transmission rates to Hepatitis A seroprevalence data for Canadian-born individuals. We compare the predicted impact of universal vaccination with and without including the cohort effect in the dynamic model. RESULTS: We find that Hepatitis A transmissibility has declined by a factor of 2.8 since the early twentieth century. When the cohort effect is not included in the model, incidence and mortality both with and without vaccination are significantly over-predicted. Incidence (respectively mortality) over a 20 year period of universal vaccination is 34% (respectively 90%) higher than if the cohort effect is included. The percentage reduction in incidence and mortality due to vaccination are also over-predicted when the cohort effect is not included. Similar effects are likely for many other infectious diseases where infection rates have declined significantly over past decades and where immunity is lifelong. CONCLUSION: Failure to account for cohort effects has implications for interpreting seroprevalence data and predicting the impact of vaccination programmes with dynamic models. Cohort effects should be included in dynamic modelling studies whenever applicable.

Adolescent↗
PubMed2006

Chapter 22: Assuring the quality, safety and efficacy of HPV vaccines: the scientific basis of regulatory expectations pre- and post-licensure.

The potential of human papillomavirus (HPV) vaccines will only be realized if the vaccine candidates under development prove to be safe and effective and can be consistently produced to define quality standards. Whilst the responsibility for delivering a safe and effective product rests with the vaccine producer, a vaccine requires a license to allow it to be placed on the market. Licensure is based on an evaluation of the safety and efficacy profile of a vaccine candidate by national regulatory authorities, ideally on the basis of internationally agreed, science-based specifications and procedures. For vaccines, these international specifications are developed by the World Health Organization (WHO). The scientific basis for the regulatory evaluation of the safety and efficacy of HPV vaccines is described in this paper. Once a vaccine is licensed, a second set of criteria are evaluated by a different group of experts to provide advice to national health policy decision makers as to whether the vaccine should be introduced into national immunization programmes. Factors, such as evidence of high disease burden and high cost-effectiveness are taken into account in this second decision-making process.

Humans↗
PubMed2006

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

Ten years after a school-based hepatitis B immunization program was implemented, we conducted a study to assess the impact of the program, vaccine failures, risk factors and the number of cases potentially preventable by the addition of an infant vaccination program. The preteen vaccination program is highly effective. An infant immunization program would bring additional benefits.

Adolescent↗
PubMed2006

Comparison of trip characteristics of children and adults with travel-acquired hepatitis A infection.

We compared the trip characteristics of 84 child and 99 adult cases with travel-acquired hepatitis A (HA). Most pediatric cases had traveled in Asia for more than 30 days and had stayed and eaten most of their meals in the homes of friends and relatives in a country where they had not been born. In contrast, the adults with travel-acquired HA had visited Latin America or the Caribbean for 14 days or less and had stayed primarily in hotels. Specific public health interventions should be undertaken to prevent HA in traveling children.

Adolescent↗
PubMed2006

Solicited adverse events after influenza immunization among infants, toddlers, and their household contacts.

OBJECTIVES: We assessed adverse events, including oculorespiratory syndrome, following influenza immunization during the first year of a publicly-funded program for infants, toddlers and their household members in Canada. METHODS: Parents bringing infants and toddlers for influenza immunization to clinics in Quebec or British Columbia consented to structured telephone interview 5 to 10 days later. One adult provided information for all household members. Symptom experience commencing before and after immunization was assessed. Non-immunized persons also served as a comparison group for immunized household members. RESULTS: Sample included 690 immunized infants and toddlers and 1801 household members, 1374 immunized. Only fussiness, fever, decreased appetite, drowsiness, and nasal congestion/coryza were reported for >5% of infants/ toddlers within 72 hours of immunization, but only arm discomfort was reported among >5% of immunized household contacts. In multivariate analysis, muscle ache was the only systemic symptom reported more often by immunized household members compared to non-immunized persons. Oculorespiratory symptoms were infrequent and there was no difference between immunized and non-immunized household members in their report. Less than 1% of adults required time off work because of adverse events following influenza immunization in the household. Less than 2% of subjects experiencing an adverse event following influenza immunization were considered unlikely to be vaccinated again. CONCLUSION: Influenza vaccine is well-tolerated by infants, toddlers and their household members. Post-marketing observational designs are an expedient way to assess adverse events following influenza immunization. These methods should be established and rehearsed annually in preparation for a pandemic.

Child, Preschool↗
PubMed2005

Interchangeability of two diphtheria and tetanus toxoids, acellular pertussis, inactivated poliovirus, Haemophilus influenzae type b conjugate vaccines as a fourth dose in 15-20-month-old toddlers.

BACKGROUND: Since 1998, all children in Canada have been immunized with a pentavalent diphtheria and tetanus toxoids, acellular pertussis, inactivated poliovirus, Haemophilus influenzae type b conjugate vaccine (DTaP-IPV-Hib) produced by one manufacturer (Pentacel). Recently, another DTaP-IPV-Hib (Infanrix-IPV-Hib) became available. Data on the interchangeability of these products was lacking. METHODS: In this multicentered, observer-blind study, healthy 15-20-month-old children previously immunized with three doses of Pentacel were randomly allocated to receive a single dose of Pentacel or Infanrix-IPV-Hib. Adverse events were documented by diary for 7 days post-immunization and unsolicited adverse events were documented for 30 days. RESULTS: 433 participants were enrolled (mean age 17.1 months). Rates of fever, anorexia and irritability were similar in both groups. Injection-site redness >20 mm (11.5% versus 5.6%; p = 0.038), injection-site pain (52.1% versus 39.4%; p = 0.009) and moderate or greater drowsiness (13.8% versus 7.4%; p = 0.042) were more common after Pentacel than Infanrix-IPV-Hib. The proportions of participants who were sero-protected or who sero-responded were similar for all antigens. Geometric mean titers or concentrations were similar for antibodies against diphtheria toxoid and poliovirus type 3. Geometric mean concentrations or titers were higher in the Infanrix-IPV-Hib group against pertussis toxin (88.5 EU/mL versus 65.6 EU/mL), filamentous hemagglutinin (207.3 EU/mL versus 132.1 EU/mL), pertactin (251.9 EU/mL versus 166.9 EU/mL) and poliovirus type 1 (1293.7 versus 976.2 reciprocal dilution). Geometric mean titers or concentrations were higher in the Pentacel group against H. influenzae type b (29 microg/mL versus 19 microg/mL), tetanus toxoid (5.6 IU/mL versus 4.7 IU/mL) and poliovirus type 2 (1437.3 versus 1134.2 reciprocal dilution). CONCLUSIONS: A booster dose of Infanrix-IPV-Hib after three priming doses of Pentacel is well-tolerated and immunogenic in 15-20-month-old toddlers and can be used interchangeably.

Anorexia↗
PubMed2005

Canadian Association for Immunization Research and Evaluation (CAIRE) guidelines for industry-sponsored clinical trial and epidemiology contract research.

In response to concerns about interactions of academic and public health investigators with industry, the Canadian Association for Immunization Research and Evaluation (CAIRE), in collaboration with six major vaccine manufacturers, developed guidelines for participation in industry-sponsored clinical trial and epidemiology contract research within Canada. Topics addressed include definition of investigators, data ownership, protocol development, data management, data analysis, producing a study report and publication of the results of the study.

Canada↗
PubMed2005

Seroprevalence of hepatitis A infection in a low endemicity country: a systematic review.

BACKGROUND: In Canada--a low endemicity country, vaccines for hepatitis A virus (HAV) are currently recommended to individuals at increased risk for infection or its complications. Applying these recommendations is difficult because the epidemiology of HAV infection is poorly defined, complex, and changing. This systematic review aimed to 1) estimate age-specific prevalence of HAV antibody in Canada and 2) evaluate infection-associated risk factors. METHODS: MEDLINE (1966-2005) and EMBASE (1980-2005) were searched to identify relevant studies for the systematic review. Archives for the Canada Diseases Weekly Report (1975-1991) and Canada Communicable Disease Report (1992-2005) were searched for relevant public health reports. Data were abstracted for study and participants' characteristics, age-specific prevalence, and risk factors. RESULTS: A total of 36 reports describing 34 unique studies were included.The seroprevalence in Canadian-born children was approximately 1% in ages 8-13, 1-6% in 20-24, 10% in 25-29, 17% in 30-39, and increased subsequently. In age groups below 20 and 20-29, age-specific seroprevalence generally remained constant for studies conducted across geographic areas and over time. Compared to Canadian-born individuals, subjects born outside Canada were approximately 6 times more likely to be seropositive (relative risk: 5.7 [95% CI 3.6, 9.0]). Travel to high risk areas in individuals aged 20-39 was associated with a significant increase in anti-HAV seropositivity (RR 2.8 [1.4, 5.5]). Compared to heterosexuals, men having sex with men were only at a marginally higher risk (adjusted odds ratio 2.4 [0.9, 6.1]). High risk for seropositivity was also observed for Canadian First Nations and Inuit populations. CONCLUSION: Results from the current systematic review show that in this low endemicity country, disease acquisition occurs in adulthood rather than childhood. The burden of disease is high; approximately 1 in 10 Canadians had been infected by ages 24-29. The increase in prevalence in young adults coincides with disease importation and increasing frequency of risk factors, most likely behavioral-related ones. Gaps in seroprevalence data were identified rendering the application of current immunization recommendations difficult. A nationwide prevalence survey for all Canadians is needed. This is essential to quantify the effectiveness of current recommendations and conduct cost-effectiveness evaluations of alternative immunization programs, if necessary.

Age Factors↗
PubMed2005

Long-term efficacy of hepatitis B vaccine, booster policy, and impact of hepatitis B virus mutants.

The long-term efficacy of hepatitis B vaccine, long-term effectiveness of hepatitis B immunisation programmes, immune memory induced by hepatitis B vaccine, current booster policies, and impact of hepatitis B virus mutants on immunisation programmes were reviewed at the Viral Hepatitis Prevention Board (VHPB) meeting in Sevilla, Spain, March 2004. The main focus was on universal vaccination programmes with data being presented from Italy, Saudi Arabia, Singapore, Spain, Taiwan, Thailand, The Gambia, and USA (Alaska).

DNA, Viral↗
PubMed2005

Effectiveness of serogroup C meningococcal polysaccharide vaccine: results from a case-control study in Quebec.

BACKGROUND: After a mass-immunization campaign in the province of Quebec, Canada, from 1992 to 1993, a case-control study was conducted to evaluate the effectiveness of the polysaccharide vaccine, while controlling for the potential confounding effects of selected risk factors for serogroup C meningococcal disease. METHODS: The case patient group comprised 74 individuals with confirmed serogroup C meningococcal disease reported after the beginning of the campaign until 31 March 1998. Four control subjects, matched for age and place of residence, were randomly selected from the Quebec health insurance registry. Information on case patients was obtained from regional public health departments. Case patients and control subjects (or a family member) were interviewed by telephone. The analyses were conducted by using conditional logistic regression models. RESULTS: Although the 95% confidence intervals (CIs) were large as a result of the small sample sizes, a high level of protection was found among children aged >or=6 years, during the first 2 years after vaccination (vaccine effectiveness, 95%; 95% CI, 68%-99%; P<.002), and protection remained high during the following 3 years (77%; 95% CI, -364% to 99%; P=.34). For children aged 2-5 years, the estimated effectiveness was positive during the first 2 years (62%; 95% CI, -403% to 97%; P=.47) but was negative during the following period (-74%; 95% CI, -1956% to 85%; P=.66). Among children aged <2 years, there was no evidence of protection. Household crowding and disadvantaged socioeconomic conditions were associated with increased risk of disease. CONCLUSIONS: The polysaccharide vaccine remains a cost-effective option for the short-term protection of school-aged children and adults; however, conjugate vaccines are needed for younger children.

Adult↗
PubMed2005

Comparative long term immunogenicity of two recombinant hepatitis B vaccines and the effect of a booster dose given after five years in a low endemicity country.

BACKGROUND: Few data are available concerning the long term immunogenicity of the pediatric doses of hepatitis B vaccines given to preteenagers. The long term effect of the booster dose in teenagers is unknown. We evaluated the immunogenicity of 2 pediatric hepatitis vaccines after primary vaccination and after a booster dose. METHODS: A prospective 15-year follow-up study of the immunogenicity of 2 hepatitis B vaccines was initiated in 1995 in Quebec City, Canada. One year apart, 1129 children 8-10 years old received Engerix-B 10 microg (EB), and 1126 received Recombivax-HB 2.5 microg (RB) vaccine after a 0-, 1-, 6-month schedule. After 5 years, one-third of the 2 cohorts were randomly selected. A booster dose of EB 10 microg or RB 5 microg was administered according to the vaccine used in the primary immunization. Antibodies were measured before, 1 month after and 1 year after the booster injection. RESULTS: Before the booster dose, anti-HB surface antibody (HBs) was detected in 94.7% of the EB subjects and in 95.2% of the RB subjects (P = 0.85). The geometric mean titer (GMT) was higher in the EB than in the RB group (252 mIU/mL versus 66 mIU/mL, P < 0.0001). One month after the booster, 99.7% of subjects in the EB group and 99.6% in the RB group had a detectable anti-HBs, and 99.0 and 99.3%, respectively, had anti-HBs > or =10 mIU/mL. The anti-HBs GMT was 113,201 mIU/mL in the EB and 16,623 mIU/mL in the RB groups (P < 0.0001). One year after the booster, 99.3% of subjects in the EB group and 100% in the RB group had detectable anti-HBs, and 97.9 and 98.5% respectively, had anti-HBs > or =10 mIU/mL. The anti-HBs GMT was 14,028 mIU/mL in the EB and 3437 mIU/mL in the RB group (P < 0.0001). CONCLUSIONS: The immunity persists for at least 5 years after the primary vaccination with both pediatric vaccines in 99% of children vaccinated at the age of 8-10 years. It confirms that no booster is needed at that point.

Analysis of Variance↗
PubMed2005

Nationwide canadian study of hepatitis a antibody prevalence among children eight to thirteen years old.

BACKGROUND: Hepatitis A vaccines provide consistent, long-lasting protection and have been available for almost 10 years in Canada, but their use remains limited. It is difficult to assess their optimal utilization given that our knowledge of hepatitis A epidemiology in Canada is fragmentary. Unlike the United States, no nationwide study of hepatitis A prevalence has ever been done in Canada. Consequently we do not know the incidence of infection in children and what would be the most appropriate age for hepatitis A vaccination. OBJECTIVE: To estimate the proportion of 8- to 13-year-old children who have been infected with hepatitis A virus (HAV) and the risk factors for this infection on a nationwide scale. METHODS: Children were sampled in 10 Canadian provinces, comprising 5 regions, using random digit dialing methodology with regional stratification. Demographic data and information about risk factors for hepatitis A were collected by the telephone interviewers. Oral fluid samples were self-collected and mailed to the laboratory, where they were tested for anti-HAV IgG. RESULTS: Of 6740 contacted families with a child of required age, 1688 (25%) agreed to participate and answered the questionnaire. From these, 1074 oral fluid samples were received, and 1057 could be analyzed. Anti-HAV IgG was detected in 2.7% of subjects, with variation by region from 0.8 to 3.4%. The parents of 54 subjects (5.1%) reported that their child had previously been vaccinated against HAV. Anti-HAV IgG was present in 2.0% of unvaccinated subjects, among whom antibody prevalence was 19.4% in children born in HAV-endemic countries, 6.1% in Native children and 4.2% in travelers to endemic countries. In multivariate analysis of all subjects, the presence of anti-HAV IgG was significantly associated with birth in an endemic country, travel to an endemic country, Native status (American Indian and Inuit population), female gender and vaccination against HAV. In nonvaccinated, non-Native children born in Canada who did not travel to endemic countries, anti-HAV prevalence was 1.1%. CONCLUSIONS: The risk for hepatitis A during childhood is low in Canada. Almost all teenagers (>97%) would be at risk for infection in case of contact with HAV. Changes in immunization policy against hepatitis A should be considered.

Adolescent↗
PubMed2004

Recurrence risk of oculorespiratory syndrome after influenza vaccination: randomized controlled trial of previously affected persons.

BACKGROUND: Oculorespiratory syndrome (ORS) after influenza vaccination has many features of an allergic reaction. METHODS: The objective of the study was to estimate the recurrence rate of ORS after receipt of either of 2 influenza vaccines available in Canada for the 2002-2003 influenza season in individuals who experienced ORS in 2000 or 2001. We designed a randomized, crossover, double-blind, placebo-controlled trial in which patients received the vaccine and the placebo 7 days apart. Patients were contacted by telephone at 24 hours and seen at 7 days to collect information about the recurrence of ORS symptoms. The 146 patients belonged to 3 groups: group A (46 patients) had ORS in 2000 but were not revaccinated in 2001, group B (50 patients) had ORS in 2000 and were revaccinated in 2001, and group C (50 patients) had ORS in 2001 but not in 2000. Half of the participants received Fluviral S/F (Shire Biologics) and half received Vaxigrip (Aventis Pasteur). The main outcome measure was the risk difference in ORS symptoms in the 24 hours after receiving the vaccine and after receiving placebo. RESULTS: Recurrence attributable to the vaccine occurred in 34% (95% confidence interval, 21%-47%) of patients after receiving Fluviral S/F and in 15% (95% confidence interval, 2%-28%) after receiving Vaxigrip. The rate was twice as high in group A vs groups B and C. The risk of ORS was highest and most significant in group A patients vaccinated with Fluviral S/F. Most cases were mild, with 94% of patients with recurrence indicating that they would still be revaccinated the next year. CONCLUSIONS: Despite high recurrence rates, revaccination of persons previously affected by ORS seems to be safe. Oculorespiratory syndrome is not anaphylactic, and most recurrences are benign. Most patients remain willing to be revaccinated.

Adolescent↗
PubMed2004

Immunogenicity of two paediatric doses of monovalent hepatitis B or combined hepatitis A and B vaccine in 8-10-year-old children.

Hepatitis A and B vaccines are highly immunogenic in three-dose schedules. To obtain an equivalent result in children with two paediatric doses would be of significant benefit. The purpose of this study was to measure the immunogenicity of a two-dose schedule in children with two licensed recombinant HBsAg containing vaccines given at paediatric doses, one of them combined with hepatitis A. Seven-hundred and four healthy school children aged 8-10 years were recruited in an open label study to receive either Twinrix Pediatric (360 El.U HAV antigen; 10 microg HBsAg) or Recombivax (2.5 microg HBsAg) vaccine intramuscularly 6 months apart. The seroconversion (>/=1 mIU/ml for anti-HBs antibodies and >/=33 mIU/ml for anti-HAV antibodies), seroprotection (anti-HBs >/=10 mIU/ml) rates and the geometric mean titers (GMTs) were determined 4-8 weeks after the second dose. The anti-HBs seroconversion rate was 97.1% with Twinrix and 97.2% with Recombivax. The seroprotection rates were 96.5 and 94.4%, respectively (P = 0.17). The GMT was higher with Twinrix than with Recombivax (3248 mIU/ml versus 742 mIU/ml, P < 0.0001). All the children vaccinated with Twinrix seroconverted to HAV and the GMT was 5168 mIU/ml. The obtained results suggest that two paediatric doses of hepatitis vaccines are highly immunogenic in 8-10-year-old children. This schedule could facilitate a greater vaccine acceptance and the addition of hepatitis A vaccine to existing adolescent universal hepatitis B virus immunization programs.

Canada↗
PubMed2003

Randomized, double-blind, placebo-controlled trial to assess the rate of recurrence of oculorespiratory syndrome following influenza vaccination among persons previously affected.

During the 2000-2001 influenza immunization campaign in Canada, an oculorespiratory syndrome (ORS) was recognized as adverse event associated with one of the vaccines administered. The initial surveillance case definition for ORS in 2000-2001 specified onset within 24 h after vaccination and resolution within 48 h after onset; the restriction on the duration of ORS was removed from the case definition for the vaccine distributed during the 2001-2002 influenza season. The implicated vaccine contained large aggregates of unsplit virions; alterations to the manufacturing process for the vaccine distributed during 2001-2002 addressed this. A randomized, double-blind, placebo-controlled trial assessed the safety of the reformulated version in previously affected adults. The trial was halted early, after 61 participants had received an injection (34 had received vaccine, and 27 had received placebo). The vaccine-attributable recurrence rate for onset of ORS within 24 h after injection was 33% (95% confidence interval [CI], 10%-53%); for cases that resolved within 48 h, this rate was 27% (95% CI, 5%-47%). Previously affected persons should be informed of the risk of ORS recurrence but also that episodes of such recurrence are mild and well tolerated.

Adult↗
PubMed2003

Oculo-respiratory syndrome following influenza vaccination: evidence for occurrence with more than one influenza vaccine.

We assessed the occurrence of oculo-respiratory syndrome (ORS) following two influenza vaccines: Fluviral (Shire Biologics) or Vaxigrip (Aventis Pasteur). ORS was identified amongst 5.3 and 4.6% of recipients, respectively (P=0.54). With both vaccines, the risk of ORS was much greater in individuals who had ORS the previous year (2000) than in those without such history. In multivariate analysis, the odds ratio for ORS for patients with a prior history of ORS varied between 9.4 and 9.6 (P<0.001) whereas that comparing Fluviral and Vaxigrip varied between 1.5 and 1.9 (P=0.02-0.05). ORS is an adverse event that is present with more than one vaccine and may be present with any influenza vaccines to a greater or lesser degree.

Adult↗