Search PubMed⌕ Search

Biomedical subjects

Bernard Duval

Publications and source records attributed to Bernard Duval.

34 records · Page 2Linked to original sources
PubMed2003

Ocular and respiratory symptoms attributable to inactivated split influenza vaccine: evidence from a controlled trial involving adults.

In 2000, an influenza vaccine was associated with unusual ocular and respiratory symptoms (known as "oculorespiratory syndrome" [ORS]) that possibly were due to numerous microaggregates of unsplit viruses present in the product. We assessed the potential for an improved vaccine formulation (for use in 2001-2002) to cause ORS and other symptoms in adults, using a double-blind, randomized, crossover study design. Symptoms were ascertained 24 h after 622 doses of vaccine and 626 doses of saline placebo were injected. The risk of ORS was 6.3% after vaccine injection and 3.4% after placebo injection, which yielded a significant vaccine-attributable risk of 2.9% (95% confidence interval, 0.6-5.2). ORS symptoms were mild. Significant differences in risk after injection of vaccine versus placebo existed for ocular soreness and/or itching (2.4%), coughing (1.6%), and hoarseness (1.2%). Vaccine-attributable general symptoms were infrequent. We conclude that certain mild oculorespiratory symptoms were triggered by an influenza vaccine that was otherwise minimally reactogenic and, hence, that such symptoms might be associated with influenza vaccines in general.

Adult↗
PubMed2003

Unique roles of a data and safety monitoring board in vaccine safety trials with compressed timelines and urgent implications.

Studies with urgent implications for public policy and programs represent a special case for monitoring boards, whose responsibilities must include ensuring applicability to policy making and timely communication of results as well as data and safety monitoring. We recently conducted two preseason evaluations of an influenza vaccine, results of which would influence the supply of vaccine for the Canadian annual program. Only 12 weeks were available for planning the studies and 6 weeks for fieldwork and data analysis. The enlisted board played key roles in determining appropriate study design, setting and enforcing rules for study initiation and early termination, monitoring safety, and encouraging timely dissemination of results. An extended role in data monitoring would have been desirable. Providing a safety valve for inevitable tensions between investigators and sponsor was an understated but significant role. Lessons from our experience will be particularly pertinent to future studies of pandemic influenza vaccines.

Canada↗
PubMed2003

[Public health: the control of meningococcal disease in Quebec].

A first outbreak of serogroup C meningococcal disease occurred in the province of Quebec in 1990-1992 and lead to a mass immunization campaign using polysaccharide vaccines. In 2001, a second outbreak was identified and a mass vaccination campaign was carried out, using the newly licensed conjugate vaccine. Clinical, epidemiological, economic and social studies were instrumental in the decision making for implementing these control programs.

Disease Outbreaks↗
PubMed2003

Pertussis resurgence in Canada largely caused by a cohort effect.

BACKGROUND: Beginning in 1990 Canada experienced a resurgence of pertussis. Changes in incidence and hospitalization according to age in the province of Quebec between 1983 and 1998 were examined to assess the presence of a cohort effect resulting from a poorly protective vaccine. METHODS: The source of data on incident cases was pertussis notifications to the Quebec Ministry of Health and Social Services. Hospitalization data were extracted from the administrative database that collects information on each hospitalization. RESULTS: The mean annual incidence before 1990 was 3.8 cases per 100,000 population which increased to 37.2 thereafter. Infants had the smallest increase (2.7-fold) when compared with children between 1 and 19 years who experienced a 9- to 15-fold increase and with adults (22.5-fold). The mean annual hospitalization rates increased from 2.7 per 100,000 before 1990 to 5.2 afterward. Ninety percent of hospitalizations occurred in children <5 years of age. The proportion of cases in 0- to 4-year-old children decreased, whereas it increased steadily in all other age groups during the entire study period. Between 1990 and 1998 the median age of cases shifted from 4.4 to 7.8 years. Pertussis affected predominantly children who were immunized with a vaccine introduced in the mid-1980s. The evolution of the age distribution of cases paralleled the aging of this cohort with a slow but steady drift of disease from early childhood to adolescence. CONCLUSION: The sudden increase in pertussis incidence in Canada can be largely attributed to a cohort effect resulting from a poorly protective pertussis vaccine used between 1985 and 1998.

Adolescent↗
PubMed2002

Preadolescent non- and hyporesponders following three doses of hepatitis B vaccine need only one more dose.

A small proportion of healthy children fail to develop antibodies against hepatitis B after three doses of vaccine. Few data are available regarding the optimal re-immunization strategy. We measured the immune response 1 month after a single supplementary dose of recombinant hepatitis B vaccines in 18 young preadolescents who were non- or hyporesponsive after a regular primary course of three doses of recombinant hepatitis B vaccines. Among them, 100% seroconverted and 89% reached the seroprotective titer of 10 milli-International Units (mIU)/ml. Most healthy children, particularly if they are hyporesponders, will have reached the seroprotective level after one dose and will not need further injections.

Child↗
PubMed2002

Low risk of recurrence of oculorespiratory syndrome following influenza revaccination.

BACKGROUND: During the 2000-2001 influenza vaccination season, a new adverse event associated with the influenza vaccine, called oculorespiratory syndrome (ORS), was identified in Canada. We examined the risk of recurrence of ORS for individuals affected in 2000-2001 who were revaccinated in the community setting in 2001-2002. METHODS: We conducted a telephone survey in May 2002 in which participants were asked whether they had been revaccinated in the 2001-2002 immunization season and whether they had experienced any recurrence of ORS or any other adverse event. Eligible individuals (n = 609) included residents of British Columbia aged 18 years or more who had reported any type of adverse event associated with the influenza vaccine in 2000 and who had participated in a survey in September 2001 that characterized their adverse event experience. RESULTS: The response rate to this survey was 92% (561 of 609 people approached). Of the 561 participants, 202 were revaccinated in 2001. Among the 202 revaccinated, 122 individuals had previously reported ORS in 2000: 40 had described their ORS experience in 2000 as mild (present but not bothersome), 44 as moderate (interrupting daily activities), 35 as severe (preventing daily activities) and 3 did not provide specific details. Six of the 122 individuals experienced a recurrence of ORS following revaccination. The estimated risk of recurrence for ORS following revaccination in the community setting was 5% (95% confidence interval 2.2%-10.5%). Four of the 6 individuals described their ORS recurrence in 2001 as milder than the ORS they had experienced in 2000. INTERPRETATION: We found a low risk of recurrence of ORS for individuals previously affected in 2000 when they were revaccinated in 2001, including those whose ORS in 2000 had prevented daily activities but was not clinically severe. Health care providers should be confident in the safety of recommending revaccination of these individuals. As with all vaccines, however, a detailed risk-benefit assessment should be undertaken before revaccination of people whose previous adverse event experience may have included collapse, respiratory difficulty (including throat tightness) and/or chest discomfort requiring emergency intervention.

Aged↗
PubMed2002

Skin testing to evaluate oculo-respiratory syndrome (ORS) associated with influenza vaccination during the 2000-2001 season.

A syndrome of red eyes and respiratory symptoms was noted following receipt of influenza vaccine in Canada during the 2000-2001 influenza season. We conducted intra-dermal skin testing to determine if oculo-respiratory syndrome (ORS) was related to failure of the splitting process during vaccine manufacturing, if it was associated with a particular viral strain and to identify individuals at risk for subsequent ORS reaction. Skin testing with minute quantities of vaccine antigen induced ORS symptoms at a higher rate amongst persons previously affected by this syndrome compared to previously unaffected persons. Skin test reaction size or quality could not identify persons at risk of ORS. Skin testing could not identify a specific strain or the stage in the manufacturing process during which the trigger may have been introduced.

Adult↗
PubMedDate not supplied

Ineffectiveness of the current strategy to prevent hepatitis A in travelers.

BACKGROUND: Each year, a large number of Canadians travel to regions of the world where hepatitis A remains endemic. Many of these travelers are not immune and the current preventive strategy relies wholly on self-referral to a travel clinic. All of the costs associated with such a visit are assumed by the traveler. We estimated the effectiveness of this strategy. METHODS: This case-control study included 108 travel-related hepatitis A cases with onset of disease between 1997 and 1999 and 620 controls who traveled during the same period. RESULTS: Hepatitis A was strongly associated with high-risk travel (Odds Ratio = 7.2, 95% Confidence Interval 1.76-29.4), but only 7% of cases were found in this category. The risk of hepatitis A was 5 times lower in travelers who visited a travel clinic than in those who did not (80% efficacy). However, only 14% of the controls visited a travel clinic. As a result, the effectiveness of the current strategy is estimated to be 11% (80% of 14%). CONCLUSIONS: Hepatitis A in travelers can be prevented effectively by attendance at a travel clinic. Unfortunately, most travelers do not visit such clinics prior to departure. Even if all high-risk travelers were to visit a travel clinic and receive vaccination, this would have negligible impact on the number of travel-related hepatitis A cases (approximately 7% reduction). The current strategy for the prevention of hepatitis A in travelers is ineffective and should be reexamined.

Adult↗
PubMedDate not supplied

A population-based comparison between travelers who consulted travel clinics and those who did not.

BACKGROUND: Travel to hepatitis A-endemic countries is frequent among North Americans. Such travel carries significant risks for the individuals themselves and for the general population. We documented the patterns of use of travel clinics in a large Canadian adult population. METHODS: Travelers who had visited a hepatitis A-endemic country between 1990 and the time of the survey in 1999 were eligible. Subjects were identified from a representative sample of 4,002 adults from the two largest Canadian provinces. They were contacted by random digit dialing and interviewed by telephone. RESULTS: Only 15% of trips had been preceded by a visit to a travel clinic. The probability of visiting a travel clinic was approximately 10 times greater for travelers considered to be in the high-risk category than for those in the low-risk category, but the former represented only 2% of the total. The probability of visiting a travel clinic was approximately 23 times greater for travelers who were aware of the health risks in their country of destination. Income level was not associated with attendance at a travel clinic, and cost was rarely mentioned as a reason for not attending such a travel clinic before departure. CONCLUSIONS: Each year, millions of Canadian travelers go to hepatitis A-endemic countries without consulting a travel clinic. Active steps must be taken by public health authorities to improve their utilization of health services and prevent the accrued health risk for these travelers.

Adult↗
PubMedDate not supplied

Impact of vaccine cost and information about complications of varicella on parental decision regarding varicella vaccine.

BACKGROUND: The influence of providing information about complications of disease and vaccine cost on parental decision to vaccinate against varicella was assessed. METHOD: During telephone interviews of 330 parents of infants aged 9 months, parents were asked if they would agree to have their child vaccinated and were presented information first about varicella complications and then about cost of the vaccine. RESULTS: When complications were explained but information about cost was not, 94% of parents were favourable toward having their child vaccinated. When complications were not explained but cost was presented, this percentage was only 34%. When both cost and complications were presented, 60% of parents were favourable toward the vaccine. INTERPRETATION: In improving receptivity towards varicella vaccine, parents should always be presented data regarding varicella complications by their health care provider.

Chickenpox↗
PubMedDate not supplied

[Why are some children incompletely vaccinated at the age of 2?].

OBJECTIVE: A survey was conducted in the Province of Quebec to document the factors associated with an incomplete immunization status among 2-year-old children. METHODS: Parents of 430 completely and 266 partially vaccinated children selected from the computerized vaccination register agreed to participate. RESULTS: The non-simultaneous administration of the 2nd MMR and 4th DPT-P-Hib at 18 months of age was responsible for 46% of incompleteness. The following characteristics were significantly associated with an incomplete immunization status: being a single parent, > or = 2 children in the family, an older age at first immunization (> or = 3 months), parent's preference for postponing the second vaccine when two injections are scheduled for the same visit, perception of lack of information about vaccination, and disagreement with immunization recommendations. CONCLUSION: One of the key points of this study is the impact of the non-simultaneous administration of the two vaccines at 18 months. Factors such as being a single parent and older age at first immunization might be used to design an early intervention for children who are most likely to be incompletely immunized. Even if parents are favourable towards immunization, they need to be well informed about the associated risks and benefits.

Diphtheria Toxoid↗
PubMedDate not supplied

Varicella vaccine: factors influencing uptake.

BACKGROUND: In Canada, varicella vaccine is recommended but its uptake has been low. In contrast to most other recommended paediatric vaccines, this one is not currently provided free of charge in all provinces and territories in Canada. OBJECTIVE: To evaluate the rate of health care provider offer of varicella vaccine to parents and the most important determinants of parental decision to accept the offer. METHODS: A structured questionnaire was administered by phone interview to parents of children aged 14 to 17 months in the Quebec City area where the vaccine is not publicly funded. RESULTS: Among the 477 participants, 37% had been offered the vaccine by their health care provider: 45% when the provider was a paediatrician and 29% for general practitioners or public health clinics. Only 13% of offers included information on the risk of varicella complications, the cost, efficacy and safety of the vaccine. By decreasing order of importance, the factors that positively increased parental decision to use varicella vaccine included: information on vaccine safety, a positive recommendation and a higher family income. CONCLUSION: Despite a recommendation for universal vaccination, varicella vaccine is not broadly offered and few offers contain all the information both needed to elicit proper consent and correlated with a positive uptake.

Adult↗
PubMedDate not supplied

[Usefulness of a vaccination registry and the management of consent: the case of Quebec].

CONTEXT: The Quebec Public Health Act provides for the creation of a central vaccination registry. However, details of how such a registry would be used have not been established. This study seeks to document the opinion of both the public and of health workers about the usefulness of the registry, consent for enrolment, access to the data and the right of withdrawal. METHODS: Individual interviews and discussion groups were held with parents, senior citizens and health workers. The material collected was recorded, transcribed and analyzed qualitatively using MAXQDA software. RESULTS: The usefulness of a vaccination registry seems to meet with general agreement, as does the idea of obtaining broad-based consent at enrolment. However, this consensus starts to crumble on questions of determining the rules governing access to the registry. Some favour limited consent, authorizing each access, while others, more numerous, prefer a broad-based consent giving access to all individuals authorized under the law. Opinions are even more divided on the question of giving the user the right to not record certain vaccines, particularly when they may be considered sensitive and a possible cause of prejudice. DISCUSSION: The more the information is considered sensitive by users, the more they seek to have access to the register and entries into it controlled and to apply some kind of specific consent, limited in scope, rather than a broad-based consent. This study lets us draw lessons applicable to the computerization and networking of medical records.

Access to Information↗
PubMedDate not supplied

[Portrait of the formation in vaccination training offered to Quebec nurses in the workplace].

INTRODUCTION: Nurses carry out essential functions in the area of immunization in Québec and their role has broadened considerably since January 2003, following legislative modifications. However, the training received may not always allow nurses to fill this role satisfactorily. This study seeks to document the training in immunization offered to Québec nurses in the workplace. METHOD: A questionnaire was mailed to the directors or heads of nursing care (DSI/RSI) in 477 health care establishments in Québec in March 2003. RESULTS: Health care establishments in Québec offer more training to nurses on the job (68%) than at the moment of hiring (43%). These percentages vary widely according to the type of establishment. More than 90% of the local community service centres (CLSC) that responded offer training to their nurses. The indications/contraindications of immunization products and emergencies related to vaccination represent the themes most frequently dealt with. Only 38% of respondents affirm that the nurses in their institution are "very favourable" to vaccination. DISCUSSION: Almost all Québec CLSCs, which is where most immunization activities are carried out, offer training in vaccination to their nurses. On the other hand, few hospital centres (CH) and long-term care establishments (CHSLD) do so. Further documentation should be carried out on the impact of less than optimal training on the promotion of immunization programs by nurses.

Attitude of Health Personnel↗