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Biomedical subjects

B Duval

Publications and source records attributed to B Duval.

At least 19 recordsLinked to original sources
PubMed1999

Protection after two doses of measles vaccine is independent of interval between doses.

The protection provided by one or two doses of measles vaccine was compared, as was the effect of the timing of delivery of the doses on the protection provided. A total of 5542 measles cases occurred in Ontario, Canada, between January 1990 and December 1996. Three controls per case were matched for age and residence. Children who received a single dose at age 15 months and older were 5 times more likely to contract measles than were children who received two doses of vaccine after their first birthday. Among children given two doses of vaccines, the risk of measles was 3 times greater in those who had their first vaccination at age 11 months compared with children who first received vaccine after age 1 year, but the protection was independent of the interval between doses. Delaying the second dose >6 months after the first does not increase protection.

Case-Control Studies↗
PubMed1996

Effectiveness of a whole cell pertussis vaccine in child-care centers and schools.

BACKGROUND: Pertussis has substantially increased in Quebec, Canada, since 1990. We estimated pertussis vaccine effectiveness and vaccine coverage in child-care centers and elementary schools. METHODS: Two retrospective cohort studies were simultaneously conducted. One included 4482 children attending 88 public child-care centers and the other included 3429 pupils in 14 elementary schools. Cough and pertussis symptoms were assessed through a questionnaire and medical records; immunization status was ascertained by examination of written records. RESULTS: In child-care centers 95% of children had received at least three vaccine doses at the beginning of the follow-up; in schools more than 98% of pupils had received at least 4 doses. With > or = 4 doses of vaccine and a standard case definition used for surveillance (cough > or = 2 weeks, > or = 1 pertussis symptom and no other apparent cause for cough), vaccine effectiveness was estimated at 61% (95% confidence interval, 44 to 72%) in child-care centers and at 60% (95% confidence interval, 10 to 82%) in schools. With the same number of doses but a case definition requiring a cough > or = 5 weeks, vaccine effectiveness increased to 71% (95% confidence interval, 49 to 83) in child-care centers and to 86% (95% confidence interval, 66 to 94%) in schools. CONCLUSIONS: The increase in pertussis in Quebec is not caused by a low vaccine coverage. A low vaccine effectiveness may contribute to the resurgence of pertussis in the past decade.

Canada↗
PubMed1995

Measles, mumps, and rubella antibodies in children 5-6 years after immunization: effect of vaccine type and age at vaccination.

The levels of antibody against measles, mumps, and rubella were determined at 5-6 years postimmunization in 468 children vaccinated with two different trivalent vaccines. The proportions of children without detectable antibody levels were 12 and 3.6% for measles (p < 0.001), 14.9 and 7% for mumps (p = 0.006), and 3.3 and 3.1% for rubella (p = 0.88), respectively, in MMR II and Trivirix recipients. A higher proportion of those vaccinated at younger ages had undetectable or low levels of measles antibody. These data indicate that a large proportion of children vaccinated under routine conditions do not have detectable measles and mumps antibody.

Age Factors↗
PubMed1995

Field effectiveness of erythromycin prophylaxis to prevent pertussis within families.

To evaluate the field effectiveness of erythromycin prophylaxis for pertussis within families, a retrospective cohort study was conducted among 246 families. Overall 41% of the subjects (387 of 940) had been sick. The secondary attack rate was 65% for infants younger than 2 years, 54% for those 2 to 4 years old and 39% for children 5 to 9 years old, and it declined thereafter. The secondary attack rate decreased from 25% in families without prophylaxis to 17% in families with prophylaxis. The protection induced by prophylaxis did not vary with age or vaccination status. When prophylaxis was used before the onset of a secondary case, the secondary attack rate was 4% compared with 35% when given after a secondary case (P < 0.001). Erythromycin prophylaxis seems to be efficient in preventing secondary cases but is most useful when administered before the occurrence of the first secondary case.

Adolescent↗
PubMed1995

Seroepidemiologic study of three zoonoses (leptospirosis, Q fever, and tularemia) among trappers in Québec, Canada.

This study was undertaken to evaluate the prevalence of antibodies against Francisella tularensis, Coxiella burnetii, and certain serovars of Leptospira interrogans among trappers in Québec, Canada. Muskrat trapping was identified as a risk factor for F. tularensis infection, whereas having a cat at home apparently protected trappers against infection by L. interrogans. High percentages of control sera were positive for antibodies against C. burnetii (15%) and L. interrogans (5%), most frequently serovar bratislava. This is the first report of human infection by serovar bratislava in North America.

Adult↗
PubMed1995

Need for vaccination of sewer workers against leptospirosis and hepatitis A.

OBJECTIVES: This study compared the prevalence of Leptospira interrogans and hepatitis A virus (HAV) antibodies in serum samples from sewer workers and controls. METHODS: A blood sample was obtained from 76 of the 101 municipal sewer workers (75%) of Quebec City and from two controls matched to each for age and sex. Testing was done for antibodies against serovars of Leptospira icterohaemorragiae, bratislava, hardjo, grippotyphosa, and kennewicki (pomona) and hepatitis A. RESULTS: Sewer workers had a greater prevalence of antibodies against leptospirosis than controls (12% v 2%, P = 0.003). In contrast, antibodies to HAV were not significantly more prevalent among workers than among controls (54% v 49%, P = 0.51). Prevalence of HAV antibodies increased significantly with age both among workers and controls (chi 2 for trend, P < 0.001). In contrast with younger workers, prevalence of HAV antibodies was greater among workers > or = 40 years than among their controls (81% v 65%, P = 0.04). CONCLUSION: Leptospirosis continues to be a problem to sewer workers but hepatitis A is apparently no longer a risk. The likely explanation is that leptospira are still abundant in the sewage system in contrast with HAV, which is only rarely to be found in sewage as a result of the generalised decrease in incidence of hepatitis A in the past three decades. The decision to vaccinate sewer workers against hepatitis A should take into account that it is impossible to avoid all contact with sewage fluid and, despite the fact that the actual incidence of hepatitis A is low, there is a real possibility of sporadic exposure during a future outbreak.

Adult↗
PubMed1993

Frequency of sexually transmitted diseases among university students.

OBJECTIVE: To estimate the incidence rate of sexually transmitted diseases (STDs) among university students and evaluate the associated sociodemographic factors. DESIGN: Mail survey in April 1990. Included in the questionnaire were questions about the subjects' STD experience since their admission to the university and the type and date of the infection. SUBJECTS: Of the 19,682 undergraduate students 2920 subjects, in 10 groups of 292, were randomly selected. A total of 1731 (59.4%) completed the questionnaire. MAIN OUTCOME MEASURES: Estimated annualized incidence rates of genital human papillomavirus infection and Chlamydia infection. RESULTS: The estimated annualized incidence rates of genital human papillomavirus and Chlamydia infections were 2.2% and 1.5% respectively. Among the students who indicated being infected with genital human papillomavirus 59% were 18 to 21 years old (p < 0.05), 76% were women (p < 0.01) and 69% had more than one sexual partner (p < 0.01). No statistically significant associations were observed between age, sex and Chlamydia infection. On the other hand, 95% of the cases of Chlamydia infection were found among those who had more than one sexual partner (p < 0.01). CONCLUSION: University students continue to have sexual activities at risk for STDs and should be specifically targetted by general practitioners and health services in an effort to slow the spread of STDs.

Adolescent↗
PubMed1993

[Factors associated with at-risk anal relations in homosexual HIV-seropositive men].

This pilot study proposes an index to quantify the intensity of high-risk anal sex and presents factors associated with this practice among 65 homosexual men with HIV infection. All of them answered a self-administered questionnaire. Using multiple logistic regression, we first compared those who had had safe sex in the past six months to those who had had unsafe sex. Variables significantly associated with unsafe sex are: drugs and/or alcohol use with sex, and less favorable attitude towards condom use. Finally, multiple linear regression analysis among respondents who had had unsafe sex indicated that the following factors are associated with higher levels of unsafe sex: men between the ages of 32 and 38, satisfied with their social life, non-smokers, with a less favorable attitude towards condom use, and with few social relationships. These results must be interpreted with caution because of the small number of respondents.

Attitude↗
PubMed1992

Understanding physicians' decision to perform a clinical examination on an HIV seropositive patient.

The main purpose of this study was to identify the psychosocial factors explaining a physician's decision to perform a clinical (physical) examination of an HIV seropositive patient. Eight hundred seventy-nine physicians completed a questionnaire investigating psychosocial variables derived from the theories of Ajzen and Triandis. The mean intention to perform a clinical examination was quite positive (5.4 on a 7-point scale). The regression of intention on all variables yielded an adjusted R2 of .499. Among few significant predictors, by far the most important was the perceived norm among fellow physicians regarding performance of the clinical examination. It is concluded that educational interventions aimed at the physician population should focus on the social role and personal efficacy of physicians regarding this type of clinical examination rather than giving information concerning the low risk of contracting the HIV.

Attitude of Health Personnel↗
PubMedDate not supplied

University students' intention to seek medical care promptly if symptoms of sexually transmitted diseases were suspected.

The aim of this study was to identify the factors explaining intention to seek medical care promptly if STD symptoms were suspected. A random sample of 1617 undergraduate students completed a questionnaire assessing intention, attitude, perceived norm among friends, perceived behavioral control, and risk of disease, along with different socio-demographic variables. The regression of intention on all variables yielded an adjusted R2 of 0.32 (P < 0.0001). The factors explaining this variance were the perceived advantages, easiness, and social norm among friends regarding seeking medical care promptly, age, and gender. Perception of risk to delay seeking medical care and perceived personal risk of getting STDs were not significant variables. Overall, the results indicate the need to develop programs for male first-year students. These programs will have to influence the attitude, that is, the perceived advantages of seeking medical care promptly if STD symptoms are suspected. Seeking advice from students' friends, and perception of these friends as a significant reference source if STD symptoms are suspected, should also be promoted.

Adolescent↗
PubMedDate not supplied

[Major measles epidemic in the region of Quebec despite a 99% vaccine coverage].

The 1989 measles outbreak in the province of Quebec has been largely attributed to an incomplete vaccination coverage. In the Quebec City area (pop. 600,000) 1,363 confirmed cases of measles did occur. A case-control study conducted to evaluate risk factors for measles allowed us to estimate vaccination coverage. It was measured in classes where cases did occur during the outbreak. This population included 8,931 students aged 5 to 19 years old. The 563 cases and a random sample of two controls per case selected in the case's class were kept for analysis. The vaccination coverage among cases was at least 84.5%. Vaccination coverage for the total population was 99.0%. Incomplete vaccination coverage is not a valid explanation for the Quebec City measles outbreak.

Adolescent↗
PubMedDate not supplied

[Selection of target behaviors before planning health education objectives: application to prevention of STD in teenagers].

This article describes a semi-quantitative technique enabling the person responsible for the planning of a health education program to select the behaviour that should be targeted. The technique is adapted from Morley and used within Green's health education planning model. The relevant behaviours are ranked according to their importance and their changeability. A global weight is calculated for both by multiplying the weights attributed for each criterion of importance and changeability. This method is illustrated by an application for sexually transmitted diseases in teenagers. Calculations are made both for younger and older teenagers.

Adolescent↗