RESUMEN

BACKGROUND: In Canada, inactivated hepatitis A vaccines are targeted selectively at those at increased risk for infection or its complications. In order to evaluate the need for routine hepatitis A vaccination programs in Vancouver for street youth, injection drug users (IDUs) and men who have sex with men (MSM), we determined the prevalence of antibodies against hepatitis A virus (HAV) and risk factors for HAV in these groups. METHODS: The frequency of past HAV infection was measured in a sample of Vancouver street youth, IDUs and MSM attending outreach and STD clinics and needle exchange facilities by testing their saliva for anti-HAV immunoglobulin G. A self-administered, structured questionnaire was used to gather sociodemographic data. Stepwise logistic regression was used to evaluate the association between presumed risk factors and groups and past HAV infection. RESULTS: Of 494 study participants, 235 self-reported injection drug use, 51 were self-identified as MSM and 111 met street youth criteria. Positive test results for anti-HAV were found in 6.3% of street youth (95% confidence interval [CI] 2.6%-12.6%), 42.6% (95% CI 36.2%-48.9%) of IDUs and 14.7% (95% CI 10.4%-19.1%) of individuals who denied injection drug use. Among men who denied injection drug use, the prevalence was 26.3% (10/38) for MSM and 12% (21/175) for heterosexuals. Logistic regression showed that past HAV infection was associated with increased age and birth in a country with high rates of hepatitis infection. Injection drug use among young adults (25-34 years old) was a significant risk factor for a positive anti-HAV test (p = 0.009). MSM were also at higher risk for past HAV infection, although this association was nominally significant (p = 0.07). INTERPRETATION: Low rates of past HAV infection among Vancouver street youth indicate a low rate of virus circulation in this population, which is vulnerable to hepatitis A outbreaks. An increased risk for HAV infection in IDUs and MSM supports the need to develop routine vaccination programs for these groups also.

Asunto(s)

Asunto(s)

RESUMEN

BACKGROUND: Tetanus-diphtheria toxoids (Td) booster immunization is generally recommended for Grade 9 students (14- to 16-year-olds) but targeting younger students may enhance vaccine uptake or facilitate simultaneous vaccinations. However, earlier vaccination might cause greater side effects. This study was undertaken to compare the safety of Td vaccinations in students in Grade 6 (11 to 12 years old) and Grade 9. METHODS: A controlled, sequential assessment of Td vaccine, adsorbed, was conducted in one urban school district, starting with Grade 9 students. Grade 6 students were given Td concurrently with Dose 3 of hepatitis B vaccine. Adverse effects were assessed during visits 2 days after vaccination. Participation criteria, immunization technique and assessment procedures were standardized. RESULTS: Of 410 students vaccinated, 204 in Grade 9 and 206 in Grade 6, 391 (95.4%) were assessed in person. Nineteen missed follow-up visits but telephone interviewers established that none missed school because of vaccine side effects. At follow-up Grade 6 students more often reported deltoid pain with arm movement (35.2% vs. 10.8%, P < 0.001). Injection site redness > or = 50 mm in diameter was present in 12.2% of Grade 6 and 3.6% of Grade 9 students (P < 0.001) whereas swelling > or = 50 mm diameter was present in 22.4 and 10.8%, respectively (P < 0.01). Fewer than 10% of subjects took analgesics for injection site pain. Only 5 students (1.3%) rated Td site morbidity as severe/unacceptable. Hepatitis B site morbidity was minimal in comparison. CONCLUSION: Td boosters were moderately reactogenic in adolescents. Younger students more often experienced injection site morbidity but considered it bearable. Booster immunizations can reasonably be offered within the age range of 11 to 16 years.

Asunto(s)

RESUMEN

To determine the prevalence of hepatitis A virus (HAV) infections in children in a large urban center, a point prevalence survey was conducted using a novel, ultrasensitive assay for HAV-specific IgG in saliva. A structured sample of 224 grade-six students (5.8% of grade registrants) was obtained from 23 schools throughout Vancouver. All students provided saliva samples adequate for testing. The anti-HAV prevalence rate was 7.1% (95% confidence interval, 4.1%-11.3%). Among 167 Canadian-born students, only 5 (3%) were positive, whereas among 57 students born elsewhere, 11 (19.3%) were positive (P < .001), with circumstances in the latter group supporting infection prior to emigration. No clustering of positive persons was evident. The cumulative risk of HAV infection in Canadian-born children was low through age 11-12 years even in less affluent parts of the city, speaking against a need for routine use of HAV vaccine in this setting.

Asunto(s)

RESUMEN

Although detection of disease-induced hepatitis A virus (HAV)-specific antibodies in saliva has been successfully utilized in a few epidemiological studies, available assays fail to detect lower salivary anti-HAV levels associated with vaccine-induced immunity. We present a new capture enzyme immunoassay which employs a three-layer antibody recognition system. Evaluation of paired saliva-serum specimens from 1,025 international travellers, 134 other volunteers, and 91 hepatitis A vaccine recipients demonstrated 99.6% (95% confidence interval, 98.4 to 99.9) specificity and 98.7% (95% confidence interval, 97.7 to 99.4) sensitivity of this salivary assay in differentiating between immune and susceptible individuals, compared with serum-based methods. We conclude that this assay is sufficiently sensitive for reliable detection of both vaccine- and infection-induced HAV-specific immunoglobulin G in saliva, even when corresponding anti-HAV levels in serum are very low (< 1 IU/ml).

Asunto(s)

RESUMEN

A prospective, two center study of 319 children was undertaken to assess responses to booster immunization in healthy 18-month-olds who completed primary immunization 12 months earlier with Haemophilus influenzae type b (Hib) conjugate vaccine (either HbOC or PRP-T). Interchangeability of these products as boosters was also assessed, using combination products containing diphtheria, pertussis and tetanus components. The study was randomized and evaluator blinded. Sera obtained prior to booster vaccination and 4 weeks later were tested for anti-PRP using an IgG-specific enzyme immunoassay. Pre-immunization anti-PRP levels were low: unmeasurable levels (< 0.06 microgram ml-1) were present in 47% of those primed with HbOC and 35% of those primed with PRP-T (P < 0.05). Most children responded strongly to booster vaccination. Interchanging the products had no detrimental effect. Children who lacked measurable antibody prior to re-vaccination had significantly weaker responses 4 weeks afterward. Earlier Hib booster vaccination should be considered in Canada to avoid low anti-PRP trough levels. Extended follow-up of antibody levels and vaccine protective efficacy is also advisable given the observed heterogeneity of responses to booster vaccination.

Asunto(s)

RESUMEN

The effects of age, sex, and possible prior exposure to serogroup C meningococci on group C-specific antibody levels (total and functional) were examined in 2- to 19-year-olds just before and 1 and 12 months after immunization with divalent (groups A + C) meningococcal capsular polysaccharide vaccine. Only age was found to have a significant effect on antibody levels. At 1 month, only 50% of 2- to 6-year-olds had detectable serum bactericidal antibody, in contrast to 84.1% and 96.3% of 9- to 12- and 13- to 19-year-olds respectively. By 12 months, only 20%, 40.9%, and 53.8% of subjects in these age groups had serum bactericidal antibody, suggesting that current meningococcal C polysaccharide vaccines provide only short-term protection. However, the drop in total specific antibody levels (by EIA) was less pronounced. Persistence of antibodies detectable by EIA (but not serum bactericidal antibodies) suggests that this vaccine may also give rise to antibodies of low affinity or directed to nonfunctional (nonprotective) epitopes (or both).

Asunto(s)

Asunto(s)

RESUMEN

The immunogenicity of Haemophilus influenzae type b polysaccharide-protein conjugate vaccines in congenitally asplenic children is unknown. The short-term immunogenicity of the H. influenzae type b polysaccharide-diphtheria toxoid conjugate vaccine was therefore assessed in 10 children with congenital asplenia by measuring antipolyribosyl-ribitol phosphate antibody titers. An excellent antibody response was seen in 9 children (mean geometric titer in responders after immunization 44.7 micrograms/mL; range, 2.59-402). The remaining child responded to a booster dose. Further studies are required to assess whether H. influenzae type b conjugate vaccines are immunogenic in infancy in the presence of congenital asplenia.

Asunto(s)

RESUMEN

We developed a sensitive double-sandwich ELISA assay for neutrophil elastase (NE) using affinity-purified NE antibody. The assay was capable of detecting NE levels of 0.2 ng/ml and was used to determine NE in bronchoalveolar lavages (BAL) of 12 healthy subjects (6 nonsmokers and 6 smokers) with a mean age of about 27 yr. NE levels in the unconcentrated cell-free supernatant of BAL, subjected to high-speed centrifugation (17,000 x g for 30 min) to sediment subcellular debris, were similar in the smokers who abstained overnight from smoking and in the nonsmokers (24.4 +/- 13.9 versus 23.7 +/- 12.3 ng/mg [SD] albumin). NE levels were significantly higher in lavage fluid not subjected to high-speed centrifugation, reflecting the presence of NE bound to subcellular debris that was sedimented by high-speed centrifugation. Concentration by ultrafiltration through a Millipore CX-10 filter was accompanied by loss of protein with a relatively greater loss of NE than albumin, resulting in lower NE/albumin ratios in concentrated than in unconcentrated lavage. It is therefore recommended that NE levels be determined on unconcentrated BAL after high-speed centrifugation to sediment subcellular debris.

Asunto(s)

RESUMEN

To evaluate whether epithelial damage of airways in asthma could be related to diminished levels of the low molecular weight bronchial leukocyte proteinase inhibitor (BLPI) in airways, we determined BLPI in bronchial washings of 13 asthma patients and 13 healthy subjects, using a sensitive enzyme-linked immunoassay. The patients had asthma due to western red cedar and had bronchial washings done 24 to 48 hours after a mild to moderate asthmatic reaction induced by inhalation challenge. We did not find significant differences in BLPI concentrations in lavage fluid of asthma patients and healthy control subjects. The ratios of BLPI to albumin levels in bronchial washings appeared to be lower among asthmatic patients, but this difference was mainly due to an increase in albumin levels in lavage fluid in asthma. In addition, there were no significant differences in BLPI levels in washings obtained from main and segmental bronchi in both control subjects and asthma patients.

Asunto(s)

RESUMEN

Two hundred twenty-seven workers in a western red cedar sawmill underwent methacholine bronchoprovocation testing at least 2 times during 3 surveys over a 2-yr period. At the first survey, workers completed a respiratory and occupational questionnaire, performed spirometry, gave serum for measurement of plicatic acid-specific IgE antibodies by radioallergosorbent testing, and had skin prick tests to detect atopy. Bronchial hyperresponsiveness was present initially in 18% of the workers. Approximately 15% of those with initially no hyperresponsiveness developed hyperresponsiveness during the follow-up period; 15% of those with initial hyperresponsiveness also lost it during follow-up. Development of hyperresponsiveness tended to coincide with a decrease in level of pulmonary function, whereas loss of hyperresponsiveness was associated with improvement in pulmonary function. Workers with either persistent bronchial hyperresponsiveness or with varying responsiveness had a higher prevalence of plicatic acid IgE antibodies and lower levels of initial pulmonary function than did workers with persistent nonresponsiveness. Workers with persistent hyperresponsiveness had higher initial estimated total airborne dust exposure than did other workers. Age, duration of sawmill employment, atopy, race, and cigarette smoking did not influence the occurrence of hyperresponsiveness. Levels of plicatic-acid-specific IgE antibodies did not change substantially over the 2 yr. These results indicate that immunologic sensitivity to plicatic acid and change in airway caliber are associated with the occurrence of bronchial hyperresponsiveness in cedar workers.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)