The effect of using short versus detailed self-administered questionnaires on the estimate of illicit drug use among young adults

We compared two study instruments in use in the Israel Defence Forces to ascertain the prevalence of illicit drug use: a short versus a detailed self-administered anonymous questionnaire. A relatively lower estimate of illicit drug use was found among subjects that answered the short questionnaire. The difference was noted for lifetime prevalence of illicit drug use for women but not for men (6.5% of women reported ever use of illicit drugs using the detailed questionnaire versus 2.1% of women using the short questionnaire, p = 0.002); for prevalence of infrequent illicit drug use (3.3% of men and 3.4% of women reported less than monthly use of illicit drugs using the detailed questionnaire versus 0.2% of men and none of the women with the short questionnaire; p = 0.004 and p < 0.001, respectively), but not for frequent use (i e monthly or more). There was no difference in the percent of subjects that admitted that they knew where to get drugs. We conclude that the short questionnaire in routine use for more than a decade is a useful instrument when compared with the detailed questionnaire, in that the yield of important information such as frequent illicit drug use is similar. This is achieved with the benefit of greater convenience and ease of application to large samples at a lower cost.

Norwalk virus gastroenteritis among Israeli soldiers: lack of evidence for flyborne transmission

BACKGROUND

Paired sera collected from subjects before and after a fly-control intervention trial conducted in the Israel Defense Force (IDF) were tested for seroconversion to Norwalk virus (NV) to examine the role of NV as a cause of diarrhea in this population and to ascertain whether flies might also be implicated in transmission.

MATERIALS AND METHODS

An enzyme-linked immunosorbent assay (ELISA), using recombinant NV capsid proteins (rNV) as antigen was employed to determine the seroconversion rate in a sample of 444 subjects.

RESULTS

During 11-week field training cycles, 18% of IDF soldiers who were tested had an NV infection defined as a > or = 4-fold rise in antibody, yielding a cumulative incidence of nearly one infection (0.95) per soldier per year. The rate of seroconversion was nearly twice as high among soldiers who recalled having diarrhea as among those who did not, but the rates did not differ significantly between soldiers in the fly intervention areas and those in the control areas.

CONCLUSION

NV is a common cause of enteric infections and diarrhea among Israeli soldiers who serve under field conditions, but unlike infections with Shigella and enterotoxigenic Escherichia coli, transmission of NV cannot be interrupted with an aggressive program of fly-control.

Prospective cohort studies of shigellosis during military field training

Epidemiological and clinical features of shigellosis occurring among cohorts of Israeli recruits followed-up for 3-6 months during the summer field training of years 1993-1997 were studied. The incidence rate of culture-proven shigellosis was the highest (78 cases per 1,000 recruits) in 1996 and the lowest (13 cases per 1,000 recruits) in 1995. Shigella sonnei (152 isolates) and Shigella flexneri (151 isolates) were the most common species. Fifty percent of the patients with shigellosis had fever (>37.5 degrees C), compared to only 18% of the subjects with other diarrheal diseases (P < 0.001). The duration of illness was longer among subjects with shigellosis than among those with other diarrheal diseases (P < 0.001). Illness due to Shigella flexneri was more severe than illness caused by Shigella sonnei.

Cryptosporidium infection in Bedouin infants assessed by prospective evaluation of anticryptosporidial antibodies and stool examination

An enzyme-linked immunosorbent assay system using oocyst lysate as antigen was used to detect serum- specific antibody responses to Cryptosporidium parvum between 1989 and 1994 in consecutive sera obtained at birth, and at the age of 6, 12, and 23 months, from 52 infants living in a Bedouin town located in the south of Israel. The serologic tests revealed high levels of immunoglobulin G anti-Cryptosporidium at birth that dropped significantly by the age of 6 months and then rose continuously to a geometric mean titer of 481 at age 23 months. The serum immunoglobulin M Cryptosporidium antibodies rose continuously from nearly undetectable levels at birth to a geometric mean titer of 471 (157-fold increase) at age 23 months. All the subjects already showed at 6 months a significant rise in immunoglobulin M. A significant rise in immunoglobulin A titers was detected in 48% and 91% of subjects at 6 and 23 months, respectively. By monthly surveillance, microscopy using the modified Ziehl-Neelsen method and confirmed by indirect immunofluorescence assay detected Cryptosporidium antigens in only 11% at age 6 months and 48% at age 23 months. The extent of exposure to Cryptosporidium immediately after birth as detected by serology is much higher than that predicted by frequent prospective assessment of stool samples.

Safety and immunogenicity of two different lots of the oral, killed enterotoxigenic escherichia coli-cholera toxin B subunit vaccine in Israeli young adults

Enterotoxigenic Escherichia coli (ETEC) is one of the leading causes of diarrhea among Israeli soldiers serving in field units. Two double-blind placebo-controlled, randomized trials were performed among 155 healthy volunteers to evaluate the safety and immunogenicity of different lots of the oral, killed ETEC vaccine consisting of two doses of whole cells plus recombinantly produced cholera toxin B subunit (rCTB). The two doses of vaccine lot E005 and the first dose of vaccine lot E003 were well tolerated by the volunteers. However, 5 (17%) vaccinees reported an episode of vomiting a few hours after the second dose of lot E003; none of the placebo recipients reported similar symptoms. Both lots of vaccine stimulated a rate of significant antibody-secreting cell (ASC) response to CTB and to colonization factor antigen I (CFA/I) after one or two doses, ranging from 85 to 100% and from 81 to 100%, respectively. The rate of ASC response to CS2, CS4, and CS5 was slightly lower than the rate of ASC response induced to CTB, CFA/I, and CS1. The second vaccine dose enhanced the response to CTB but did not increase the frequencies or magnitude of ASC responses to the other antigens. The two lots of the ETEC vaccine induced similar rates of serum antibody responses to CTB and CFA/I which were less frequent than the ASC responses to the same antigens. Based on these safety and immunogenicity data, an efficacy study of the ETEC vaccine is under way in the Israel Defense Force.

Prevalence of antibodies to West Nile fever, sandfly fever Sicilian, and sandfly fever Naples viruses in healthy adults in Israel

BACKGROUND

The arbovirus infections West Nile fever (WNF) and sandfly fever (SFF) are both endemic in the Middle East. Despite the fact that the mosquito and sandfly vectors of these viruses are still found in Israel, SFF has not been reported since 1948, whereas outbreaks of WNF occur periodically. It is suspected that some of the cases of nonspecific febrile illnesses in Israel may in fact be either WNF or SFF.

AIM

To determine the extent of past arbovirus infections in subgroups of Israeli soldiers.

METHODS

Sera from random samples of three groups of healthy soldiers aged 18-20 (n=273), 21-30 (n=497), and 40-55 years (n=285) were examined for IgG and IgM antibodies to West Nile virus (WNV), sandfly fever Sicilian virus (SFSV), and sandfly fever Naples virus (SFNV), using an ELISA method.

RESULTS

The prevalence of antibodies increased with age for all three viruses examined, and ranged from 7.0%, 0, and 2.8%, for WNV, SFSV, AND SFNV, respectively, in soldiers aged 18-20 years, to 41.9%, 23.7%, and 30.8%, in those aged 40-55 years. The percentage of seropositives for IgG who were also IgM positive were 1.0%, 5.9%, and 3.4%, for WNV, SFSV, AND SFNV, respectively. 17.5% of the seropositives for WNV were also positive for SFSV, as compared with 5.7% among the WNV-seronegatives. Among the seropositives for WNV, 23.99% were positive for SFNV, compared with 9.1% of WNV seronegatives. 48.2% of seropositives for SFSV were positive for SFNV, as compared with 8.4% for SFSV-seronegatives. In the age agroup 40-55 years, there were significantly higher prevalence rates in those born in Israel compared with those born abroad.

CONCLUSIONS

There is still significant exposure to WNV, SFSV, and SFNV in Israel. Arborviruses are probably responsible for many cases of non-specific febrile illness in this region.

Immunity to varicella zoster virus in young Israeli adults

BACKGROUND

Chickenpox is a highly contagious childhood infection caused by varicella zoster virus, a virus of the herpes family. Although a mild and self-limiting disease in otherwise healthy children, chickenpox can be a complicated and even life-threatening disease in adults, pregnant women and immunosuppressed individuals. Among infants whose mothers had varicella during the first trimester of pregnancy, 2-3% will develop a congenital VZV syndrome that includes a combination of scarring, limb deformation, central nervous system impairment and ocular injury. In 1974, a live attenuated virus vaccine against VZV was developed in Japan and has been thoroughly tested for safety, efficacy and long-term effects. In March 1995 the vaccine was licensed in the U.S. for use in healthy children only.

OBJECTIVES

To determine the rate of immunity to VZV in young Israeli adults.

METHODS

On the assumption that a randomly picked sample of 18-year-old army recruits in Israel is representative of the general Jewish population, 900 sera samples were taken for 3 years (1985,1988,1992). The sera were analyzed for IgG to VZV with a commercial ELISA kit using microwells coated with VZV antigens.

RESULTS

A total of 98% of the samples tested positive for VZV antibodies. The difference in serologic values between the recruitment years was not statistically significant.

CONCLUSION

The majority of the Israeli population reaches adulthood already immunized against VZV, with immigrants having slightly lower immunity rates. Nonetheless, a few dozen cases of chickenpox are diagnosed in the IDF annually. These data should be taken into account when a vaccination program is devised. Should such a program be implemented, it would be interesting to repeat the serosurvey for comparison. A shift in the peak occurrence age might necessitate the administration of a booster vaccine at an older age.

Quantitative analysis of IgG class and subclass and IgA serum response to Shigella sonnei and Shigella flexneri 2a polysaccharides following vaccination with Shigella conjugate vaccines

It has been recently reported that a conjugate vaccine composed of the O-specific polysaccharide of S. sonnei bound to Pseudomonas aeruginosa recombinant exoprotein A (rEPA) conferred 74% protection against S. sonnei shigellosis. In the present study affinity purified Shigella antibodies were used as standards to quantify and characterize the serum antibody response to vaccination with Shigella sonnei or Shigella flexneri 2a polysaccharide conjugated to rEPA. The geometric mean concentrations of antibodies at the pre-vaccination stage were 3.8 microg/ml for IgG anti-S. sonnei LPS and 11.26 microg/ml for IgG anti-S. flexneri 2a LPS. Vaccination with S. sonnei-rEPA and S. flexneri 2a-rEPA induced the production of specific IgG antibodies to levels of 115.8 microg/ml and 126.5 microg/ml, respectively. The levels of specific antibodies above the pre-vaccination values persisted for at least 2 years. The IgG response to S. flexneri 2a-rEPA conjugate was almost entirely represented by the IgG2 subclass. The concentration of IgG1 anti-S. sonnei LPS was significantly higher than that of IgG2 14 days after vaccination with the homologous conjugate, but decreased to similar levels to those of IgG2 6, 12 and 24 months after immunization. Since the only difference between the S. sonnei and S. flexneri 2a conjugates lies in the different polysaccharides of the two Shigella serogroups (the protein rEPA, is identical in both cases), it follows that the different pattern of IgG subclass response is a result of the different structures of the two O-polysaccharides of S. sonnei and S. flexneri 2a.

Characterization and quantitative analysis of serum IgG class and subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide following natural Shigella infection

The IgG subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide (LPS) was examined in subjects naturally exposed to these organisms. Affinity-purified LPS antibodies obtained using a column of Shigella LPS bound to epoxy-activated Sepharose 6B were used as standards to calibrate the serum antibody response to natural Shigella infection. The geometric mean concentrations of specific IgG in sera from those not exposed to Shigella organisms were 7.9 microg/mL against S. sonnei LPS and 18.6 microg/mL against S. flexneri 2a LPS. After natural exposure to S. sonnei or S. flexneri 2a, the concentrations rose to 30.3 and 127.9 microg/mL, respectively. IgG2 was the major component in the anti-S. flexneri subclass response, while the anti-S. sonnei response was dominated by IgG1. High levels of IgG1 antibodies before exposure to organisms from either Shigella serogroup correlated with a lower risk of developing symptomatic infection.

Double-blind vaccine-controlled randomised efficacy trial of an investigational Shigella sonnei conjugate vaccine in young adults

BACKGROUND

The aim of this double-blind randomised vaccine-controlled trial was to assess the efficacy of a conjugate vaccine composed of Shigella sonnei O-specific polysaccharide bound to Pseudomonas aeruginosa recombinant exoprotein A (S sonnei-rEPA) and of an oral, live-attenuated Escherichia coli/S flexneri 2a (EcSf2a-2) hybrid vaccine among military recruits in Israel at high risk of exposure to Shigella spp. We report here our preliminary findings on the efficacy of S sonnei-rEPA; we have not documented sufficient cases to assess the efficacy of EcSf2a-2.

METHODS

Between April, 1993, and August, 1994, male Israeli Military recruits aged 18-22 years were asked to take part in our study. We enrolled 1446 soldiers from seven separate field sites (groups A-G). Soldiers were randomly allocated one injection of S sonnei-rEPA and four doses of oral placebo (n = 576), four oral doses of EcSf2a-2 and one injection of saline placebo (n = 580), or one injection of meningococcal tetravalent control vaccine and four doses of oral placebo (n = 290). Because there were no cases of S flexneri 2a, the EcSf2a-2 and meningococcal vaccines were the control group. We defined S sonnei shigellosis as diarrhoea with a positive faecal culture for S sonnei. Each group of soldiers was followed up for 2.5-7.0 months. The primary endpoint was protective efficacy of S sonnei-rEPA against S sonnei shigellosis.

FINDINGS

Cases of culture-proven S sonnei shigellosis occurred in four groups of soldiers (groups A-D), which comprised 787 volunteers (312 received S sonnei-rEPA, 316 received EcSf2a-2, and 159 received meningococcal control vaccine). In groups A-C, cases of shigellosis occurred 70-155 days after vaccination, whereas in group D cases occurred after 1-17 days. In groups A-C, the attack rate of shigellosis was 2.2% in recipients of S sonnei-rEPA compared with 8.6% in controls (protective efficacy 74% [95% CI 28-100], p = 0.006). S sonnei-rEPA also showed significant protection against shigellosis in group D (43% [4-82], p = 0.039). Prevaccination and postvaccination ELISA measurements of antibody to S sonnei lipopolysaccharide among recipients of S sonnei-rEPA showed that the vaccinees who developed S sonnei shigellosis had significantly lower serum IgG and IgA responses to the homologous lipopolysaccharide than those who did not (p = < 0.05).

INTERPRETATION

One injection of S sonnei-rEPA confers type-specific protection against S sonnei shigellosis. The high antibody concentration induced by the conjugate vaccine in volunteers who did not develop shigellosis suggests that there is an association between serum antibody titre and protection.

Measles immunity and response to revaccination of a young adult population in Israel

In order to evaluate the true immune status and the effect of revaccination on a young adult population, we collected serum samples from 289 military recruits who were vaccinated during an outbreak in 1991. Most vaccinees, age 18-25 years, had apparently been immunized once before as infants. Sera collected just prior to the vaccination and 14 and 28 days afterwards were tested for measles antibodies by hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA)-IgM. Before vaccination, 46 (15.9%) of the subjects had no HI antibodies, (< 1:4) and 48 (16.6%) had borderline (1:4) HI titer. Following vaccination, only ten (3.5%) remained negative and 19 (6.6%) had borderline titer. The increase in HI antibody titer was inversely proportional to the prevaccination titer, and 159 subjects (55.0%) showed no increase at all. The geometric mean titer (GMT) rose from 9.14 to 21.47. Among the prevaccination-negative subjects (HI < 1:4) 28 (60.9%) reached a postvaccination titer of > or = 1:8, and eight (17.4%) reached a titer of 1:4. Twelve (26.1%) of the negative subjects seroconverted and developed IgM, 16 (35%) seroconverted without IgM, and 18 (39%) remained negative and did not develop IgM. A group of eight vaccinees with prevaccination titer of > or = 1:4 developed IgM. Some were probably infected by the circulating wild-type virus prior to the vaccination. Thus, a total number of 20 of the 289 subjects studied (6.9%) had true negative preimmune status as judged by the IgM test. However, the vaccination campaign prevented further measles cases, apparently by increasing the population's immunity, particularly in individuals with very low titers or without measles antibodies.

Determination of immunity to measles virus in young adults: comparative evaluation of a commercial enzyme immunoassay and the hemagglutination inhibition techniques

BACKGROUND

Determination of the immune status against measles in young adults requires careful evaluation of the laboratory methods because of waning immunity. The hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) may lack the sensitivity required to detect very low levels of antibodies. In addition, the correlation between ELISA-IgG assays and the degree of protection from measles is not well defined.

OBJECTIVES

(a) Evaluation of a commonly used measles ELISA-IgG test kit in comparison with the hemagglutination inhibition (HI) test which corresponds strongly to virus neutralization; (b) determination of false negative rates of the ELISA-IgG and the HI tests; (c) evaluation of the ELISA-IgG test kit as a quantitative assay.

STUDY DESIGN

One hundred and eighty serum samples collected from 60 vaccinated young adults immediately before vaccination and 14 and 28 days postvaccination, were tested comparatively by HI and by a commercial ELISA-IgG kit. For evaluation of false negative rates, postvaccination sera of a cohort of 48 vaccinees with negative HI or ELISA-IgG prevaccination sera were tested for IgM. Sixty-three of the samples were also titrated by the ELISA-IgG kit using serial dilutions, for comparison with HI titers.

RESULTS

Using the HI test as a reference method, the ELISA-IgG kit was found to have overall accuracy of 81%, sensitivity of 80% and specificity of 84%. The false negative and the false positive rates were 20% and 16%, respectively. In contrast, when we used postvaccination IgM test to distinguish between true and false prevaccination negatives in both the HI and ELISA-IgG tests, we found that the false negative rates were 75.6% by ELISA and 72.5% by HI, and false positive rates were 2.4% and 0%, respectively. Serum titers determined by the ELISA-IgG test were generally 5-10-fold higher than the corresponding HI titers, but without a consistent correlation.

CONCLUSIONS

Both the ELISA-IgG and the HI tests frequently failed to detect residual immunity. The two tests also did not correlate well with each other suggesting that different antigenic determinants of the virus are involved in each assay and therefore the HI test should not be used as a reference method for evaluation of the sensitivity of ELISA IgG kits.

Safety and immunogenicity of investigational Shigella conjugate vaccines in Israeli volunteers

The safety and immunogenicity of investigational conjugates, composed of the O-specific polysaccharides of Shigella sonnei and Shigella flexneri type 2a covalently bound to Pseudomonas aeruginosa recombinant exoprotein A (rEPA), were evaluated in 192 Israeli soldiers. None had significant local reactions or fever. Fourteen days after injection, 90% of S. sonnei-rEPA recipients and 73 to 77% of S. flexneri-rEPA recipients had a fourfold or greater increase in serum immunoglobulin G (IgG) and IgA anti-lipopolysaccharide (anti-LPS) levels; at 2 years, these remained higher than at prevaccination (P < 0.01). There was a fourfold or greater increase in IgM anti-LPS in 20% of vaccinees at 2 weeks, but levels returned to prevaccination values at 6 to 12 months. IgG was the highest and most sustained class of LPS antibodies. Reinjection at day 42 did not boost antibody levels. Eighteen of 23 (78%) who received S. sonnei-rEPA and 13 of 19 (68%) who received S. flexneri-rEPA. had significant IgA-secreting cell responses. Significant IgG antibody-secreting cell responses were detected in 19 of 23 (83%) and 11 of 19 (58%) volunteers following vaccination with S. sonnei-rEPA and S. flexneri 2a-rEPA, respectively. On the basis of these data, further evaluation of the Shigella conjugates for protective efficacy in field trials in Israel was started.

Detection of antibodies to Shigella lipopolysaccharide in urine after natural Shigella infection or vaccination

The purpose of the present study was to explore the possibility of detecting antibodies to Shigella sonnei lipopolysaccharide (LPS) in urine after infection or vaccination. Urinary immunoglobulin A (IgA) and IgG antibodies and specific IgA secretory protein against S. sonnei LPS were measured by enzyme-linked immunosorbent assay (ELISA), after adjustment for urine concentration. A significant antibody level was defined as one above a cutoff value calculated from the geometric mean + 2 standard deviations of urinary anti-S. sonnei LPS levels in 43 healthy hepatitis B vaccinees (controls). Of 11 culture-proven cases of S. sonnei shigellosis, at convalescence 9 (82%) had significantly elevated levels of urinary antibodies to the homologous LPS. The S. sonnei conjugate vaccine, composed of S. sonnei O-specific polysaccharide covalently bound to recombinant exoprotein A of Pseudomonas aeruginosa, elicited a significant urine IgA or IgG anti-LPS response in 60% (6 of 10), 56% (9 of 16) 43% (16 of 37), and 14% (3 of 21) of the volunteers at 2 weeks, 6 weeks, 6 months, and 12 months after vaccination, respectively. The specificity of the urine antibody response to S. sonnei LPS was documented by the total lack of response in subjects who received parenteral Shigella flexneri 2a-recombinant exoprotein A conjugate (69 urine samples) or meningoccal tetravalent control vaccines (4 urine samples). All the volunteers who lacked a significant response to S. sonnei LPS in serum also lacked such response in urine samples. Seventy-four percent of the volunteers with a significant IgA or IgG anti-LPS response in serum at convalescence or 14 days after vaccination showed a similar response in urine. The ratio of the titer of secretory protein bound to IgA anti-S. sonnei LPS in urine to that in serum was 303 times higher than the ratio of anti-S. sonnei LPS total IgA titer in urine to that in serum, indicating that the urine IgA is of secretory origin. These findings suggest the possible use of urinary Shigella LPS antibodies as markers of systemic and secretory immune responses after natural infection or vaccination. At this stage, because of its limited sensitivity, the detection by ELISA of Shigella LPS antibodies in urine cannot replace the same assay in serum as a definitive test in an individual with a negative result.

Ethnic differences in the prevalence of anti-hepatitis C antibodies and hepatitis B surface antigen in Israeli blood donors by age, sex, country of birth and origin

The presence of anti-hepatitis C virus (HCV) antibodies frequently indicates both persistent infection and infectivity. Consequently, blood donors found to be anti-HCV positive, are excluded from the donor pool. The aim of this study was to compare age, sex and ethnic differences in the prevalence of anti-HCV antibodies with that of hepatitis B surface antigen (HBsAg) among immigrant and Israeli-born blood donors. Anti-HCV antibodies were assayed by a second-generation enzyme-immunoassay (EIA) and HBsAg by a standard EIA in a sample of 136,977 blood donors in Israel during 1992. The overall age-adjusted prevalence of anti-HCV antibodies was 0.66% in men and 0.55% in women, and for HBsAg, 0.85% and 0.44%, respectively. There was a significant increase in the prevalence of anti-HCV antibody with age, and significant differences by country of birth, with the highest prevalence found among those born in the former USSR and eastern Europe. This contrasted with the findings for the prevalence of HBsAg, where the highest rates were among those born in northern Africa. Among Israeli-born donors, differences in the prevalence of anti-HCV antibodies by parental country of origin were minimal and much less than for HBsAg. Hence the prevalence of anti-HCV antibodies in Israel is strongly associated with age and country of birth but not with country of origin. There is little evidence of substantial vertical or intrafamilial transmission of HCV infection in Israel.

Safety and immunogenicity of the oral E. coli K12-S. flexneri 2a vaccine (EcSf2a-2) among Israeli soldiers

A double-blind placebo-controlled study was carried out on the safety and immunogenicity of the oral Shigella flexneri (EcSf2a-2) vaccine among Israeli soldiers. Sixty volunteers received the vaccine and 59 received placebo. Fifty-three were given the full vaccine regimen (four doses). Doses ranged between 4.1 x 10(8) and 1.1 x 10(9) c.f.u. Visits to the unit clinic for mild gastrointestinal symptoms were common after the first dose in vaccinees (13%) as compared with placebo recipients (5%), but the difference was not significant, p = 0.12. Similarly, there was no difference between the groups for either gastrointestinal or non-gastrointestinal complaints reported by questionnaire. The vaccine strain was excreted by 69% and 67% of the vaccinees one day after receiving the second and the fourth doses, respectively. As judged by antibiotic susceptibility, phage typing and restriction fragment length polymorphism (RFLP), the vaccine strain emerged as genetically stable after replication in human gut and shedding. There was neither bacteriological nor serological evidence of transmission of the vaccine from vaccinees to placebo recipients. Eighteen of 26 (69.2%) and 11 of 30 (36.7%) vaccinees had significant IgA secreting cell responses 7 and 21 days after the first dose, respectively. Significant IgA or IgG serum antibody response to S. flexneri 2a LPS was detected in 30% of the vaccinees. These results support further evaluation of EcSf2a-2 vaccine protective efficacy in field studies.

Incidence of diabetes mellitus in various population groups in Israel (1989 and 1990)

A prospective survey of all newly diagnosed insulin-dependent diabetes mellitus (IDDM) children and adolescents aged 0-17 years in Israel was conducted for the years 1989 and 1990. All diabetic clinics in Israel treating young diabetics were contacted and they returned written reports to us. Each clinic was also visited regularly by a member of the team who reviewed the individual charts to obtain data on population origin as well as medical and demographic data. A total of 187 patients were identified (164 Jews and 23 Arabs), giving a total incidence rate of 5.46/10(5). Analysis of the incidence rates by population groups showed that Arabs and Jews originating in Asia had the lowest incidence (2.77 and 4.58/10(5) respectively), followed by Jews whose fathers were born in Israel (5.61/10(5)). The highest incidence was registered for Jews originating from Europe and North America (9.34/10(5)). The female-to-male preponderance ratio was higher in the Jews originating in Asia (2.1) than in Jews originating in Europe and North America (1.2). Comparing the present data with a survey performed for the years 1975-80 we found a statistically significant increase in incidence in all population groups. Our findings strongly suggest an influence of genetic factors on the incidence of childhood IDDM.

Sex differences in the humoral antibody response to live measles vaccine in young adults

BACKGROUND

Following vaccination of children using high-titre live measles vaccine, excess non-specific mortality was reported, particularly among females. Since vaccination with live measles virus results in a temporary depression of the immune response to other antigens, the female predominance in subsequent non-measles mortality may be due to sex differences in response to live measles vaccines.

METHODS

In this study, the immunogenicity of standard titre live Schwarz strain measles vaccine was examined 2 and 4 weeks post-vaccination in 223 males and 66 female aged 18-20 years in Israel in 1991.

RESULTS

Females had higher post-vaccination geometric mean titre (GMT) at all levels of pre-vaccination titres at both 2 and 4 weeks. Furthermore, after controlling for differences in pre-vaccination titres, overall the post-vaccination GMT for females was about 50% higher than for males (P < 0.001).

CONCLUSIONS

These findings indicate that females exhibit a stronger humoral immune response to measles vaccine. Possible sex differences in immunosuppression following measles vaccination should be explored.

Long-term persistence of anti-diphtheria toxin antibodies among adults in Israel. Implications for vaccine policy

Vaccination against diphtheria has essentially led to the disappearance of the disease in Israel. However, in other countries with high immunization coverage, isolated cases and small outbreaks have occurred in adults. Immunity following vaccination or natural exposure to toxigenic strains of C. diphtheriae is conferred by serum antibodies to diphtheria toxin. Since booster doses of diphtheria toxoid are recommended every ten years in adults, this raises the question of persistence of protective levels of anti-diphtheria toxin antibodies. In this study we assessed a possible age-related decline in anti-diphtheria toxin antibodies among adults in Israel. The study population comprised random samples in three age groups: 263 male recruits aged 18-19 years, 116 male reserve soldiers aged 25-35 years and 153 aged 41-51 years. Anti-diphtheria toxin antibody levels were measured by means of ELISA. Results indicate that 64.3% (95% CI = 58.5-70.1%) of those aged 18-19 had anti-diphtheria toxin levels in excess of 0.1 IU ml-1, whereas the corresponding figures for ages 25-35 and 41-51 were 32.8% (95% CI = 24.2-41.3%) and 15% (95% CI = 9.4-20.7%). However, even in the oldest age group, 95.4% (95% CI = 90.8-98.1%) had antibodies above the presumed protective level of 0.01 IU ml-1. Although these results indicate a significant age-related decline in anti-diphtheria toxin antibodies in vaccinated subjects, most had apparently protective levels. The absence of cases suggests that vaccine-induced immunity is long-lasting. However the immune status of the population should be carefully monitored.

Four-year follow-up of the immune status of young adults given a single booster dose of trivalent oral poliovaccine

In 1988 an outbreak of type 1 paralytic poliomyelitis occurred in Israel. Almost the entire population in the age group 0-40 years received a single dose of trivalent oral polio vaccine. We examined the serological responses to the vaccine at 2 weeks and 4 years later, in a group of 17 vaccines. Geometric mean antibody titres (GMTs) against both the type 1 epidemic and Mahoney strains had declined by about 50% from the levels found at 2 weeks after vaccination. However, they were still more than five times higher than the prevaccination levels. All vaccines had neutralizing antibody titres against both the type 1 strains of at least 1:64, well above the 1:8 titre regarded as protective. The GMTs against the type 2 and 3 strains declined to about one-third of the 2-week postvaccination levels but were also well above protective levels. These findings indicate that antibody titres against both the Mahoney and epidemic type 1 strains remained at very adequate levels over a period of at least 4 years. Thus the immunity resulting from a single booster dose of oral poliovaccine in young adults is likely to be long-lasting, a finding of particular importance for travellers on extended visits to endemic areas.

A trial of the reactogenicity and immunogenicity of an inactivated hepatitis A vaccine

Purified, formaldehyde-inactivated and alum-adjuvanted hepatitis A virus (HAV) vaccines have recently become available for clinical trials. The vaccine is administered intramuscularly in a schedule of 0, 1, and 6 months. The aim of the study was to evaluate the reactogenicity and immunogenicity of an inactivated hepatitis A (HA) vaccine. Three groups of volunteers comprised the study population: 28 volunteers without antibody to HAV were given HA vaccine and, for comparison, 43 subjects received hepatitis B vaccine for possible adverse reactions to the HA vaccine; 12 other subjects received immunoglobulin alone. Each 1 ml dose of HA vaccine contained 720 enzyme units or about 100 ng of antigen. Anti-HAV was determined by means of a commercial assay (Abbott Laboratories: HAV-EIA), and by a more sensitive ELISA. No significant adverse reactions were reported. In the group that received HA vaccine, 4 weeks following the first dose all had detectable antibodies (> or = 20 mIU/ml) by the sensitive ELISA. By commercial HAV-EIA, at 20 weeks following the second dose 75.0% had detectable antibodies, and after the third vaccine all had detectable antibodies. This new inactivated HA vaccine is highly immunogenic and had no significant side effects.

Clinical, serological and molecular characteristics of 471 hepatitis B virus carriers

A total of 471 Israel Defense Forces (IDF) blood donors identified as hepatitis B virus (HBV) carriers were examined a few months after blood donation. When compared to the general population of IDF blood donors the HBV carriers were older, belonged to certain ethnic groups and were predominantly males. Physical examination revealed minimal findings: 1 (0.3%) had splenomegaly and 5 (1.6%) had hepatomegaly. Fifty-two individuals (11.1%) had elevated liver enzymes. E antigen was present in 3.2% of HBV carriers, 94% had anti-e antibodies and 1.9% had anti-delta antibodies. Of 258 carriers tested for HBV DNA, 29 (11.2%) were positive. Abnormal liver enzymes were significantly associated with the presence of e antigen as well as with the presence of HBV DNA.

Epidemiology of acute diarrheal diseases in children in a high standard of living rural settlement in Israel

Epidemiologic patterns of acute diarrheal diseases in a high standard of living communal settlement, situated in a region endemic for enteric diseases, were evaluated by a historical prospective study of 284 children (12,064 child months) from August, 1988, through July, 1992. Three hundred eighty-three episodes of acute diarrhea were identified, yielding a rate of 0.38 episode per 12 child months. One hundred and children (35.6%) were reported to have 1 to 4 diarrheal episodes and 29 (10.2%) children had 5 or more diarrheal episodes during the follow-up period. The mean number of episodes of acute diarrhea per 12 child months in children ages 0 to 2 years was 2.28, in 2- to 6-year-olds 0.44, in 6- to 13-year-olds 0.12 and in 13- to 18-year-olds 0.03 (P < 0.001). Children less than 12 months of age had a lower incidence of acute diarrheal diseases during the months they were being breast-fed than children that were fed with formula during the same period (1.22 vs. 3.06 episodes per 12 child months, respectively; P < 0.001). Enteropathogens were isolated in 40% of diarrheal episodes in which stool cultures were obtained. The identification rates of the various enteropathogens were: diarrheagenic Escherichia coli, 11%; Shigella spp., 10%; Giardia lamblia, 10%; Salmonella spp., 4%; Staphylococcus aureus, 3%; Campylobacter jejuni, 1%. Potential interventions against acute diarrhea in this set up of a high standard of living rural community are education of caretakers and parents on hygienic practices that can prevent transmission of pathogens among the young children and encouraging mothers to breast-feed their children.

Depression of the immune response to an inactivated hepatitis A vaccine administered concomitantly with immune globulin

Inactivated hepatitis A virus (HAV) vaccine is given in a three-dose schedule. When rapid protection is needed, injection of immune globulin (IG) concomitantly with the first dose could provide passive protection until adequate active antibody response has developed. A possible effect of IG on the immune response to the vaccine was studied in healthy volunteers; 28 received vaccine alone, and 34 received the first dose simultaneously with 5 mL of IG. A control group received hepatitis B vaccine, and a fourth group received IG alone. Four weeks after the first vaccine dose, all subjects had detectable ELISA anti-HAV antibodies. Several weeks after each vaccine dose, the geometric mean titer of antibodies was significantly lower in those who received vaccine with IG but higher than in those who received IG alone. Results for neutralizing antibodies yielded a similar trend. If IG is given with HAV vaccine, a further booster vaccine dose may be required to ensure long-lasting immunity.

Ethnic and gender differences in the prevalence of anti-cytomegalovirus antibodies among young adults in Israel

The population of Israel comprises offspring of immigrants from countries of high and low incidence of cytomegalovirus infection. To evaluate possible ethnic differences in the prevalence of antibodies against cytomegalovirus in young adults, blood samples were taken from a random sample of 422 Israel military recruits aged 18-19 years, during 1987. Antibodies against cytomegalovirus were determined by means of ELISA. Subjects originating from North Africa or Asia had higher prevalences than those originating from Western countries (84.0% and 74.0% versus 60.0%, P < 0.001) and the differences persisted after adjustment for gender, education and socioeconomic status. The prevalence of antibodies was significantly lower in men than in women (63.1% versus 76.5%). These findings identify subpopulations who are at increased risk of primary cytomegalovirus infection during adulthood and may be candidates for future anti-cytomegalovirus vaccines.

Immunity to measles in young adults in Israel

The likelihood of an epidemic of measles in 1990-92 in Israel prompted us to study the immune status against measles in a random sample of 454 recruits aged 18-19 years in order to obtain data that might be used in determining vaccination policy. This cohort had received one dose of measles vaccine at 12 months of age. The measles immunity status was studied by determination of antibody values that were measured by means of an enzyme-linked immunosorbent (ELISA) IgG antibody test. Of the recruits, 84.6% were found to have positive sera for anti-measles IgG antibodies, while 13.7% had negative sera. Eight (1.7%) subjects had borderline results. The results of this study indicate the need to administer a second dose of measles vaccine at an older age in addition to the MMR (measles, mumps, rubella) vaccine that is now given in Israel at 12 months of age. This step will help achieve the World Health Organization's target of complete eradication of measles.

Drug use among Israeli army personnel: an epidemiological study

A survey of drug use among Israeli army personnel was conducted as part of a national survey of drug use initiated by the Anti Drug Authority of Israel during 1990. One thousand one hundred and twenty-five male and female soldiers from various units and ranks were selected by the use of randomized cluster sampling. Seventy to eighty-five per cent of the soldiers presented negative attitudes towards the use of illicit drugs and its users. Only 67 (6.1%) soldiers reported the use of some illicit drugs in the last 30 days; half of them started to use drugs before the age of 18. The main reported use was of hashish, marijuana and tranquillizers. The use of opium, heroin, cocaine was rarely reported. The use of cigarettes and alcohol within the last 30 days was much higher and was reported by 44.6% and 69.0% of the soldiers, respectively. Using multiple logistic regression analysis it was shown that illicit drug use in the last 30 days was significantly associated with higher number of individuals per household, less satisfaction with military service, and positive attitudes towards the use of drugs. The results of the present study, along with a comparison with different populations that were surveyed parallel to our research indicate that military service in the Israel Defence Force (IDF) is not associated with significant use of illicit drugs. Our results indicate the need for more attention to alcohol and cigarette use among army personnel.

Age differences in immunity against wild and vaccine strains of poliovirus prior to the 1988 outbreak in Israel and response to booster immunization

During the 1988 type 1 polio outbreak in Israel, most cases occurred in previously vaccinated subjects aged 11-30 years, suggesting a possible age-related immunity deficit against the wild virus responsible for the outbreak. We examined type 1 poliovirus neutralizing antibody titres against the Sabin strain, the standard wild strain (Mahoney), the wild strain responsible for the 1988 outbreak and a previous wild strain from the region, on frozen sera drawn prior to the mass vaccination campaign from subjects aged 6 to 40 years. Response to vaccination with oral poliovaccine (OPV) was examined in a subgroup aged 18-40 years. At all ages, the highest antibody titres prior to the outbreak were against the Sabin strain. Geometric mean titres (GMTs) against both the Sabin strain and the wild Mahoney strain were significantly higher in the age groups 6-7, 12-13 and 30-40 years compared with the 18-29-year-olds. For the other wild strains, the GMT for those aged 30-40 years was significantly and substantially higher than in the other age groups, followed by the 12-13- and 6-7-year-olds and lowest in those aged 18-29 years. Following vaccination with OPV in subgroups aged 18-29 and 30-40 years, GMTs against Sabin and all wild strains were similar to each other and in both age groups. These findings suggest that there was a relative immunity gap against the wild type 1 strains in the age group that lacked prior exposure to wild virus and had received the last OPV dose more than 17 years previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Sociodemographic factors and the declining prevalence of anti-hepatitis A antibodies in young adults in Israel: implications for the new hepatitis A vaccines

In order to examine changes in the epidemiology of hepatitis A virus (HAV) infection in Israel during the past decade, a sero-epidemiological study was carried out in 1989 in a random sample of 1153 members of the permanent army, aged 21-30 years. Of the males 59.2%, and 54.3% of the females were anti-HAV antibody positive (p = 0.22). At all ages, the highest prevalence was in those of North African origin, followed by those of Asian, native Israeli and Western origin. There was a marked decline in the prevalence of antibodies in later birth cohorts, (from 74.4% in those born in 1959-1960, to 47.8% in those born in 1967-1968). Age, ethnic origin, number of siblings, more than two younger siblings and smoking were independently significantly associated with anti-HAV antibodies. Despite an overall decline in family size in later birth cohorts, ethnic differences remain prominent. These findings suggest that when the new active hepatitis A vaccines become available, their use in small children should dramatically reduce the incidence of diseases in highly endemic areas by limiting intrafamilial spread of the disease.

Prevalence and correlates of diphtheria toxin antibodies among young adults in Israel

The paucity of information about immunity against diphtheria of young adults in Israel prompted us to analyse sera from a random sample of 480 recruits (263 males and 217 females) aged 18-19 years. Antitoxin antibody levels were determined by means of ELISA. Of the recruits 58.1% had antibody values greater than 0.1 IU/ml; 38.5% had amounts between 0.01 and 0.1 IU/ml, which is considered low when using the ELISA method, and 3.3% had less than 0.01 IU/ml. The results of this study suggest that a booster dose of antidiphtheria vaccine should be given to adults in Israel in order to ensure adequate antibody levels.

Sociodemographic factors associated with serum anti-Shigella lipopolysaccharide antibodies and shigellosis

The association between various sociodemographic variables and the presence of anti-Shigella sonnei lipopolysaccharide (LPS) antibodies was examined in a random sample (N = 383) of male Israeli conscripts. Of the male conscripts, 190 (49.6%) had pre-existing antibodies against S. sonnei LPS (defined as HA titres of greater than or equal to 1:10 after treatment of sera with 2-mercaptoethanol). Univariate analysis revealed a significant positive association between the presence of humoral anti-S. sonnei LPS antibodies and sociodemographic variables including Eastern origin (p = 0.007), low socioeconomic status (p = 0.0016), and the number of siblings (p = 0.023). When multiple logistic regression was used to control simultaneously for the effects of the other variables, ethnic origin emerged as the strongest correlate of anti-S. sonnei LPS antibodies. On the other hand, the association of the sociodemographic variables in subjects suffering from S. sonnei infection during their military service, was in the opposite direction (p less than 0.001 for both socioeconomic status and ethnicity). These findings suggest differences between subpopulations in acquired immunity to S. sonnei due to differences in exposure to the homologous organism prior to military service.

Reduction of transmission of shigellosis by control of houseflies (Musca domestica)

The effect of control of houseflies on the incidence of diarrhoea and shigellosis was evaluated in a prospective crossover intervention study at two military field bases several kilometers apart. In early summer, 1988, intensive fly control measures (mainly bait and trap strategy) were introduced on one base, while the other served as a control. After 11 weeks, as new cohorts arrived, the intervention was abruptly discontinued in the first base and instituted in the second for the next 11 weeks. The study was repeated the next summer. Overall, fly counts were 64% lower on the bases exposed to fly control measures (p = 0.024). Concomitantly, clinic visits dropped by 42% (p = 0.146) for diarrhoeal diseases and by 85% for shigellosis (p = 0.015), as did rates of seroconversion, by 76% (p = 0.024) for antibodies to Shigella and by 57% (p = 0.006) for antibodies to enterotoxigenic Escherichia coli. The findings indicate that houseflies, acting as mechanical vectors, transmit Shigella (and possibly enterotoxigenic E coli) diarrhoeal infections.

Ethnic differences in the prevalence of hepatitis B surface antigen among Israeli blood donors: changes between 1972 and 1988

The prevalence of hepatitis B surface antigen (HBsAg) carriers among blood donors in Israel during 1988 was compared with that in a similar survey carried out on donors during 1972. The overall age- and sex-standardized prevalence of HBsAg declined from 1.22% to 1.01%. The ethnic differences previously observed were much diminished in native Israelis. The age of highest prevalence shifted from 18-21 to 31-40 years of age, probably due to a cohort effect. The higher prevalence among males has persisted. These findings indicate that the strong ethnic differences in the prevalence of HBsAg previously observed in Israel probably reflect the high rate of infections in the country of birth, and although intra-family spread may have persisted, the overall infection rate in Israel is much lower.

Prospective study of the association between serum antibodies to lipopolysaccharide O antigen and the attack rate of shigellosis

A means for determining immune status against shigellosis would significantly improve the design and evaluation of interventional and other epidemiologic studies. Previous case-control studies have indicated the potential role of humoral antilipopolysaccharide antibodies. To test this proposition, 190 soldiers serving in a field unit were monitored prospectively for 2.5 months for shigellosis. Blood samples were taken at the beginning of the follow-up period and tested for serological evidence of prior exposure to Shigella sonnei and Shigella flexneri. The risk for acquiring S. sonnei shigellosis was 3.7 times higher for individuals lacking homologous antibodies (P less than 0.02). The risk for acquiring S. flexneri shigellosis was 2.4 times higher for individuals lacking antibodies, although a low attack rate for S. flexneri resulted in numbers too small to achieve statistical significance. While the importance of the serum antilipopolysaccharide antibodies in protection against the disease remains unclear, these findings demonstrate that they are strong markers of acquired immunity. Serological markers should be incorporated in epidemiologic studies of shigellosis and in the design and evaluation of future trials of potential anti-Shigella vaccines.

Mumps vaccination of young adults is unwarranted

A clinical and epidemiological study of mumps was carried out over a 18-month period and included 104 soldiers (61% of the reported cases in the Israel Defence Forces). The average number of days off work was 12.9 +/- 9.2 days. The most common complication was orchitis (19/72 men; 26%), followed by 3 cases of pancreatitis (3%) and 2 cases of meningitis (2%). 13 men with orchitis were tested, and all had normal spermograms. No long term important sequelae were described. The transmission rate was low with no respondent reporting more than one secondary case among soldiers serving in the same unit. The socio-economic level of mumps patients was comparable to that of the general army population at the time of the study. Our data do not support a mass immunization program of the adult population.

Sociodemographic correlates of neutralizing poliovirus and hepatitis A virus antibodies as markers of different modes of acquiring immunity

The prevalence and sociodemographic correlates of antibodies against poliovirus and hepatitis A virus (HAV) were compared in a random sample of 457 military recruits in Israel inducted during 1987. Lower socioeconomic status (SES) was associated with a higher prevalence of anti-HAV antibodies (67.3 vs 32.5 percent), whereas the reverse was true for type 1 poliovirus (78.4 vs 89.5 percent). While the high prevalence of anti-HAV antibodies observed in the lower SES groups reflects considerable natural exposure to enteroviruses, immunity against poliovirus appears to be determined primarily by compliance with vaccination.

Response to trivalent oral poliovirus vaccine with and without immune serum globulin in young adults in Israel in 1988

Fifteen cases of type 1 paralytic poliomyelitis occurred in August 1988, mainly among young adults in the Jewish population of Israel, where vaccine coverage exceeds 90%. The military forces, as a precaution against further spread of the virus, vaccinated all recruits in late September. They received oral poliovirus vaccine (OPV) simultaneously with prophylactic immune serum globulin (ISG) to protect against hepatitis A virus infection. Since it is generally not recommended to administer live vaccines simultaneously with ISG, the serologic response to OPV given at the same time as ISG was compared with the response when OPV was given alone; specimens were also available from a control group receiving ISG alone. No effect of ISG on the antibody response to OPV was found, and thus there appears to be no contraindication to giving OPV at the same time as injecting pooled ISG--particularly relevant for travelers to areas endemic for both diseases, who have to leave at short notice. Of recruits 18-19 years of age, 21% lacked antibodies to type 1 poliovirus, suggesting either a decline in antibody titers with age or a lack of vaccine potency during earlier years. After the booster, only 2% lacked type 1 antibody, and the geometric mean titer increased from 1:16 to 1:698.

Seasonality and long-term trends of pediculosis capitis and pubis in a young adult population

Little is known about seasonality and long-term trends in the incidence of pediculoses. Such information would help both public health workers and clinicians in the prevention and management of the problem. In the Israel Defence Forces the pediculoses are individually notifiable, and this provides a unique database for the study of this subject. The incidence of head louse infestation increased from 5.2 per 1000 in 1977 to 18.1 per 1000 in 1979, and then declined to 3.6 per 1000 in 1987. The incidence was higher in the warmer months. Pubic louse infestation increased from 7 per 1000 in 1977 to 14.9 per 1000 in 1983, and then declined to 4.6 per 1000 in 1987. The incidence was higher in the cooler months. Possible causes of the seasonality and long-term trends are discussed.