The seroepidemiology of rubella in western Europe

Most of the countries in western Europe have now implemented mass infant rubella immunization programmes, instead of or in addition to selective vaccination in order to achieve the elimination of congenital rubella syndrome. The European countries Denmark, England and Wales, Finland, France, Germany, Italy and the Netherlands undertook large, national serological surveys collecting several thousand serum specimens during 1994-8. Antibodies against rubella virus were detected by a variety of enzyme immuno-assays. Comparability of the assay results was achieved by a standardized methodology. The age- and sex-stratified serological results were related to the schedules, coverage of rubella vaccination and the incidence in these countries. The results show widely differing levels of immunity to rubella both in the general population and in the specific age groups of males and females. A low rate (< 5%) of susceptibles in childhood and adolescents of both sexes was obtained only in Finland and the Netherlands. Countries such as Italy with only moderate coverage for the infant immunization programme currently have both high susceptibility levels in the general population and in the at-risk population. The likelihood is of continued epidemics of rubella with cases of congenital rubella syndrome. The continued implementation of selective vaccination will help to offset the impact of this ongoing transmission and to protect women on reaching childbearing age.

The sero-epidemiology of diphtheria in Western Europe. ESEN Project. European Sero-Epidemiology Network

Seven countries in Western Europe collected large, representative serum banks across the entire age range and tested them for diphtheria anti-toxin (sample size ranged from 2991 to 7715). Although a variety of assays were used, the results were all standardized to those of a reference laboratory and expressed in international units. The standardization process, and the availability of similar, large data sets allowed comparative analyses to be performed in which a high degree of confidence could be ascribed to observed epidemiological differences. The results showed that there were large differences in the proportion of adults with insufficient levels of protection amongst different countries. For instance, roughly 35% of 50- to 60-year-olds were found to be seronegative (titre < or = 0.01 IU/ml) in Finland compared with 70-75% in the United Kingdom. Furthermore, the proportion of seronegative adults would be expected to increase in some countries, notably Italy and the western part of Germany. In those countries with vaccination of military recruits there was a marked sex-related difference in the proportion of seropositive individuals. All countries have high levels of infant vaccine coverage (> 90%) but the accelerated schedule in the United Kingdom appears to result in lower anti-toxin titres than elsewhere. In Sweden, booster doses are not offered until 10 years of age which results in large numbers of children with inadequate levels of protection. Although the United Kingdom and Sweden both have higher proportions of seronegative children than elsewhere the likelihood of a resurgence of diphtheria in these countries seems remote.

Diphtheria antibody levels in the Italian Population

Immunity to diphtheria was assessed in serum samples obtained from 3111 healthy Italian males and females aged 0-84 years. Diphtheria antitoxin was tested using a double-antigen, time-resolved fluorescence immunoassay (DA-DELFIA). According to internationally accepted criteria, antitoxin concentrations < 0.01 IU/ml indicate susceptibility to diphtheria, those > or = 0.01-0.09 IU/ml provide basic or inadequate protection, and concentrations > or =0.1 IU/ml are protective. By these criteria, 9.9% (95% CI 8.9 to 11.18) of the participants were susceptible to diphtheria, 30.2% (95% CI, 28.6 to 31.9) had basic protection, and 59.9% (95% CI, 58.1 to 61.6) were protected. The prevalence of unprotected individuals showed an age-related increase, up to the 45-49-year-old age group for females and the 50-54-year-old age group for males (34.9% and 31.3% of individuals, respectively). The prevalence of immunity did not significantly differ in relation to sex in any of the age groups. These results indicate that booster shots should be routinely provided to the adult population in order to maintain a protective level of diphtheria antibodies.

Cell-mediated immunity and antibody responses to Bordetella pertussis antigens in children with a history of pertussis infection and in recipients of an acellular pertussis vaccine

Cell-mediated immunity (CMI) and antibody responses to Bordetella pertussis antigens were assessed 4-6 years after primary infant immunization with diphtheria-tetanus tricomponent acellular pertussis (DTaP) or diphtheria-tetanus (DT) vaccine in a country with high endemicity of B. pertussis infection. CMI to the B. pertussis antigens (especially to the pertussis toxin [PT]) was more frequent and/or intense in DTaP than in DT recipients. No lymphoproliferation differences were found between those with and without a history of pertussis although the DT recipients produced very little interferon-gamma after antigen (particularly PT and filamentous hemagglutinin [FHA]) stimulation. In contrast, seropositivity to PT, but not to pertactin or FHA, was more frequent in DT recipients with history of pertussis than in all other subjects. Thus, years after disease or vaccination, CMI response to PT or circulating PT antibodies appears to be the main distinctive feature of pertussis-protected DTaP recipients or pertussis-affected DT recipients.

An outbreak of febrile gastroenteritis associated with corn contaminated by Listeria monocytogenes

BACKGROUND

On May 21, 1997, numerous cases of febrile gastrointestinal illness were reported among the students and staff of two primary schools in northern Italy, all of whom had eaten at cafeterias served by the same caterer.

METHODS

We interviewed people who ate at the cafeterias about symptoms and foods consumed on May 20. There were no samples of foods left at the cafeterias, but we tested routine samples taken on May 20 by the caterer and environmental specimens at the catering plant. The hospitalized patients were tested for common enteropathogens and toxins.

RESULTS

Of the 2189 persons interviewed (82 percent of those exposed), 1566 (72 percent) reported symptoms; of these, 292 (19 percent) were hospitalized. Among samples obtained from hospitalized patients, all but two of the stool specimens and all blood specimens were negative for common enteropathogens. Listeria monocytogenes was isolated from one blood specimen and from 123 of the 141 stool specimens. Consumption of a cold salad of corn and tuna was associated with the development of symptoms (relative risk, 6.19; 95 percent confidence interval, 4.81 to 7.98; P<0.001). L. monocytogenes was isolated from the caterer's sample of the salad and from environmental specimens collected from the catering plant. All listeria isolates were serotype 4b and were found to be identical on DNA analysis. Experimental contamination of sterile samples of the implicated foods showed that L. monocytogenes grew on corn when kept for at least 10 hours at 25 degrees C.

CONCLUSIONS

Food-borne infection with L. monocytogenes can cause febrile illness with gastroenteritis in immunocompetent persons.

Pattern of susceptibility to measles in Italy. Serological Study Group

On the basis of seroprevalence and incidence data we describe the distribution of individuals susceptible and immune to measles in Italy in 1996-97. In regions where vaccination coverage was at least 70%, approximately 10% of 3-year-old children were susceptible to measles, whereas 40% were in this category in regions with lower vaccination coverage. Seroprevalence among children older than 4 years was similar for the two groups of regions; in the age group 20-39 years it was approximately 95%. During 1990-96 in the regions with lower vaccination coverage the incidence was highest among children aged 4-6 years, and the median age of cases was 7 years; in the regions with higher vaccination coverage, however, the incidence remained at around 5% for the age group 4-16 years, and the overall median age was 10 years. These data confirm the partial reduction in measles incidence in Italy, although transmission has still not been interrupted. The size and geographical distribution of the current pool of susceptible individuals can be expected to present an obstacle to measles elimination if appropriate vaccination strategies, such as catch-up campaigns, are not adopted.

Pertussis eradication: a challenge for public health

Pertussis and pertussis vaccination, particularly the almost simultaneous conduct of different clinical trials in various parts of Europe, has generated much debate in the past ten years. Nonetheless many important public health aspects still need to be c

Incorporation of noncoded amino acids into the N-terminal domain 1-47 of hirudin yields a highly potent and selective thrombin inhibitor

Hirudin is an anticoagulant polypeptide isolated from a medicinal leech that inhibits thrombin with extraordinary potency (Kd = 0.2-1.0 pM) and selectivity. Hirudin is composed of a compact N-terminal region (residues 1-47, cross-linked by three disulfide bridges) that binds to the active site of thrombin, and a flexible C-terminal tail (residues 48-64) that interacts with the exosite I of the enzyme. To minimize the sequence of hirudin able to bind thrombin and also to improve its therapeutic profile, several N-terminal fragments have been prepared as potential anticoagulants. However, the practical use of these fragments has been impaired by their relatively poor affinity for the enzyme, as given by the increased value of the dissociation constant (Kd) of the corresponding thrombin complexes (Kd = 30-400 nM). The aim of the present study is to obtain a derivative of the N-terminal domain 1-47 of hirudin displaying enhanced inhibitory potency for thrombin compared to the natural product. In this view, we have synthesized an analogue of fragment 1-47 of hirudin HM2 in which Val1 has been replaced by tert-butylglycine, Ser2 by Arg, and Tyr3 by beta-naphthylalanine, to give the BugArgNal analogue. The results of chemical and conformational characterization indicate that the synthetic peptide is able to fold efficiently with the correct disulfide topology (Cys6-Cys14, Cys16-Cys28, Cys22-Cys37), while retaining the conformational properties of the natural fragment. Thrombin inhibition data indicate that the effects of amino acid replacements are perfectly additive if compared to the singly substituted analogues (De Filippis V, Quarzago D, Vindigni A, Di Cera E, Fontana A, 1998, Biochemistry 37:13507-13515), yielding a molecule that inhibits the fast or slow form of thrombin by 2,670- and 6,818-fold more effectively than the natural fragment, and that binds exclusively at the active site of the enzyme with an affinity (Kd,fast = 15.4 pM, Kd,slow = 220 pM) comparable to that of full-length hirudin (Kd,fast = 0.2 pM, Kd,slow = 5.5 pM). Moreover, BugArgNal displays absolute selectivity for thrombin over the other physiologically important serine proteases trypsin, plasmin, factor Xa, and tissue plasminogen activator, up to the highest concentration of inhibitor tested (10 microM).

Cell-mediated immune responses in four-year-old children after primary immunization with acellular pertussis vaccines

Cell-mediated immune (CMI) responses to Bordetella pertussis antigens (pertussis toxin [PT], pertactin [PRN], and filamentous hemagglutinin [FHA]) were assessed in 48-month-old recipients of acellular pertussis [aP] vaccines (either from Chiron-Biocine [aP-CB] or from SmithKline Beecham [aP-SB]) and compared to CMI responses to the same antigens at 7 months of age, i.e., 1 month after completion of the primary immunization cycle. None of the children enrolled in this study received any booster of pertussis vaccines or was affected by pertussis during the whole follow-up period. Overall, around 75% of 4-year-old children showed a CMI-positive response to at least one B. pertussis antigen, independently of the type of aP vaccine received, and the proportion of CMI responders were at least equal at 48 and 7 months of age. However, longitudinal examination of individual responses showed that from 20 (against PT) to 37% (against FHA) of CMI responders after primary immunization became negative at 48 months of age. This loss was more than compensated for by conversion to positive CMI responses, ranging from 36% against FHA to 69% against PRN, in other children who were CMI negative at 7 months of age. In 60 to 80% of these CMI converters, a lack of decline or even marked elevation of antibody (Ab) titers against B. pertussis antigens also occurred between 20 and 48 months of age. In particular, the frequency of seropositivity to PRN and FHA (but not to PT) was roughly three times higher in CMI converters than in nonconverters. The acquisition of CMI response to B. pertussis antigens in 48-month-old children was not associated with a greater frequency of coughing episodes lasting >/=7 days and was characterized by a prevalent type 1 cytokine profile, with high gamma interferon and low or no production of interleukin-5, reminiscent of cytokine patterns following immunization with whole-cell pertussis vaccine or natural infection. Our data imply that vaccination-induced systemic CMI may wane by 4 years of age but may be acquired or naturally boosted by symptomless or minor clinical infection by B. pertussis. This might explain, at least in part, the persistence of protection against typical pertussis in aP vaccine recipients despite a substantial waning of both Ab and CMI responses induced by the primary immunization.

Reactogenicity in the elderly of nine commercial influenza vaccines: results from the Italian SVEVA study. Study for the evaluation of adverse events of influenza vaccination

A 10-fold increase of reported adverse events following influenza vaccination in the 1995-1996 campaign was reported. To evaluate the relative reactogenicity of different influenza vaccines a prospective observational study was conducted in 72 Italian local health units (LHU) in the period October-December 1996. Of the 16,637 enrolled individuals aged 65 or more, 27.4% reported the occurrence of at least one adverse event within 72 h of vaccination. The odds ratios, adjusted through a multivariate logistic model, were highest for whole vaccine recipients. Most of the observed events were of moderate clinical severity and were mainly represented by local symptoms. None of the products was found to show an unusual or concerning reactogenicity profile, and no severe events associated with immunization were reported.

Reactogenicity of a three-dose pertussis acellular vaccine catch-up in children 21-40 months of age

The reactogenicity of a three-dose catch-up acellular pertussis (aP) immunization of children at 21-40 months of age was evaluated. Vaccination was well-tolerated: fever > or = 38 degrees C was reported after 5% of administered doses and local reactions after 14-15%. The onset of adverse events was not associated with age at vaccination, interval between doses or previous presence of antibodies against pertussis, whereas injection in sites other than the buttock and presence of the same symptom after a previous dose were associated with higher reactogenicity. Because of the good safety profile of primary aP immunization in children > 1 year of age, catch-up vaccination campaigns could be considered in areas where pertussis whole-cell vaccination uptake has been low and where the number of susceptible children should be reduced to control pertussis circulation.

Infant immunization coverage in Italy: estimates by simultaneous EPI cluster surveys of regions. ICONA Study Group

In 1998, a series of regional cluster surveys (the ICONA Study) was conducted simultaneously in 19 out of the 20 regions in Italy to estimate the mandatory immunization coverage of children aged 12-24 months with oral poliovirus (OPV), diphtheria-tetanus (DT) and viral hepatitis B (HBV) vaccines, as well as optional immunization coverage with pertussis, measles and Haemophilus influenzae b (Hib) vaccines. The study children were born in 1996 and selected from birth registries using the Expanded Programme of Immunization (EPI) cluster sampling technique. Interviews with parents were conducted to determine each child's immunization status and the reasons for any missed or delayed vaccinations. The study population comprised 4310 children aged 12-24 months. Coverage for both mandatory and optional vaccinations differed by region. The overall coverage for mandatory vaccines (OPV, DT and HBV) exceeded 94%, but only 79% had been vaccinated in accord with the recommended schedule (i.e. during the first year of life). Immunization coverage for pertussis increased from 40% (1993 survey) to 88%, but measles coverage (56%) remained inadequate for controlling the disease; Hib coverage was 20%. These results confirm that in Italy the coverage of only mandatory immunizations is satisfactory. Pertussis immunization coverage has improved dramatically since the introduction of acellular vaccines. A greater effort to educate parents and physicians is still needed to improve the coverage of optional vaccinations in all regions.

Rare diseases deserve attention

In August, Eurosurveillance published reports of two outbreaks of trichinellosis detected in 1998 in France and Italy and linked with horse meat imported from Yugoslavia. This issue, otherwise dedicated to botulism, includes a report of a third one. Repor

Persistence of protection through 33 months of age provided by immunization in infancy with two three-component acellular pertussis vaccines. Stage II Working Group

A large, randomized, placebo-controlled clinical trial in Italy on two three-component pertussis vaccines, given as DTaP in infancy, one manufactured by SmithKline and Beecham (SB) and one by Chiron Biocine (CB), found each vaccine to be 84% efficacious through the average age of 24 months. The cohort of children enrolled in the trial was followed with unmodified case ascertainment procedures for nine additional calendar months, during which partial unblinding occurred, for the unvaccinated randomized group. For the DTaP groups, the specific vaccine assignment remained double-blinded throughout the entire additional observation period. Pertussis was defined as paroxysmal cough lasting at least 21 days and confirmed by culture or serology. In the additional 9 months the observed absolute efficacy was 78% (95% CI, 62-87%) for SB DTaP vaccine and 89% (95% CI, 79-94%) for CB DTaP. The relative risk of developing pertussis in SB DTaP recipients compared to CB DTaP vaccinees was 1.99 (95% CI, 1.13-3.51). By combining observations from the initial and additional follow-up periods, the overall observed vaccine efficacy through an average age of 33 months of SB DTaP was 80% and of CB DTaP, 85%.

Antibody responses and persistence in the two years after immunization with two acellular vaccines and one whole-cell vaccine against pertussis

OBJECTIVE

To evaluate the persistence of specific antibodies induced by primary immunization with three doses of two three-component acellular vaccines against pertussis with an observed efficacy of 84%, and one whole-cell vaccine with an observed efficacy of 36%.

STUDY DESIGN

Serum samples were collected from a subsample of 1572 children from the Italian double-blind, placebo-controlled, randomized trial of vaccines used in 15,601 children at three time points: before administration of the first dose of vaccine, and 1 month and approximately 15 months after administration of the third dose. Further evaluation included pooled cross-sectional analysis of serum specimens associated with episodes of cough (which were not laboratory confirmed as pertussis infection) occurring among the entire population enrolled in the trial.

RESULTS

With both acellular vaccines there was a fast and steep decrease in geometric mean antibody titers to pertussis toxin, filamentous hemagglutinin, and pertactin after vaccination. Mean titers were close to the limit of detection 15 months after primary immunization. The immunogenicity of the whole-cell study vaccine was poor 1 month after the third dose, and no antibody was detected in nearly all children 15 months after whole-cell vaccination.

CONCLUSIONS

Although the study acellular pertussis vaccines induced a strong primary specific antibody response in almost all recipients, the duration of the response was limited. Sustained high-level production of antibody to the antigens tested does not account for the observed efficacy of acellular pertussis vaccines.

European Union inventory of resources and means of control of communicable diseases

The Istituto Superiore di Sanita (ISS) in Rome, in collaboration with the Public Health Laboratory Service (PHLS) in London, and the Swedish Institute for Infectious Diseases Control (SIIDC) in Stockholm, is conducting a scientific and technical analysis

Immunogenicity of hepatitis B vaccines among infant recipients of acellular and whole cell pertussis DTP vaccines

The study was conducted to assess the immunogenicity of three doses of two recombinant hepatitis B virus (HBV) vaccines, administered simultaneously with a DT vaccine or one of three different pertussis vaccines combined with diphtheria and tetanus toxoids. The study population consisted of 1237 children selected from the cohort of 15,601 children enrolled in the Italian trial on pertussis vaccines. HBV vaccination was performed at 2, 4 and 12 months of age, with the first two doses concurrent with OPV and DTP vaccination. The DTP vaccines administered in the pertussis trial included one whole cell DTP, licensed in the USA, and two three-component acellular DTaPs, manufactured in Europe. Immunogenicity to HBV was evaluated on serum samples collected 9 months after the third dose of HBV vaccine. Antibodies against HBsAg were detected by ELISA and expressed in mlU/ml. In 13 children, the antibody response was below the protective level of 10 mlU/ml-1. No statistical difference was found among the various study groups with respect to the proportion of children showing protective response. Higher humoral response was observed in children receiving mixed HBV vaccines in each pertussis study groups.

Prevalence of markers of exposure to Bordetella pertussis among Italian young adults

Titers of serum antibody and cell-mediated immunity (CMI) to Bordetella pertussis antigens were assessed in a cohort of Italian military school students for whom the coverage of pertussis vaccination was low. The overall prevalence of IgG antibody above the minimum level of detection (MLD) was 71.6% for pertussis toxin (PT), 81% for pertactin (PRN), and 99% for filamentous hemagglutinin (FHA). Levels of IgA antibody to PT above the MLD were detected in 15.9% of the study participants. CMI to FHA, PRN, and PT was positive in 97%, 100%, and 82% of tested individuals, respectively. Only 9.7% of the participants had neither antibody nor CMI specific to B. pertussis antigens. In the 5-month clinical, microbiological, and serological follow-up conducted during a high-risk period of pertussis, no cases of pertussis were detected. These data, in particular CMI, demonstrate that most Italian young adults are specifically primed against B. pertussis, which should be taken into consideration when future policy on pertussis vaccination is being made in Italy.

Predictors of adverse events after the administration of acellular and whole-cell diphtheria-tetanus-pertussis vaccines

Recurrence of adverse events, the effect of site of injection, and concurrent administration of oral polio vaccine (OPV) and hepatitis B vaccine (HBV) on reactogenicity were assessed in recipients of two acellular pertussis vaccines given in combination with diphtheria and tetanus toxoids (DTaP), one whole-cell DTP vaccine (DTPwc) and one DT vaccine during a double blind, randomized, controlled clinical trial. Local and systemic side reactions were more likely to recur after the administration of DTaP and DT compared with DTPwc. In all vaccine groups, injection in the buttock was associated with a lower rate of common adverse events compared with injection in the thigh, while simultaneous administration of OPV and/or HBV did not increase the risk of onset of side reactions.

A persisting outbreak of hepatitis A in Puglia, Italy, 1996: epidemiological follow-up

In early 1996, an increase in the notifications of hepatitis A cases was identified in the region of Puglia, in the south east of Italy. An outbreak investigation conducted in May 1996 showed a strong association between illness and consumption of raw sea

Pattern of bacterial meningitis in Italy, 1994

During 1994, 603 cases of bacterial meningitis were reported in Italy. Seventy-five percent of cases with determined etiology was due to three agents: Neisseria meningitidis (33.4%), Streptococcus pneumoniae (23.4%) and Haemophilus influenzae (18.6%). The majority of cases due to N. meningitidis and H. influenzae occurred in subjects below five years of age (35.7% and 84.8%, respectively) while S. pneumoniae accounted for 52.8% of meningitis cases in subjects older than 44 year of age. The estimated incidence of N. meningitidis on the national population in 1994 was 0.27 per 100,000. Serogroup B accounted for 62.5% of the serotyped isolates, group C for 23.1%, group A for 7.2%, group W135 for 3.6%, group Y for 1.8%. All tested meningococcal strains were susceptible to penicillin as well as to rifampin. Incidence of meningococcal meningitis in 1994 has been low suggesting that its relative importance compared to other bacteria causing meningitis is likely to change in the future. Therefore, extended surveillance on bacterial meningitis by other etiological agents has to be maintained and implemented in order to undertake the appropriate control measures and evaluate their effect.

Cell-mediated and antibody responses to Bordetella pertussis antigens in children vaccinated with acellular or whole-cell pertussis vaccines. The Progetto Pertosse-CMI Working Group

OBJECTIVE

To examine induction and persistence of cell-mediated immunity (CMI) and antibody responses to Bordetella pertussis antigens in infants receiving antipertussis vaccines.

DESIGN AND SETTING

A randomized, blinded study of 142 children receiving acellular pertussis vaccines combined with diphtheria-tetanus toxoids (DTaP) (DTaP manufactured by SmithKline Beecham [DTaP-SB], Rixensart, Belgium, and DTaP manufactured by Chiron Biocin [DTaP-CB], Siena, Italy), or a whole-cell pertussis vaccine (DTwP) (Connaught Laboratories Inc, Swiftwater, Pa), or a diphtheria-tetanus (DT) (Chiron Biocine) only vaccine. Three doses of each vaccine were given at 2, 4, and 6 months of age, and CMI and antibody responses were evaluated before and at 1 and 14 months after vaccination.

METHODS AND MAIN OUTCOME MEASURES

Cell-mediated immunity was assessed by proliferation of peripheral blood mononuclear cells stimulated in vitro by B pertussis antigens (pertussis toxin, filamentous hemagglutinin, and pertactin). Antibody titers against pertussis toxin, filamentous hemagglutinin, and pertactin were determined by a standardized enzyme-linked immunosorbent assay.

RESULTS

A CMI-positive response to at least 1 B pertussis antigen at 1 or both postvaccination assays was detected in 46%, 55%, and 83% of DTwP, DTaP-SB, and DTaP-CB vaccine recipients, respectively. Frequency of CMI response to individual antigens ranged from less than 4.9% against pertussis toxin in DTwP recipients to 52% against pertactin in DTaP-CB recipients. The postvaccination responses measured at 14 months equalled, or had increased frequency or intensity, that of the 1-month postvaccination responses. Elevated antibody titers against the 3 antigens were present in all DTaP recipients 1 month after vaccination and were higher in CMI-positive children than in CMI-negative children. They fell, however, to low, if not negligible, levels 14 months after vaccination.

CONCLUSIONS

Acellular pertussis vaccines were better inducers of CMI response than the whole-cell vaccine, particularly against pertussis toxin. Once acquired, CMI persisted, in contrast with the rapid antibody decline. Thus, CMI responses could be a useful adjunct to serology in the evaluation of pertussis vaccine immunogenicity and a better correlate of long-term immunity to B pertussis than antibody titers.

Incidence of invasive Haemophilus influenzae type b disease in Italian children

To estimate the incidence of Haemophilus influenzae type b (Hib) invasive disease in Italian infants we performed a prospective study in a cohort of newborns enrolled for a randomized trial on safety and efficacy of three pertussis vaccines and followed for onset of serious disease or pertussis. The overall cumulative incidence observed in 15,601 children was 51.3/100,000 for all invasive Hib infections and 38.4/100,000 for Hib meningitis, over 27 months of observation. The incidence density of all invasive Hib disease was 28.7/100,000 person-years, while meningitis occurred with an incidence of 21.5/100,000 person-years. Among the eight cases detected, six were meningitis, one sepsis, and one cellulitis. The child with sepsis died. The incidence and epidemiology of invasive Hib disease in Italy are comparable to those reported from other European countries. Cost-benefit analyses are needed for planning Italian vaccination policy.

Case definitions

The definition of a case of pertussis is an essential point in evaluating and comparing the results from the seven studies on pertussis vaccines presented at the Symposium. An assessment of the impact of case definition on the evaluation of vaccine efficacy has been performed on the Italian data-set, by comparing the clinical presentation of cough illnesses which were laboratory-confirmed as B. pertussis infection with those not-confirmed, by study vaccine. The results show that the estimate of vaccine efficacy is greatly variable by the choice of case definition and dependent on the study design. The assessment of the effect of each vaccine should be performed by using various clinical endpoints and the method used in detection of suspected cases in each study should be carefully evaluated to verify comparability of results.

A foodborne outbreak of gastroenteritis involving Listeria monocytogenes

An outbreak of gastroenteritis occurred in Italy among 39 persons who had attended a private supper. All guests were previously healthy, young, non-pregnant adults; 18 (46%) had symptoms, mostly gastrointestinal (78%), with a short incubation period. Four were hospitalized with acute febrile gastroenteritis, two of whom had blood cultures positive for Listeria monocytogenes. No other microorganisms were recovered from the hospitalized patients' specimens. Epidemiological investigation identified rice salad as the most likely vehicle of the food-borne outbreak. L. monocytogenes was isolated from three leftover foods, the kitchen freezer and blender. Isolates from the patients, the foods and the freezer were indistinguishable: serotype 1/2b, same phage type and multilocus enzyme electrophoretic type. Eight (36%) of 22 guests tested were found to have antibodies against L. monocytogenes, compared with none of 11 controls from the general population. This point source outbreak was probably caused by infection with L. monocytogenes. Unusual features included the high attack rate among immunocompetent adults and the predominance of gastrointestinal symptoms.

Predicting the accrual rate in a vaccine clinical trial: an a posteriori evaluation of the feasibility study

To estimate the expected accrual rate in a double blinded controlled randomized trial of the absolute clinical efficacy of three anti-pertussis vaccines in infants, we performed a series of surveys among mothers and physicians in the areas to be considered for participation in the trial. In this paper, we compared the predicted enrollment with the actual enrollment achieved at the end of the recruitment phase of the trial. The predicted enrollment rate was 27%, while the observed rate was 26%. Results from the feasibility study were highly predictive of actual enrollment rate. In the local health units (USL) where such assessments were carried out, the accrual rate, was higher than those not participating in the feasibility phase.

An outbreak of hepatitis A in Puglia, Italy, 1996

In the region of Puglia, in the south east of Italy (population: 4 million), the number of notifications of hepatitis A virus (HAV) infection increases in a two yearly cycle. In 1992 a very large outbreak was observed, but no epidemiological investigation

A controlled trial of two acellular vaccines and one whole-cell vaccine against pertussis. Progetto Pertosse Working Group

BACKGROUND

Concern about both safety and efficacy has made the use of whole-cell pertussis vaccines controversial. In some European countries, including Italy, the rate of vaccination against pertussis is low.

METHODS

We conducted a double-blind trial in Italy in which infants were randomly assigned to vaccination at two, four, and six months of age with an acellular pertussis vaccine together with diphtheria and tetanus toxoids (DTP); a DTP vaccine containing whole-cell pertussis (manufactured by Connaught Laboratories); or diphtheria and tetanus toxoids without pertussis (DT). The acellular DTP vaccine was either one containing filamentous hemagglutinin, pertactin, and pertussis toxin inactivated with formalin and glutaraldehyde (SmithKline Beecham) or one with filamentous hemagglutinin, pertactin, and genetically detoxified pertussis toxin (Chiron Biocine). Pertussis was defined as 21 days or more of paroxysmal cough, with infection confirmed by culture or serologic testing.

RESULTS

The efficacy of each vaccine, given in three doses, against pertussis was determined for 14,751 children over an average of 17 months, with cases included in the analysis if cough began 30 days or more after the completion of immunization. For both of the acellular DTP vaccines, the efficacy was 84 percent (95 percent confidence intervals, 76 to 89 percent for Biocine DTP and 76 to 90 percent for SmithKline DTP), whereas the efficacy of the whole-cell DTP vaccine was only 36 percent (95 percent confidence interval, 14 to 52 percent). The antibody responses were greater to the acellular vaccines than to the whole-cell vaccine. Local and systemic adverse events were significantly more frequent after the administration of the whole-cell vaccine. For the acellular vaccines, the frequency of adverse events was similar to that in the control (DT) group.

CONCLUSIONS

The two acellular DTP vaccines we studied were safe, immunogenic, and efficacious against pertussis, whereas the efficacy of the whole-cell DTP vaccine was unexpectedly low.

[To what extent is breast feeding practiced in Italy today?]

OBJECTIVES

During a survey regarding infant health in 7 regions, diffusion and length of time of breast-feeding nowadays in Italy were studied.

MATERIALS AND METHODS

By OMS Epi methodology, 210 children sampled from each area of study and specialized health workers carried out the interviews at home using a specific questionnaire. The mothers were questioned about the length of time they breast fed their child.

RESULTS

76% of mothers said they breastfed, 32% said they did it for less than 3 months and 44% for more. In each area, the percentage of breastfeeding was 70% or more. This percentage changed only if the birth weight was very low or the mothers' instruction was high, but this is probably because the most cultured mothers answered easier they breast fed longer.

DISCUSSION

It seems that mothers are pro-breastfeeding and, in each region, just a quarter of them don't practise it. Besides, about half women breastfed for more than 3 months. This study doesn't permit us to know why some women don't breastfeed or why they wean their children too early. For this reason, we need to curry out further studies.

[Epidemiology of invasive infections with Haemophilus influenzae type b in the world and in Italy]

The incidence of Haemophilus influenzae type b (Hib) disease in the 0-5 years age group has been studied in many countries. In the United States, before the introduction of mass vaccination, the incidence of invasive Hib disease ranged from 7 per 100,000 in the 4-5 years age group to 452 pert 100,000 in the 6-11 months age group. In Europe, the incidence of this disease has been estimated to range from 21 to 60 per 100,000 per year in the 0-5 years age group. Hib infection is mainly transmitted by the respiratory route. Risk factors of the disease include: attending a day-care center, a high number of household members, low socio-economic level, age less than two years, and belonging to certain ethnic groups. Accurate estimates of the incidence of invasive Hib disease do not exist in Italy. Among the 15,601 children participating in the "Progetto Pertosse", a clinical trial for the evaluation of antipertussis vaccines, there occurred six cases of Hib meningitis, one of Hib sepsis, and one of Hib cellulitis. These episodes yield an incidence density of 28.7 per 100,000 person-years in the 2-30 month age group. Incidence data will also need to be collected for children in the 30 months-5 years age group before attempting a cost-benefit analysis with the aim of planning a mass vaccination.

[Vaccinal coverage for measles and pertussis: a study in 7 regions of Italy]

During the year 1993 a series of surveys aimed to estimate the immunization coverage against measles and pertussis have been carried out in seven Italian regions and two large towns (Milan and Naples). Mothers of children aged between 12 and 23 months, randomly selected from the list of newborns, by using the EPI cluster sampling, have been interviewed in order to determine the reasons for absent or incomplete vaccinations. The observed coverage for pertussis ranges between 8% in the Molise region and 71% in the town of Milan; coverage for measles ranges between 9% in the town of Naples and 52% in the region Lombardy. The most commonly reported reason for not-vaccinating for pertussis has been the negative advise given by the caring physician. Immunization against measles has often not been administered because of relative contraindications and the negative advise by the physicians. The coverage for the two non-compulsory vaccinations are low compared to compulsory vaccinations and to the immunization level reported for most European countries, pointing out that further health education is needed for improving the up-take of such voluntary vaccinations.

HIV Prevalence and Frequency of Risk Behavior in Injecting Drug Users Entering Treatment and Out of Treatment: A Cross-Sectional Study in Five Italian Cities

We conducted a study to describe current patterns of drug-related behaviors, and to identify characteristics that may distinguish injecting drug users entering treatment from those out of treatment, in five Italian cities. Overall, 1,180 subjects were recruited — 568 entering treatment and 612 out of treatment. Male to female ratio was 6.6:1. The median age was similar in the two groups. A high proportion of injecting drug users recruited out of treatment had been in treatment at least once. HIV prevalence among injecting drug users entering treatment was not higher than that of those who were out of treatment. Furthermore, a large proportion of injecting drug users who still were out of treatment reported having adopted safe behaviors. The results of the study emphasize the need to implement outreach programs aimed at harm reduction.

Tuberculosis and AIDS: a retrospective, longitudinal, multicentre study of Italian AIDS patients. Italian group for the study of tuberculosis and AIDS (GISTA)

We report the results of a retrospective, longitudinal, multicentre study which estimated the cumulative incidence of tuberculosis in patients who eventually develop AIDS, investigated the characteristics of AIDS patients in relation to the development of tuberculosis, and endeavoured to determine the degree of HIV-induced immunosuppression at which tuberculosis occurs. The Infectious Disease Units of 23 hospitals located in 11 of the 20 regions of Italy participated in this study. We investigated 1691 patients with AIDS diagnosed in 1988 and 1989 and reported to the National AIDS Registry by participating units before the end of December 1990. By that time M. tuberculosis had been cultured from 193 patients (11.4%). Compared with intravenous drug users (the largest HIV transmission category), only homosexual men had a statistically significant lower risk of tuberculosis (relative risk = 0.65; 95% confidence interval 0.43-0.99). The median count of CD4+ lymphocytes at the time tuberculosis was diagnosed was 82/mm3 (range 1-752); only four patients (2.1%) had CD4+ lymphocyte counts of more than 500/mm3, and 36 (18.7%) of over 200/mm3. We conclude that in Italy the proportion of AIDS patients who develop tuberculosis is higher than in other industrialised countries and differences in the incidence of tuberculosis among various HIV-transmission categories are less marked than in other western countries. Tuberculosis associated with HIV infection may occur in those with widely differing CD4+ counts, although the risk increases consistently in proportion to the degree of immunosuppression.

Simultaneous infection with three different S. enteritidis strains in a nursing home resident

A culture taken from a nursing home resident as part of a S. enteritidis outbreak was found to have a mixed infection due to three different strains of S. enteritidis. One of the three strains belonged to phage type (PT) 4, one to PT6 and one reacted with phages but did not conform to any typing scheme (RDNC). All three strains had the 38.9 megadaltons (MDa) plasmid found in the isolates from the outbreak-related cases, in addition the PT6 and RDNC strains harboured a 69.9 MDa plasmid. The importance of phage typing and plasmid analysis for S. enteritidis strain characterization and their epidemiologic and bacterial significance are discussed.

Tuberculosis in HIV-infected subjects in Italy: a multicentre study. The Gruppo Italiano di Studio Tubercolosi e AIDS

OBJECTIVES

To evaluate the strength of the association between tuberculosis and HIV infection in Italy, to assess the pattern of this association in relation to HIV transmission categories, and to describe clinical presentation of tuberculosis in a large group of Italian HIV-infected subjects.

DESIGN

Multicentre review of clinical records.

SETTING

Twenty-one infectious disease hospital units in nine of the 20 administrative regions of Italy.

PATIENTS, PARTICIPANTS

All HIV-infected adults observed by each participating unit (in- and outpatients) between 1985 and 1989.

MAIN OUTCOME MEASURE

Culture-proven tuberculosis.

RESULTS

A total of 306 cases of tuberculosis were observed. Of these, 85 were pulmonary, 167 extrapulmonary, and 54 both pulmonary and extrapulmonary. The proportion of HIV-infected subjects diagnosed with tuberculosis increased during the study period from three out of 1380 (0.2%) in 1985 to 152 out of 6504 subjects (2.3%) in 1989 (P less than 0.0001). Two hundred and twenty-six of the 2760 (8.19%) patients with AIDS had tuberculosis within 12 months of AIDS diagnosis; the proportion of AIDS patients with tuberculosis remained stable after 1985. Compared with AIDS patients who were intravenous drug users, only homosexual AIDS patients had a significantly lower proportion of tuberculosis (178 out of 1958 versus 30 out of 522; P less than 0.02).

CONCLUSIONS

Our data show that tuberculosis is quite common among HIV-infected subjects in Italy, and suggest that the risk of tuberculosis in these subjects has not changed. There are some differences between the pattern of the association between tuberculosis and HIV infection in Italy, compared with other industrialized countries.

Epidemiology of pertussis in a developed country with low vaccination coverage: the Italian experience

In Italy pertussis vaccination is optional. Fewer than 40% of children younger than 5 years of age are vaccinated, and pertussis remains a common childhood disease. We use data from a variety of sources to examine trends and characteristics of Italian children with pertussis and reasons behind the low vaccine coverage. Approximately 25% of Italian children have experienced clinical pertussis by their fifth birthday. The disease is most severe in those less than 1 year of age; in this group an estimated 1 in 14 cases are hospitalized and 1 in 850 die. The incidence appears to be increasing in the 1- to 4-year age group despite increased vaccination coverage. The low vaccine coverage appears to be caused by the ambivalence of the Italian pediatric community about the vaccine rather than parental concerns about vaccine safety. Legislation is being considered to make pertussis vaccination mandatory.

Sexual lifestyles in injecting drug users in Italy: potential for HIV infection transmission. First Multicentre Study Group

To better target efforts aimed at modifying sexual behaviour among injecting drug users (IDUs), we conducted a detailed analysis of sexual partners and practices reported by 1214 Italian heterosexual drug users during the period June 1985-June 1987. Females were more likely to have only drug-using partners (42.8% vs 17.1%), while males were more likely to have only non drug-using partners (50.5% vs 21.4%). Female drug users were more likely to report either one partner or greater than 10 partners, while males were more likely to report 2-10 partners. Nearly 90% of women with only drug-using partners had only one partner. Overall, 29% of women with only non drug-using partners reported that they always used condoms. This proportion increased to 65% among women with greater than 10 non drug-using partners. In Italy, male IDUs may play a greater role than female IDUs in sexual transmission of HIV infection to the heterosexual non drug-using partners.

AIDS cases in adolescents and young adults in Italy: inferences from descriptive epidemiology

To assess the magnitude of the AIDS epidemic in the Italian adolescent (13-19 years) and young adult (20-24 years) age groups, data on AIDS cases notified to the AIDS Operational Centre as of 31 March 1990 were used. Of the 6068 reported AIDS cases, 0.7% occurred among adolescents and 15.7% among young adults. Among adolescents most cases were haemophiliacs (45.4%), while among young adults, drug use was the most frequently reported mode of transmission (87.5%). Females were more likely than males to contract the disease through the heterosexual contact in both the adolescent (20.0% vs 0%) and in young adult (15.1% vs 0.7%) age groups. Among young adults a geographical trend was present with a decrease in case rates from north to south, while for adolescents the rates were higher in northern and southern than in central Italy. If the incidence of AIDS is to be reduced in Italy, further efforts should be made to target the adolescent age group, since many of the young adult cases are likely to have resulted from HIV infection during adolescence.

Epidemiological use of drug prescriptions as markers of disease frequency: an Italian experience

All Italian citizens are covered by the National Health Service (NHS) and medical records of individual drug prescriptions are routinely collected and processed. A procedure entitled EPIFAR has been developed which, on the basis of a computer routine, makes it possible to trace back the prescription history of each individual included in the NHS. The validity of information gathered through the EPIFAR procedure to provide estimates of tuberculosis (TB) prevalence has been evaluated. A comparison with routine surveillance data has been made. The EPIFAR procedure identified a total figure of TB patients seven times higher than that from official notifications. A sample survey was conducted among the prescribing physicians in order to quantify the proportion of TB cases among subjects receiving prescriptions of anti-TB drugs. According to general practitioner recall 66.4% of the patients were treated because of TB diagnosis, TB prophylaxis and TB relapse.