Alessandra Anemona

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

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%.

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.

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 diseases 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.

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.

A DIFFERENCE IN RELATIVE EFFICACY OF TWO DTaP VACCINES IN CONTINUED BLINDED OBSERVATION OF CHILDREN FOLLOWING A CLINICAL TRIAL. • 1021

In 1992-94, a randomized, double blind, placebo-controlled clinical trial of two acellular and one whole-cell pertussis vaccines was conducted in Italy. Each acellular vaccine (one manufactured by SmithKline Beecham [SB] and one by Chiron Biocine [CB]) contained filamentous hemagglutinin, pertactin and inactive pertussis toxin, the latter being detoxified by formalin and glutaraldehyde in SB DTaP and genetically detoxified in CB DTaP. Primary immunization at 2, 4 and 6 months of age provided an efficacy for each DTaP of 84% in preventing confirmed pertussis of 21 or more days of paroxysmal cough, over an average of 17 months of follow-up. The incidence rate ratio (IRR) of pertussis in recipients of SB and CB vaccines was 1.0 with 37 cases in 4,481 children and 36 cases in 4,452, respectively. In 1995, during additional blinded follow-up of the same cohorts through September 30, a total of 53 pertussis cases have been diagnosed in DTaP recipients through an average age of 35 months. Thirty-five cases of confirmed pertussis occurred in SB DTaP recipients in the nine-month period and 18 cases in CB DTaP recipients. Although initially both vaccines exhibited equivalent high efficacy, in a further period of observation the incidence in CB DTaP recipients was significantly lower. Table

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.