Hib-EuroSud'95: the South exists

Impact of non-routine vaccination on the incidence of invasive Haemophilus influenzae type b (Hib) disease: experience in the autonomous region of Valencia, Spain

OBJECTIVE

This study assessed the impact of non-routine vaccination against invasive Haemophilus influenzae (Hib)disease before the introduction of universal childhood Hib vaccination.

METHODS

Data were obtained from a prospective surveillance program for invasive bacterial diseases in children <15 years of age that was begun in the Autonomous Region of Valencia on 1 December 1995.

RESULTS

An incidence of 15.5 cases of invasive Hib disease per 100,000 children <5 years of age was reported in the first year of the surveillance program (from 1 December 1995 to 30 November 1996), when Hib vaccination coverage was estimated to be 32.5%. An increase in vaccination coverage to 44% in the second year (1 December 1996 to 30 November 1997) was associated with a reduction in disease incidence to 3.3 cases per 100,000. After the initiation of universal vaccination in December 1998, only two cases were reported. The effectiveness of non-routine vaccination was 71% in 1997.

CONCLUSIONS

These results show that before the introduction of routine childhood Hib vaccination, widespread use of the vaccine can dramatically reduce the occurrence of invasive Hib disease.

National Surveillance System and Hib meningitis incidence in Italy

In 1994, the Italian Ministry of Health implemented a National Surveillance System to obtain data on the incidence of bacterial meningitis and its causative agents, including Haemophilus influenzae type b (Hib). As a consequence, case reporting of Hib meningitis is increasing year by year; in 1996, there were 126 notifications, of which 73% were in children under 2 years of age. Although underreporting still exists, parallel prospective or retrospective epidemiological surveys conducted in some Italian Regions allowed for partial correction of the incidence of Hib meningitis (up to 18.5/100,000 population in 1994).

Immune responses to administration of a vaccine against Haemophilus influenzae type B in splenectomized and non-splenectomized patients

OBJECTIVES

we investigated the cause of hypo-responsiveness to vaccines in splenectomized subjects.

METHODS

we evaluated the immune responses to a Haemophilus influenzae type b vaccine and the sizes of lymphocyte subpopulations in 25 splenectomized and 45 non-splenectomized thalassaemic patients, in 12 individuals who had been splenectomized after trauma and in 20 controls.

RESULTS

the immune response in the controls was significantly higher (P < 0.001) than in splenectomized patients after trauma and in both, the response was higher (P < 0.001) than in thalassaemic patients. In asplenic subjects after trauma, percentages of CD3 and CD4 cells were lower (P < 0.001) than in patients in the other groups; the controls had higher percentages of CD8 cells (P < 0.001) than patients in the other groups. The natural logarithm of the mean percentage of (CD19 showed a quadratic trend from thalassaemic patients through asplenic subjects to controls (P < 0.001). Levels of CD16+ natural killer (NK) cells were higher (P < 0.001) only in asplenic subjects after trauma.

CONCLUSIONS

the significant decrease in the immune response of the splenectomized thalassaemic patients vs. non-splenectomized thalassaemic patients may, in part, be due to their basic immunological condition. Thus, the best strategy for protecting these subjects is to vaccinate them before the splenectomy.

Assessment of the immunogenicity and reactogenicity of a quadrivalent diphtheria, tetanus, acellular pertussis and hepatitis B (DTPa-HBV) vaccine administered in a single injection with Haemophilus influenzae type b conjugate vaccine, to infants at 2, 4 and 6 months of age

This double-blind, randomised study was performed to assess the immunogenicity and reactogenicity of three lots of a quadrivalent diphtheria-tetanus-acellular pertussis-hepatitis B vaccine (DTPa-HBV) co-administered with three lots of Haemophilus influenzae type b conjugate (Hib) vaccine in one injection, as a primary vaccination course in healthy infants at 2, 4 and 6 months of age. 269 infants (8-11 weeks of age) were randomly allocated to three groups to receive DTPa-HBV/Hib vaccines, concomitantly with oral polio vaccine. Blood samples for antibody determinations were taken before vaccination and 1 month after the third dose in 262 subjects. Local and general symptoms were recorded by parents on diary cards. All vaccinees had post-vaccination protective anti-D and anti-T (> or = 0.1 IU ml-1) antibodies, and 98% had protective anti-HBs antibody titres (> or = 10 mIU ml-1). There were no statistically significant differences between groups in post-vaccination anti-D, anti-T, anti-HBs antibody geometric mean titres (GMT), these being 3.49 IU ml-1, 5.92 IU ml-1 and 1109 mIU ml-1, respectively. All subjects responded to three pertussis components, i.e. pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN). Although statistically significant differences in GMTs of anti-PT, anti-FHA and anti-PRN were found between groups, these were not believed to be of any clinical relevance as the minimum GMTs were 60, 193 and 230 EL.U ml-1 for anti-PT, anti-FHA and anti-PRN, respectively. There were no statistically significant differences in anti-PRP antibody GMT (4.05 micrograms ml-1) between groups, 100% and 85% of subjects having titres > or = 0.15 and 1.0 microgram ml-1, respectively. No symptoms were reported for one third of the subjects. Fever (> 38 degrees C) was reported after 16% of doses, with < 1% having > 39.5 degrees C. Almost all local and general symptoms were mild or moderate, and lasted less than 48 h. No subject dropped out due to a severe adverse reaction. The administration of an experimental mix of DTPa-HBV and Hib vaccines in a single injection is safe, well-tolerated and immunogenic for all vaccine components.

Haemophilus influenzae type b disease and vaccination in Europe: lessons learned

OBJECTIVE

To scrutinize the experiences of those European countries that have played a central role in understanding the behavior of and vaccination for Haemophilus influenzae type b (Hib) diseases, to enlighten weaknesses and to explore whether lessons learned would benefit other countries in combating Hib.

DESIGN

Epidemiologic and clinical data on Hib infections and vaccinations were analyzed, including all disease manifestations and all age groups. To improve reliability, sources that used active case finding were especially searched for.

RESULTS

In the prevaccination era meningitis represented 40 to 70% of all classical Hib diseases. Epiglottitis was the second most common presentation, except in southern Europe (data not available from former socialist countries). The overall incidence of meningitis and of all Hib disease combined for children ages 0 to 4 years was 23 and 41 per 100000, suggesting 9900 and 17800 cases per year, respectively. Including all age groups and entities, >20000 Hib cases occurred annually. Vaccination, accomplished with two or three primary doses and a late booster, has almost eliminated Hib disease in >10 countries, and >10000 cases per year are prevented. An age analysis of Hib meningitis suggests that strong early immunogenicity is not as imperative in Europe as in some other regions. The incidence of non-type b H. influenzae infections has not increased.

CONCLUSIONS

With Hib epidemiology comparable with that in Europe, good protection is achieved by various conjugate vaccines also with two primary doses only. However, active research on the whole Hib issue should be a priority, especially in southern and eastern European countries.