L. Salleras

Impact and effectiveness of a mass hepatitis A vaccination programme of preadolescents seven years after introduction

AIMnTo investigate the impact of a mass hepatitis A vaccination programme in preadolescents seven years after introduction in terms of its effectiveness and the prevented fraction.nnnSETTINGnThe age distribution of notified cases and incidence rates in Catalonia (Spain) in the periods before (1992-1998) and after (1999-2005) introduction of the vaccination programme were compared.nnnMAIN RESULTSnThe incidence rates in the whole population were 5.51 per 100,000 person-years in the 1992-1998 period and 2.98 in the 1999-2005 period. The rate reduction in the 10-19 years age group was 72.43% and was more than 45% in the 5-9 years and 20-29 years age groups. The effectiveness of the vaccination programme was 99.04 (95% CI: 93.11-99.88) and the prevented fraction in the 12-19 years age group was 90.13% (95% CI: 84.47-90.89).nnnCONCLUSIONSnThe universal vaccination programme of preadolescents has had an important impact on hepatitis A in Catalonia, not only in vaccinated cohorts but also in non-vaccinated age groups due to a herd immunity effect.

Changes in serotypes causing invasive pneumococcal disease (2005–2007 vs. 1997–1999) in children under 2 years of age in a population with intermediate coverage of the 7-valent pneumococcal conjugated vaccine

Serotypes causing invasive pneumococcal disease (IPD) in children aged <2 years in Catalonia (Spain) before and after licensing of the 7-valent pneumococcal conjugated vaccine (7vPCV) were assessed, using samples taken during 1997-1999 and 2005-2007 respectively. The distribution of serotypes causing IPD within these groups was obtained by serotyping strains sent by 22 Catalan hospitals to the Carlos III Health Institute, Madrid. Between 1997-99 and 2005-2007, the proportion of vaccine serotypes causing IPD in Catalonia fell from 70.54% to 31.67% (p <0.0001). The proportion of vaccine-related serotypes, mainly serotype 19A, increased from 9.82% to 32.50% (p <0.0001). The proportion of non-vaccine, non-related serotypes (serotypes not related to vaccine serotypes) rose from 19.64% to 35.83% (p <0.05). Within this group, the proportions of serotype 24F increased significantly. There has been a change in the distribution of serotypes isolated from cases of IPD in children <2 years old in Catalonia, comprising a reduction in the proportion of 7-valent vaccine serotypes, a rise in vaccine-related serotypes, especially 19A, and a smaller rise in non-vaccine, non-related serotypes, especially serotype 24F. A new 13-valent vaccine will cover 77.91% of the serotypes causing IPD in children <2 years old in Catalonia from 2005 to 2007.

The seroepidemiology of B. pertussis infection in Catalonia, Spain

A survey of the seroprevalence of pertussis antibodies in a representative sample of the population from Catalonia was carried out. Ninety-seven municipalities and 30 schools were randomly selected to recruit the 2126 subjects who participated in the study. A serum sample was obtained from all individuals participating in the study in order to determine levels of pertussis toxin (PT) and filamentous hemagglutinin (FHA) antibodies by ELISA test. Sociodemographic data were collected for all subjects. The prevalence of PT antibodies was 75% and that of FHA antibodies 89%. Significant increments were observed with age, both in the prevalence of PT (P < 0.0001) and of FHA (P = 0.018). Of the sociodemographic variables studied, only urban habitat was significantly associated to PT antibodies. The agreement observed among the two types of antibodies studied was weak (K = 0.264). Routine revaccination with the acellular vaccine in children over 7 years of age, in adolescents and adults seems a reasonable strategy to prevent the appearance of cases of pertussis in the community.

Impact of mass vaccination with polysaccharide conjugate vaccine against serogroup C meningococcal disease in Spain

During the fourth quarter of 1997, a vaccination campaign using the meningococcal C polysaccharide vaccine was carried out in 14 autonomous regions of Spain. The remaining three regions did not participate. In the last quarter of the year 2000, a mass vaccination campaign using the meningococcal C conjugated vaccine was carried out in all regions. In the year 2001 the incidence decreased in all regions, although the decrease was greater in regions that did not vaccinate in 1997. In contrast, case fatality rates did not decrease. During 2001, the incidence rate of meningococcal C disease was still lower (0.32 per 100000 persons-year) in the regions that vaccinated in 1997 with the polysaccharide vaccine than in those that did not (0.64 per 100000 persons-year).

Measles immunity and vaccination policy in Catalonia

The prevalence of antibodies against measles in a representative sample of the school population in Catalonia was established and the results compared with previous studies. The study was carried out in 1996 using blood samples obtained from schoolchildren aged 6-7 years, 10-11 years, 13 14 years and 15-16 years. 1231 schoolchildren were studied. The global prevalence of antibodies was 96.3%, and a considerable increase was observed with respect to the prevalence in 1986 (89.4%). The level of antibodies was 94% at 6-7 years and 10-11 years, 99.7% at 13-14 years and 98.3% at 15 16 years. These data would suggest the advancement of the administration of the second dose of measles-mumps rubella vaccine to 4 6 years instead of at 11 years.

Serotype 3 is a common serotype causing invasive pneumococcal disease in children less than 5 years old, as identified by real-time PCR

Serotype 3 is one of the most often detected pneumococcal serotypes in adults and it is associated with serious disease. In contrast, the isolation of serotype 3 by bacterial culture is unusual in children with invasive pneumococcal disease (IPD). The purpose of this study was to learn the serotype distribution of IPD, including culture-negative episodes, by using molecular methods in normal sterile samples. We studied all children <5xa0years of age with IPD admitted to two paediatric hospitals in Catalonia, Spain, from 2007 to 2009. A sequential real-time polymerase chain reaction (PCR) approach was added to routine methods for the detection and serotyping of pneumococcal infection. Among 257 episodes (219 pneumonia, 27 meningitis, six bacteraemia and five others), 33.5% were identified by culture and the rest, 66.5%, were detected exclusively by real-time PCR. The most common serotypes detected by culture were serotypes 1 (26.7%) and 19A (25.6%), and by real-time PCR, serotypes 1 (19.8%) and 3 (18.1%). Theoretical coverage rates by the PCV7, PCV10 and PCV13 vaccines were 10.5, 52.3 and 87.2%, respectively, for those episodes identified by culture, compared to 5.3, 31.6 and 60.2% for those identified only by real-time PCR. Multiplex real-time PCR has been shown to be useful for surveillance studies of IPD. Serotype 3 is underdiagnosed by culture and is important in paediatric IPD.

Effectiveness of 7-valent pneumococcal conjugate vaccine in the prevention of invasive pneumococcal disease in children aged 7-59 months. A matched case-control study.

The aim of this study was to evaluate the effectiveness of the administration of the 7-valent pneumococcal conjugate vaccine in a region with an intermediate vaccination coverage. A matched case-control study was carried out in children aged 7-59 months with invasive pneumococcal disease (IPD) admitted to two university hospitals in Catalonia. Three controls matched for hospital, age, sex, date of hospitalization and underlying disease were selected for each case. Information on the vaccination status of cases and controls was obtained from the vaccination card, the childs health card, the hospital medical record or the vaccination register of the primary healthcare center where the child was attended for non-severe conditions. A conditional logistic regression analysis was made to control for the effect of possible confounding variables. The adjusted vaccination effectiveness of the complete vaccination schedule (3 doses at 2, 4 and 6 months and a fourth dose at 15 months, 2 doses at least two months apart in children aged 12-23 months or a single dose in children aged >24 months) in preventing IPD caused by vaccine serotypes was 93.7% (95% CI 51.8-99.2). It was not effective in preventing cases caused by non-vaccine serotypes. The results of this study carried out in a population with intermediate vaccination coverage confirm those of other observational studies showing high levels of effectiveness of routine 7-valent pneumococcal conjugate vaccination.

Epidemiology of hepatitis A before and after the introduction of a universal vaccination programme in Catalonia, Spain.

Summary.u2002 A universal vaccination program for preadolescents, aged 12u2003years, with the hepatitis Au2003+u2003B vaccine was introduced in 1998 in Catalonia (Spain) with the aim of protecting the whole population against hepatitis A. The hepatitis Au2003+u2003B vaccine program replaced the hepatitis B vaccination program for preadolescent started in 1991. The impact of the hepatitis Au2003+u2003B vaccination program was studied by assessment of the trend of reported cases of hepatitis A. All cases of viral hepatitis reported from 1992 to 2006 were included in the study. To evaluate changes in the epidemiology of hepatitis A, two periods were considered: a prevaccination period (1992–1998) and a post‐vaccination period (2001–2006). The ratios of the rates were calculated according to age and sex. The comparison of rates and proportions was made by calculation of the normal z statistic. A total of 7536 cases of viral hepatitis were reported, of which 4109 (54.52%) were hepatitis A. The incidence rate of hepatitis A fell from 5.44 per 100u2003000 person‐years in the prevaccination period to 3.02 in the post‐vaccination period. In males, the rate fell from 6.85 to 3.89 and in females from 4.10 to 2.18. The male‐female ratio of incidence rates was lower in the post‐vaccination period. In males the global decline of incidence rate was 43.26% and in females 46.96%. The greatest decline occurred in the 15 to 19u2003years age group in both sexes (79.1% in men and 78.34% in women) but declines in the 10–14u2003years age group were also very important (69.21% and 67.88%, respectively). In conclusion, hepatitis A incidence fell in Catalonia in the post‐vaccination period in vaccinated adolescents and also in other unvaccinated groups who have benefited from the indirect effects of the vaccination program.

Measles antibodies and response to vaccination in children aged less than 14 months: implications for age of vaccination.

Passive immunity against measles decreases during the first months of life. The objective of this study was to determine titres of measles antibodies in children aged 9-14 months and their mothers before vaccination, and the childrens response to vaccination. Blood samples were collected by capillary puncture before and 28 days after vaccination. Samples were obtained between February and June 2007 during an ongoing measles outbreak. Titres of specific measles IgG antibodies were determined by enzyme-linked immunosorbent assay. Seroconversion was defined as the presence of antibodies after vaccination in subjects without antibodies before vaccination. Maternal antibodies were present in 37·7% of all 69 children included and in 45·1% of children aged 9 months. Of the 51 children in whom a second sample was obtained, 31 (60·8%) were seronegative before vaccination and 61·3% seroconverted. Interference of maternal antibodies was 30%. Advancing the first dose of measles vaccination from 15 to 12 months is a correct strategy, given the increase in the time of susceptibility of infants to measles.

Contacts with children and young people and adult risk of suffering herpes zoster

We carried out a matched case-control study to analyze the possible association between exposure to the children and the risk of suffering herpes-zoster in adulthood. Cases of herpes zoster in immunocompetent healthy patients aged ≥ 25 years seen in the dermatology department of the Sagrado Corazón Hospital in 2007-2008 were matched with four controls. Data were analyzed using conditional logistic regression. 153 cases and 604 matched controls were included. Contacts with children were significantly associated with a reduction in the risk of suffering herpes zoster in adulthood (adjusted OR 0.56 [0.37-0.85]). Herpes-zoster vaccination in immunocompetent people aged ≥ 50 years could counteract the possible negative effects of mass varicella vaccination in childhood on the epidemiology of herpes zoster in adults.