The impact of COVID-19 pandemic on the incidence of acute gastroenteritis outbreaks in Catalonia (Spain).

We carried out a retrospective study of acute gastroenteritis (AGE) outbreaks reported between 1 January 2015 and 31 December 2021 in Catalonia (Spain) to compare the incidence from 2015 to 2019 with that observed from 2020 to 2021. We observed a higher incidence rate of outbreaks during the prepandemic period (16.89 outbreaks/1,000,000 person-years) than during the pandemic period (6.96 outbreaks/1,000,000 person-years) (rate ratio (RR) 0.41; 95% confidence interval (CI) 0.34 to 0.51). According to the aetiology of the outbreak, those of viral aetiology decreased from 7.82 to 3.38 outbreaks/1,000,000 person-years (RR 2.31; 95% CI 1.72 to 3.12), and those of bacterial aetiology decreased from 5.01 to 2.78 outbreaks/1,000,000 person-years (RR 1.80; 95% CI 1.29 to 2.52). There was a great reduction in AGE outbreaks in Catalonia. This reduction may have been due to the effect of the nonpharmaceutical measures applied to reduce the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the collapse of the healthcare system and epidemiological surveillance services may also have had a strong influence.

Impact of the COVID-19 pandemic on contact tracing of patients with pulmonary tuberculosis.

BACKGROUND: The COVID-19 pandemic could have negative effects on tuberculosis (TB) control. The objective was to assess the impact of the pandemic in contact tracing, TB and latent tuberculosis infection (LTBI) in contacts of patients with pulmonary TB in Catalonia (Spain). METHODS: Contact tracing was carried out in cases of pulmonary TB detected during 14 months in the pre-pandemic period (1 January 2019 to 28 February 2020) and 14 months in the pandemic period (1 March 2020 to 30 April 2021). Contacts received the tuberculin skin test and/or interferon gamma release assay and it was determined whether they had TB or LTBI. Variables associated with TB or LTBI in contacts (study period and sociodemographic variables) were analyzed using adjusted odds ratio (aOR) and the 95% confidence intervals (95% CI). RESULTS: The pre-pandemic and pandemic periods showed, respectively: 503 and 255 pulmonary TB reported cases (reduction of 50.7%); and 4676 and 1687 contacts studied (reduction of 36.1%). In these periods, the proportion of TB cases among the contacts was 1.9% (84/4307) and 2.2% (30/1381) (P = 0.608); and the proportion of LTBI was 25.3% (1090/4307) and 29.2% (403/1381) (P < 0.001). The pandemic period was associated to higher LTBI proportion (aOR = 1.3; 95% CI 1.1-1.5), taking into account the effect on LTBI of the other variables studied as sex, age, household contact and migrant status. CONCLUSIONS: COVID-19 is affecting TB control due to less exhaustive TB and LTBI case detection. An increase in LTBI was observed during the pandemic period. Efforts should be made to improve detection of TB and LTBI among contacts of TB cases.

Azithromycin to Prevent Pertussis in Household Contacts, Catalonia and Navarre, Spain, 2012-2013.

We retrospectively assessed the effectiveness of azithromycin in preventing transmission of pertussis to a patient's household contacts. We also considered the duration between symptom onset in the primary patient and azithromycin administration. We categorized contacts into 4 groups: those treated within <7 days, 8-14 days, 15-21 days, and >21 days after illness onset in the primary patient. We studied 476 primary index patients and their 1,975 household contacts, of whom 4.5% were later identified as having pertussis. When contacts started chemoprophylaxis within <21 days after the primary patient's symptom onset, the treatment was 43.9% effective. Chemoprophylaxis started >14 days after primary patient's symptom onset was less effective. We recommend that contacts of persons with pertussis begin chemoprophylaxis within <14 days after primary patient's symptom onset.

Mumps: MMR vaccination and genetic diversity of mumps virus, 2007-2011 in Catalonia, Spain.

BACKGROUND: Mumps is a vaccine-preventable disease but outbreaks have been reported in persons vaccinated with two doses of MMR vaccine. The objective was to describe the demographic features, vaccination effectiveness and genetic mumps virus diversity among laboratory-confirmed cases between 2007 and 2011 in Catalonia. METHODS: Cases and outbreaks of mumps notified to the notifiable diseases system of Catalonia between 2007 and 2011 retrospectively registered were included. Public health care centres provided written immunization records to regional public health staff to determine the vaccination history. Saliva and serum specimens were collected from suspected cases for laboratory-confirmation using real-time reverse-transcriptase PCR (rtRT-PCR) or serological testing. Phylogenetic analysis of the complete SH gene (316 nucleotides) and complete coding HN protein (1749 nucleotides) sequences was made. Categorical variables were compared using the Chi-square or Fisher's tests and continuous variables using the Student test. Vaccination effectiveness by number of MMR doses was estimated using the screening method. RESULTS: During the study period, 581 confirmed cases of mumps were notified (incidence rate 1.6 cases/100,000 persons-year), of which 60% were male. Three hundred sixty-four laboratory-confirmed cases were reported, of which 44% were confirmed by rtRT-PCR. Of the 289 laboratory-confirmed cases belonging to vaccination cohorts, 33.5% (97) had received one dose of MMR vaccine and 50% (145) two doses. Based on phylogenetic analyses of 316-nucleotide and 174-nucleotide SH sequences, the viruses belonging to viral genotypes were: genotype G (126), genotype D (23), genotype H (2), genotype F (2), genotype J (1), while one remained uncharacterized. Amino acid differences were detected between circulating strains and the Jeryl Lynn vaccine strains, although the majority of amino acid substitutions were genotype-specific. Fifty-one outbreaks were notified that included 324 confirmed mumps cases. Genotype G was the most frequent genotype detected. The family (35%), secondary schools (25%) and community outbreaks (18%) were the most frequent settings. CONCLUSIONS: Our study shows that genotype G viruses are the most prevalent in Catalonia. Most cases occurred in people who had received two doses of MMR, suggesting inadequate effectiveness of the Jeryl Lynn vaccine strain. The possible factors related are discussed.

[False beliefs about vaccines]. / Falsas creencias sobre las vacunas.

Vaccines are an essential tool for the prevention of infectious diseases. However, false ideas and rumours with no scientific foundation about their possible negative effects may dissuade people from being vaccinated, with the consequent risks for the health of the population. The objective of this article is to evaluate the origin and the arguments of some of the most frequent mistaken ideas and rumours about the possible adverse effects of vaccines. Some clearly established adverse effects are presented, as well as false beliefs about various vaccines and potential harm to health. Vaccines, like any drug, can cause adverse effects, but the possible adverse effects of vaccination programs are clearly lower than their individual (vaccinated) and collective benefits (those vaccinated and those who cannot be vaccinated for medical reasons). The possible adverse effects attributable to vaccines should be detected by powerful and well-structured pharmacovigilance systems.

Pulmonary Infections with Nontuberculous Mycobacteria, Catalonia, Spain, 1994-2014.

In Spain, systematic reporting of pulmonary infections with nontuberculous mycobacteria is not mandatory. Therefore, to determine trends, we retrospectively identified cases for January 1994-December 2014 in Catalonia. Over the 21 years, prevalence increased and was associated with being male. Mycobacterium avium complex and M. abscessus prevalence increased; M. kansasii prevalence decreased.

Arbovirus surveillance: first dengue virus detection in local Aedes albopictus mosquitoes in Europe, Catalonia, Spain, 2015.

Dengue has emerged as the most important viral mosquito-borne disease globally. The current risk of dengue outbreaks in Europe appeared with the introduction of the vector Aedes albopictus mosquito in Mediterranean countries. Considering the increasing frequency of dengue epidemics worldwide and the movement of viraemic hosts, it is expected that new autochthonous cases will occur in the future in Europe. Arbovirus surveillance started in Catalonia in 2015 to monitor imported cases and detect possible local arboviral transmission. During 2015, 131 patients with a recent travel history to endemic countries were tested for dengue virus (DENV) and 65 dengue cases were detected. Twenty-eight patients with a febrile illness were viraemic, as demonstrated by a positive real-time RT-PCR test for DENV in serum samples. Entomological investigations around the viraemic cases led to the detection of DENV in a pool of local Ae. albopictus captured in the residency of one case. The sequence of the DENV envelope gene detected in the mosquito pool was identical to that detected in the patient. Our results show how entomological surveillance conducted around viraemic travellers can be effective for early detection of DENV in mosquitoes and thus might help to prevent possible autochthonous transmission.

Factors influencing the spread of pertussis in households: a prospective study, Catalonia and Navarre, Spain, 2012 to 2013.

We aimed to investigate transmission rates of pertussis in household contacts of cases and factors associated with transmission. A prospective epidemiological study was conducted in 2012 and 2013 to determine the incidence of pertussis among household contacts of reported cases in Catalonia and Navarre, Spain. An epidemiological survey was completed for each case and contact, who were followed for 28 days to determine the source of infection (primary case) and detect the occurrence of secondary cases. Odds ratios (ORs) were used to estimate the effectiveness of vaccination and chemoprophylaxis in preventing new cases, using the formula (1 - OR) × 100. For the 688 primary cases, a total of 2,852 contacts were recorded. The household transmission rate was 16.1% (459/2,852) and rose according to the age (> 18 years) and lack of immunisation of the primary cases, and also the age (0-18 years), family relationship (siblings and children), lack of vaccination and chemoprophylaxis of contacts. Pertussis vaccine effectiveness in preventing new cases was 65.0% (95% confidence interval (CI): 11.6 to 86.2) for full vaccination (≥ 4 doses) and 59.7% (95% CI: -6.8 to 84.8) for incomplete vaccination (< 4 doses). The effectiveness of chemoprophylaxis was 62.1% (95% CI: 40.3 to 75.9). To reduce household transmission, contacts should be investigated to detect further cases and to administer chemoprophylaxis. The current vaccination status of cases and contacts can reduce household transmission.

Risk of tuberculosis among pulmonary tuberculosis contacts: the importance of time of exposure to index cases.

INTRODUCTION: The intensity of exposure to index cases of tuberculosis [TB] may increase the risk of TB in their contacts. The aim was to determine TB risk factors among contacts of TB index cases. METHODS: A cohort study was carried out in the contacts of pulmonary TB cases registered by the epidemiological surveillance network from 01/01/2019 to 06/30/2021. The factors associated with the risk of TB in contacts were determined using the adjusted odds ratio [aOR] and its 95% confidence interval [CI]. RESULTS: From 847 TB cases, 7087 contacts were identified. The prevalence of TB was 2.0% [145/7087] and was higher in < 5 years compared to those ≥ 65 years [4.4% versus 1.2%; p < 0.001], in those exposed ≥ 6 h daily [4%], and < 6 h daily [1.6%] with respect to weekly exposure of < 6 h [0.7%; p < 0.001]. Those contacts exposed ≥ 6 h daily [aOR= 6.9; 95%CI:2.1-22.1], < 5 years [aOR= 8.3; 95%CI:1.8-37.8] and immigrants [aOR= 1.7; 95%CI:1.1-2.7] had a higher risk of TB. CONCLUSIONS: The risk of TB increases with the time of exposure to the index case and this risk is also higher in < 5 years and immigrants. Contact tracing has a high yield for detecting new cases of TB.

[Validation of the questionnaire on vaccines and hesitancy to be vaccinated in the Spanish Society of Epidemiology]. / Validación del cuestionario sobre vacunas y reticencia a vacunarse en la Sociedad Española de Epidemiología.

OBJECTIVE: To develop and validate a survey aimed at epidemiologists to measure factors associated with vaccine reluctance. METHOD: Vaccination hesitancy refers to delayed acceptance or refusal of vaccination despite the availability of vaccination services. WHO included vaccination hesitancy among the 10 global health threats in 2019. Within this conceptual framework proposed by WHO, a committee of six experts from the Spanish Society of Epidemiology (SEE) designed a self-administered questionnaire to study factors associated with vaccination hesitancy in epidemiologists. This questionnaire was approved by the SEE Board, and was sent online to all members in 2019. Based on the responses obtained, the following characteristics were validated: face validity, internal validity, construct validity, criterion validity, reliability, as well as the characteristic curves of each item and the information function per item and overall. RESULTS: The final questionnaire showed two well-defined components, perception of vaccines and confidence in the transparency of vaccine data with high degrees of fit in all aspects of validation. Both components have shown that the higher the reluctance to vaccinate the better the questionnaire reports on these aspects. CONCLUSIONS: The study has allowed the development of a validated instrument in Spanish to measure the factors associated with vaccine reluctance among epidemiologists.

Factors Associated with Treatment Prescription to Pulmonary Tuberculosis Contacts in Catalonia (2019-2021): A Population-Based Epidemiological Study.

In countries with low tuberculosis (TB) incidence, the systematic testing and treatment of latent TB infection (LTBI) in contacts of pulmonary TB index cases is the standard of care. The objective of this study, conducted in Catalonia over 2019-2021, was to assess the factors associated with LTBI treatment prescription to close contacts of pulmonary TB index cases. In this population-based epidemiological study of LTBI prevalence among pulmonary TB contacts between 2019 and 2021, multiple logistic backward stepwise regression was used to identify the factors associated with treatment prescription, for which the adjusted odds ratio (aOR) and 95% confidence intervals (CI) were calculated. A total of 1487 LTBI contacts of 542 pulmonary TB index cases were studied, 80.6% of whom received a prescription. The factors associated with LTBI treatment prescription were exposure ≥6 h/day (aOR 14.20; 95% CI 5.22-38.66) and exposure <6 h/day (aOR 7.32, 95% CI 2.48-21.64), whereas the factors associated with no LTBI treatment prescription were age ≥55 years (aOR 0.22, 95% CI 0.08-0.64) and bacillus Calmette-Guerin vaccination (aOR 0.38, 95% CI 0.16-0.90). Crucial to LTBI treatment prescription is information on the contact's duration of exposure to pulmonary TB, not only for contacts exposed for ≥6 h/day, but also for contacts with lower daily exposure levels.

Association between soluble angiotensin-converting enzyme 2 in saliva and SARS-CoV-2 infection: a cross-sectional study.

This study aimed to investigate the association between saliva soluble angiotensin-converting enzyme 2 (sACE2) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children and adults. We selected a convenience sample of adults with post-acute SARS-CoV-2 infection and their household children living in quarantined family households of the metropolitan Barcelona region (Spain) during the spring 2020 pandemic national lockdown. Participants were tested for saliva sACE2 quantification by western blot and nasopharyngeal SARS-CoV-2 RT-PCR detection. A total of 161 saliva samples [82 (50.9%) from children; 79 (49.1%) from females] yielded valid western blot and RT-PCR results. Saliva sACE2 was detected in 79 (96.3%) children and 76 (96.2%) convalescent adults. Twenty (24.4%) children and 20 (25.3%) convalescent adults were positive for SARS-CoV-2 in nasopharynx by RT-PCR. SARS-CoV-2 RT-PCR-negative children had a significantly higher mean proportional level of saliva sACE2 (0.540 × 10-3%) than RT-PCR-positive children (0.192 × 10-3%, p < 0.001) and convalescent adults (0.173 × 10-3%, p < 0.001). In conclusion, children negative for nasopharyngeal SARS-CoV-2 RT-PCR appear to exhibit a higher concentration of saliva sACE2 than SARS-CoV-2 RT-PCR-positive children and convalescent adults. Release of adequate levels of sACE2 in saliva could play a protective role against SARS-CoV-2.

Pandemic A/H1N1 influenza: transmission of the first cases in Spain.

INTRODUCTION: Pandemic A/H1N1 influenza emerged in Mexico at the end of March 2009. Since then, it is still important to provide evidences that contributed to the international spread of the virus and to ascertain the attack rate of this new strain of influenza among the first cases in Spain that led to identify the first transmission in Europe. METHODS: Three pandemic A/H1N1 influenza groups related to an overseas flight were studied: 71 student group, 94 remaining passengers, and 68 contacts of confirmed cases. The attack rate with their 95% confidence interval (CI) among the student group and contacts was calculated. On April 26th, when the first cases were notified, strong preventive measures were implemented among the student group and the contacts of the confirmed cases. RESULTS: On 27th April, the first pandemic A/H1N1 influenza cases confirmed in Spain were three students that came back from Mexico by airplane. A student generated the first native case in Spain and one of the first cases in Europe. Similar attack rates were found between the student group (14.1%; CI: 12.1-16.1) and their contacts (13.2%; CI: 4.4-22.0), but no cases among remaining passengers were detected, suggesting low transmission risk during air travel. CONCLUSION: The first cases of pandemic A/H1N1 influenza in Spain were imported by airplane from Mexico. Preventive efforts to reduce the impact of the influenza influenced that primary and secondary rates were lower than first estimations by WHO.

[Towards COVID-19 control through vaccination: obstacles, challenges and opportunities. SESPAS Report 2022]. / Hacia el control de la COVID-19 a través de la vacunación: obstáculos, desafíos y oportunidades. Informe SESPAS 2022.

In Spain, the vaccination program began in a context of high transmission and low availability of vaccines. The objective of this article is to review the vaccination program against COVID-19 in Europe (3/03/2022) and assess the obstacles, challenges and opportunities posed by the control of this disease. Five vaccines are currently available in Europe: two based on mRNA technology (Comirnaty® and Spikevax®); two based on a non-replicative vector (Vaxzevria® and Janssen); and another based on subunit S (Novavax®). Health authorities have developed comprehensive vaccination strategies prioritizing the prevention of hospitalizations and deaths. In January 2022, 90% of the population was exceeded with full vaccination and 95% coverage in people over 50 years of age. The new challenge is to achieve similar coverage in the rest of the age groups. Vaccination in children and adolescents has become a priority due to the educational and social implications derived from COVID-19 in this population. Communication strategies must be renewed and access barriers eliminated to achieve good coverage. In Spain, studies have been published that find a high effectiveness of vaccination. The main strategy for controlling the pandemic and recovering social activity is the vaccination, but everything indicates that very high levels of vaccination coverage will be necessary and to follow with the non-pharmaceutical measures. In a globalized world, COVID-19 control will only be achieved with a coordinated global strategy and technical and economic support for the vaccination strategy in resource-poor countries.

Outbreaks of Gastroenteritis Due to Norovirus in Schools and Summer Camps in Catalonia, 2017-2019.

We studied outbreaks of acute gastroenteritis due to norovirus in schools and summer camps during 2017-2019 in Catalonia (Spain). The overall attack rate was 21.27% in schools and 33.42% in summer camps (RR 0.64 [95% CI 0.58-0.70]) and 52.63% of outbreaks occurred in cold months and 47.37% in warm months. The mean delay in reporting was 5.61 days (SD 5.58 days) and the mean duration was 6.11 days (SD 6.08 days), with a Pearson correlation coefficient of 0.84 (P < 0.001) between these variables. In outbreaks with person-to-person transmission, the aOR was higher the longer the delay in reporting: 3.07 (95% CI 1.21-7.81) when the delay was 5-8 days and 3.81 when it was >9 days (95% CI 1.42-10.23). The cold months posed a higher risk than the warm months. In common source outbreaks the risk was higher in children in secondary-higher education and in summer camps. IMPORTANCE Norovirus is the main cause of viral acute gastroenteritis outbreaks worldwide. The low infectious dose and the lack of long-term immunity in infected persons means that norovirus often causes outbreaks in institutions and closed and semiclosed centers. Norovirus gastroenteritis are usually mild, with no complications, but occasionally can result in hospital admission. Understanding the risk factors involved in a norovirus outbreak can reduce the spread, severity, and duration of the outbreak and, when a vaccine becomes available, this understanding would help us identify the population groups need to get vaccinated. Here, we show the outbreaks due to norovirus in schools and summer camps, the correlation between the delay in reporting and duration of outbreaks and the relationship of the attack rate and the size of the groups.

SARS-CoV-2 outbreak in a nursing home after vaccination with BNT162b2: A role for the quantification of circulating antibodies.

We describe an outbreak of SARS-CoV-2 (B.1.351) in a nursing home. At the outbreak onset 96% of residents and 76% of HCW had received two doses of BNT162b2. Twenty-eight residents (28/53) and six HCW (6/33) were infected. Infected residents had lower levels of anti-S antibodies compared to those who were not infected (157 vs 552 U/mL). Among 50 residents with available serological status, nineteen (19/25) with serum concentration < 300 U/mL and seven (7/25) with concentration > 300 U/mL acquired SARS-CoV-2 (RR 2.7 [95 %CI 1.4-5.3]). The quantification of circulating antibodies could be useful in detecting people with an impaired immune response who are at high risk of acquiring and spreading SARS-CoV-2.

Impact of COVID-19 Lockdown on the Nasopharyngeal Microbiota of Children and Adults Self-Confined at Home.

The increased incidence of COVID-19 cases and deaths in Spain in March 2020 led to the declaration by the Spanish government of a state of emergency imposing strict confinement measures on the population. The objective of this study was to characterize the nasopharyngeal microbiota of children and adults and its relation to SARS-CoV-2 infection and COVID-19 severity during the pandemic lockdown in Spain. This cross-sectional study included family households located in metropolitan Barcelona, Spain, with one adult with a previous confirmed COVID-19 episode and one or more exposed co-habiting child contacts. Nasopharyngeal swabs were used to determine SARS-CoV-2 infection status, characterize the nasopharyngeal microbiota and determine common respiratory DNA/RNA viral co-infections. A total of 173 adult cases and 470 exposed children were included. Overall, a predominance of Corynebacterium and Dolosigranulum and a limited abundance of common pathobionts including Haemophilus and Streptococcus were found both among adults and children. Children with current SARS-CoV-2 infection presented higher bacterial richness and increased Fusobacterium, Streptococcus and Prevotella abundance than non-infected children. Among adults, persistent SARS-CoV-2 RNA was associated with an increased abundance of an unclassified member of the Actinomycetales order. COVID-19 severity was associated with increased Staphylococcus and reduced Dolosigranulum abundance. The stringent COVID-19 lockdown in Spain had a significant impact on the nasopharyngeal microbiota of children, reflected in the limited abundance of common respiratory pathobionts and the predominance of Corynebacterium, regardless of SARS-CoV-2 detection. COVID-19 severity in adults was associated with decreased nasopharynx levels of healthy commensal bacteria.

Epidemiological analysis of severe hospitalized 2009 pandemic influenza A (H1N1) cases in Catalonia, Spain.

From 25th April 2009 to 20th January 2010, 771 laboratory confirmed cases of 2009 pandemic influenza A (H1N1) were admitted to intensive care units (ICU) or hospitalized in medical wards with clinical criteria of severe disease (hospitalized pneumonias, multiorganic failure, septic shock or admitted to ICU or death while hospitalized). 82% of cases were hospitalized between epidemiological week 43 and 48 (25th October - 5th December 2009). Median age of patients was 40 years (range 0-89 years) and 56% were males. 38.7% cases were in the 15-44 year age-group, 29.4% in the 45-64 and 21.8% were children under 15 years of age. 36.8% were admitted to an ICU and 48 died. Underlying conditions were absent in 29% of patients (up to 38% among those under 15 years old). Differences in the prevalence of underlying conditions were found between children and adults. In children less than 15 years old, asthma (16.2%), other respiratory diseases (12.7%), cognitive disorders (10.2%), epilepsy (8.7%) and neuromuscular disorders (7.1%) were the most frequent. In adults, chronic obstructive pulmonary disease (14.8%), cardiovascular diseases (12.6%), asthma (11.5%), diabetes (11.2%) and morbid obesity (10.6%) were the most frequent. Further surveillance is needed to better characterize the epidemiology of this pandemic.

Hepatitis A outbreaks in the vaccination era in Catalonia, Spain.

Hepatitis A outbreaks have a major impact on public health services and involve case investigation and intervention measures to susceptible contacts. At the end of 1998 a universal vaccination program with a combined hepatitis A+B vaccine was started in Catalonia (Spain) in 12-years-old preadolescents. The objective of this study was to compare the characteristics of hepatitis A outbreaks in the periods before and after the introduction of the preadolescent vaccination program and to estimate the preventable fraction of cases associated to outbreaks. The incidence rates of outbreaks, cases and hospitalization associated with each outbreak were calculated. Two periods were considered: before (1991-1998) and after (2000-2007) the introduction of mass vaccination. The preventable fraction and 95% confidence intervals (CI) of cases associated with outbreaks was calculated. The rate of associated cases with outbreaks was higher in the period before the vaccination program than in the post vaccination period (1.53 per 100,000 person-year vs 1.12 ; p< 0.001), but the rate of hospitalization was greater in the period after the introduction of vaccination program than in the period previous to vaccination (0.70 per million persons-year vs 0.08; p< 0.001). The preventable fraction of cases associated to outbreaks was 19.6%(95%CI 6.7-32.5) in the 0-4 years group and 16.7% (95% CI 6.0-27.5) in the 5-14 years group, but the highest figure (38.6%; 95%CI 21.3-55.9) was observed in the 15-24 years age group. The estimated proportion of cases associated with outbreaks that would theoretically have been prevented with the vaccination program suggests that substantial benefits have been obtained in Catalonia in people aged less than 25 years.