Unexpected high mutations detected in new emerging variants of concern (VOCs) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), especially in the case of omicron, raises concerns and efforts to understand their evolutionary trajectory. Several hypotheses have been discussed in literature to conceptualize the source of their emergence, including intra-host viral evolution in immunocompromised patients. These patients grant opportunities for the emergence of new variants through a persisting virus winning against host immunity, and selection for viral mutations driven by treatment interventions. VOCs have in common high mutation rate exceeding the average rate of 1-2 mutations per month. Not many studies have investigated the evolutionary rate of SARS-CoV-2 in immunocompromised candidates. Therefore, the purpose of this study is to reveal potential mechanisms underlying the emergence of VOCs by exploring substitution rate of SARS-CoV-2 genomes from surveyed COVID-19 immunocompromised patient’s studies. First, SARS-CoV-2 genome sequences were collected at sequential time series throughout host infection, which were reported in the previous studies. Filtration criteria was applied to reanalyze patients with prolonged infection documented for ≥ 2 months, and comprehensive sequenced samples for ≥ 6 time points. Then, phylogenetic analysis was conducted using Nextclade (https://clades.nextstrain.org/), followed by mutation rate analysis using two substantial similar approaches to calculate the rate in i) substitutions per month and ii) substitutions per site (per year). The mutation tendency of SARS-CoV-2 in immunocompromised hosts was compared to reported VOCs, particularly to omicron. The highest observed mutation rate accounted for approximately 2.2 mutations per month, which is higher than the average rate. High mutation rate was due to prolonged infection and selection pressure by treatment interventions (i.e., convalescent plasma and antibodies). Here, higher rate of intra-host viral evolution in immunocompromised patients is detected, potentially leading to the emergence of VOC. Hence, this research highlights the need for sequencing efforts in high-risk individuals, updating treatment strategies along with further analysis on adaptive mutants pronounced due to intra-host evolution. Together, such findings provide an ultimate synergy for future public health guidelines and infection control measures.

Parvovirus B19 is a common human pathogen that typically infects erythroid progenitors and causes hematological problems such as anemia and aplastic crises. The clinical presentation depends mainly on the immunological status of the patient. PVB19 can cause serious clinical disorders in immunocompromised patients after transplantation. More than 1500 samples from 90 patients who passed the HSCT in 2015 were tested for the presence of PVB19 in this work. This work describes the incidence of the virus and two typical periods of onset of infection in patients after the transplantation. Although several sources report the negative effect of PVB19 infection on the survival of allogeneic graft patients, this work did not confirm this assertion. Also, the results of this work suggest that allogenic grafts are not the main source for transmission, but that it is likely to be reactivated after long-term persistent or latent PVB19 infections. PVB19 is divided into 3 genotypes. Genotype 1 is the most widespread, genotype 2 is very rare in Europe for the last 10 years, and genotype 3 occurs mainly in tropical localities. This work as the first describes the distribution of genotypes in the Czech Republic. More than 130 samples from 125 PVB19 positive patients, stored in the Motol University Hospital from 2004...

Made available in DSpace on 2014-07-29T15:25:24Z (GMT). No. of bitstreams: 1 CarolinaRodriguesCosta-2009.pdf: 705821 bytes, checksum: 53ed28c3e9fdc5770d04b7c412384968 (MD5) Previous issue date: 2009-06-02 / Adhesion to host tissues, production of hydrolytic enzymes, the resistance to antifungals and ability to production hyphal interfere in the infectious process caused by Candida. Resistance to azole antifungal agents, used to treatment of candidiasis, has been observed to immunocompromised patients. Molecular typing based on RAPD-PCR has been used to discriminate between susceptible and resistant isolates to antifungal agents. In this work, were evaluated the virulence factors and molecular characteristics of Candida isolates obtained of samples from blood, catheter of nosocomial patients and from oral cavity of HIV positive patients. The isolates were identified as: Candida albicans (59) Candida parapsilosis (22), Candida tropicalis (14) Candida guilliermondii (07), Candida. famata (05), Candida krusei (03), Candid. lusitaniae (01) and Candida kefyr (01). The proteinase and phospholipase production and the adherence ability were determined for these yeasts. The effect of fluconazole and itraconazole antifungal agents on hyphal formation were studied to 5 isolates previously classified as either susceptible or resistant. The characterization genotypic of resistant and susceptible isolates to fluconazole was carried out for 13 isolates of C. albicans by RAPD-PCR method. The results showed that proteinase activity was detected in 88.1% of C. albicans isolates and in 69.8% of non C. albicans, while phospholipase was produced in 55.9% of C. albicans isolates and in 37.7% of non C. albicans. Isolates of blood were more proteolitic than catheter and oral cavity, while for phospholipase, there was more production of this enzyme in the oral cavity. The ability of adherence to buccal epithelial cell was higher in C. albicans than non C. albicans, however there was not behavior difference between the isolates from different sources studied. The hyphal formation was higher in resistant isolates than susceptible isolates when used the both drugs. In RAPD-PCR method the formation of two different groups was verified for susceptible and resistant isolates being that only one resistant isolate was clustered in the susceptible group. Thus, in this work, it was verified that the exoenzymes activity and adherence ability depend not only of the specie of Candida, but too of the source from host; the resistant isolates produced more hyphal than susceptible isolates under the antifungal action and the molecular characteristics of the resistant isolates did not suggest unique DNA fingerprints did not predicting their susceptibility to fluconazole / A capacidade de aderência ao tecido do hospedeiro, a produção de exoenzimas, a resistência aos antifúngicos e a formação de hifas são fatores que podem interferir no processo infeccioso causado por Candida. Resistência aos derivados azólicos utilizados no tratamento de candidíase, tem sido observada em pacientes imunocomprometidos. Tipagem molecular como o RAPD-PCR tem sido utilizada para discriminação entre isolados de Candida spp suscetíveis e resistentes aos antifúngicos. Neste trabalho foram avaliados fatores de virulência e características moleculares de leveduras do gênero Candida isoladas de amostras do sangue, de cateter de pacientes nosocomiais e da cavidade bucal de pacientes HIV positivos. Os isolados utilizados foram identificados como: Candida albicans (59) Candida parapsilosis (22), Candida tropicalis (14) Candida guilliermondii (07), Candida famata (05), Candida krusei (03), Candida lusitaniae (01) e Candida kefyr (01). Estas leveduras foram avaliadas quanto à atividade de proteinase, fosfolipase e à sua capacidade de aderência. A ação do fluconazol e itraconazol sobre a formação hifal, foi avaliada em 5 isolados previamente classificados como suscetíveis e resistentes ao fluconazol e ao itraconazol. A caracterização genotípica de 13 isolados de C albicans resistentes e suscetíveis ao fluconazol foi realizada por meio de RAPD-PCR. Os resultados mostraram que a atividade de proteinase foi detectada em 88,1% de isolados de C. albicans e em 69,8% de Candida não albicans, enquanto que a fosfolipase foi detectada em 55,9% de isolados de C. albicans e em 37,7% de Candida não albicans. Isolados do sangue foram mais proteolíticos do que os do cateter e os da cavidade bucal, enquanto para a fosfolipase foi observado maior produção desta enzima em isolados da cavidade bucal. A capacidade de aderência à célula epitelial foi maior em C. albicans que Candida não albicans, no entanto não houve diferença de comportamento entre isolados obtidos dos diferentes locais estudados. A formação de hifas foi maior nos isolados resistentes do que nos isolados suscetíveis quando sob a ação de qualquer um dos dois fármacos. Na análise do RAPD-PCR foi verificada a formação de dois grupos distintos para os isolados suscetíveis e resistentes ao fluconazol, sendo que apenas um isolado resistente foi agrupado com os suscetíveis. Neste trabalho, foi verificado que a atividade de exoenzimas e a habilidade de aderência dependem além da espécie de Candida como também do local onde foi isolada no hospedeiro, que isolados resistentes formaram mais hifas do que os suscetíveis sob a ação de antifúngico e que as características moleculares dos isolados resistentes em mais de um padrão fingerprinting não permitiram predizer a sua suscetibilidade ao fluconazol

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

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No. of bitstreams: 2 Dissertação - Brunno Câmara Lopes Costa - 2018.pdf: 3761382 bytes, checksum: 9df697870cea1a53a75ea6dad69c9e91 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-08-17 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Human Bocavirus (HBoVs) are classified in the Parvoviridae family and are associated with respiratory and gastrointestinal symptoms. Viral infections are an important cause of morbimortality in immunocompromised patients such as allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. The aim of the present study was to evaluate the positivity rate and loads of HBoVs in clinical samples (feces and sera) of patients who were subjected to allo-HSCT at a reference center for bone marrow transplantation in Goiânia, Goiás. A total of 105 fecal samples and 145 sera samples were collected from 21 consecutive patients, during October 2012 to October 2014. Samples were screened by qPCR TaqMan assay, with specific probe and primers targeting all HBoVs genotypes (HBoV-1 to -4), and viral loads were determined using serial dilutions of a recombinant plasmid, targeting the NP1 gene. The results showed that 53.4% (11/21) of the patients were male, aged between four and 61 years-old (mean 35 years). The most observed hematologic malignancy was myeloid leukemia (acute or chronic), accounting for 57.1% (12/21) of the cases. The HBoVs were detected in 42.9% (9/21) of the patients and 77.7% (7/9) were positive in both fecal and serum samples. The viral load in fecal samples were higher than in the sera samples and a prolonged fecal shedding were observed, with two patterns: one intermittent and another continuous. Of all HBoV positive patients, six (66.6%) had the first positive sample before the transplantation, and a rise of the viral loads after the allo-HSCT occurred when comparing to the loads before the allo-HSCT. Furthermore, on most cases the highest viral loads were detected during the first 100 days after the allo-HSCT. Considering the symptoms presented by the patients, 66.6% (6/9) had diarrhea at the same period of the viral genome detection in feces, but no statistical significance was observed. Three fecal samples were characterized as being HBoV-1, with more than 99% of nucleotide identity among them. The present data shows a high occurrence and loads of HBoVs in allo-HSCT recipients, with first positivity in fecal samples and later viral detection in sera. These results suggest that fecal samples could be the sample of choice in HBoV monitoring of these patients both before and after the transplant. / Os Bocavírus humanos (HBoVs) pertencem à família Parvoviridae e têm sido associados a sintomas respiratórios e gastroentéricos. As infecções virais são uma importante causa de morbimortalidade em pacientes imunocomprometidos, como os pacientes submetidos a transplante alogênico de células progenitoras hematopoiéticas (TACPH). Dados sobre a ocorrência de HBoV nesses pacientes ainda são escassos. Os objetivos deste estudo foram avaliar a frequência e a carga de HBoVs em amostras clínicas (fezes e soro) de pacientes submetidos a TACPH e avaliar as características gerais e sintomas apresentados, e caracterizar as amostras positivas. Foram incluídos no estudo 21 pacientes consecutivos, dos quais foram coletadas 105 amostras fecais e 145 amostras de soro, em um centro de transplante de medula óssea em Goiânia, Goiás, durante o período de outubro de 2012 a outubro de 2014. As amostras foram testadas por qPCR TaqMan®, com sonda e iniciadores específicos para todos os genótipos de HBoVs (HBoV-1 a -4), e a carga viral nas amostras foi determinada pela construção de uma curva padrão de diluições seriadas de um plasmídeo recombinante, contendo como inserto a região NP1. Os resultados mostraram que 53,4% (11/21) dos pacientes eram do sexo masculino, com idade entre quatro e 61 anos de idade (mediana 35 anos). A neoplasia hematológica mais observada foi a leucemia mieloide (aguda e crônica), totalizando 57,1% (12/21) dos casos. Os HBoVs foram detectados em 42,9% (9/21) dos pacientes, sendo que em 77,7% (7/9) desses houve positividade em ambas amostras de soro e fezes. A carga de HBoV nas amostras fecais foi significativamente maior do que nas amostras séricas, sendo observado dois padrões principais de excreção nas fezes, um intermitente e outro contínuo. Dos nove pacientes, seis (66,6%) tiveram a primeira amostra positiva antes de serem submetidos ao transplante, sendo observado aumento nas cargas de HBoV pós-TACPH em comparação às cargas pré-TACPH e, na maioria dos casos, os picos da carga viral foram detectados durante os 100 primeiros dias após o TACPH. Considerando os sintomas apresentados pelos pacientes, 66,6% (6/9) desses apresentavam diarreia no mesmo período da detecção de HBoV nas amostras fecais, porém não houve significância estatística entre a positividade e os sintomas gastroentéricos. Três amostras fecais foram caracterizadas como sendo o genótipo HBoV-1, com mais de 99% de identidade nucleotídica entre elas. Os dados apresentados mostram uma alta ocorrência e elevada carga de HBoVs nos pacientes submetidos ao TACPH, além de detecção inicial nas fezes com posterior positividade no soro. Esses resultados sugerem que as fezes poderiam ser a amostra clínica de escolha para o monitoramento desses pacientes, tanto antes quanto após o transplante.

A refeição de hospital é parte fundamental dos cuidados de pacientes.Uma dieta balanceada pode incentivar pacientes a comer de forma equilibrada dando-lhes os nutrientes que necessitam para se recuperarem em curto prazo de cirurgia ou doença. A irradiação gama é conhecida como o melhor método para destruir tanto os microrganismos patogênicos como os de deterioração, sem comprometer as propriedades nutricionais e a qualidade sensorial dos alimentos. Por conta disto, pode ser um método eficaz para elaboração de refeições apropriadas para pacientes imunodeprimidos. Neste trabalho, pratos prontos contendo arroz, carne grelhada e refogado de cenoura, foram submetidos a doses radapertizantes (30 kGy e 50 kGy) e armazenados a temperatura ambiente por até 90 dias. O tratamento controle permaneceu congelado pelo mesmo período. Os alimentos foram avaliados através de análises físico-química e microbiológicas por método molecular. O teor de umidade dos alimentos permaneceu inalterado por todo o período em todos os tratamentos. A irradiação provocou mudança de cor no arroz, favorecendo um tom amarelado e tornando-se ainda mais acentuado no decorrer do armazenamento. A cenoura teve a coloração caraterística vermelho-alaranjada reduzida com o tempo de armazenamento. No mesmo alimento, a irradiação reduziu o pH e o teor de carotenóides, ao passo que os compostos fenólicos decresceram durante o armazenamento. A carne grelhada conservou sua maciez, mas teve sua coloração alterada para uma tonalidade mais clara. Houve também uma pequena rancificação devido à radiação e também ao período de armazenamento. Por metodologia genônica, bactérias, com predominância dos gêneros Bacillus, Acinetobacter e Enterobacter, foram detectadas nos alimentos controle e até nos irradiados com a dose de 30 kGy. A dose de radiação segura para esterilização foi a de 50 kGy / Hospital food is an essential part of patient care. A good meal can encourage patients to eat well, giving them the nutrients they need to recover from surgery or illness. Gamma irradiation is well known to be the best method for destroying pathogenic and spoilage microorganisms without compromising the nutritional properties and sensory quality of the foods; it is also a method used for preparing foods for immunocompromised patients. In this work, ready-to-eat food containing rice, grilled meat and steamed carrot, was radappertizated with doses of 30 kGy and 50 kGy, and stored at room temperature for 90 days. The control treatment remained frozen for the same period. Analysis by physical-chemical molecular microbiological methods were used. The moisture of the foods remained unchanged through this period, in all treatments. Irradiation caused a yellowing of rice, which became more pronounced during the storage. The characteristic red-orange color of carrots was decreased during storage time. In the same food irradiation reduced the pH and content of carotenoids, while the phenolic compounds declined with the storage. Grilled meat retained its softness, but its color had/was changed to a lighter shade. There was also a small/some rancidity, due to radiation and also to the storage period. By genomic methodology, bacteria, predominantly of the genera Bacillus, Acinetobacter and Enterobacter, were detected in control and even in food irradiated with a dose of 30 kGy. The safe radiation dose for sterilization was 50 kGy.

Gram-negative infection has been linked to hospital water although few studies have examined whether water systems are reservoirs of nosocomial pathogens. This study investigated longitudinal recovery of the opportunistic pathogens Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter baumannii from water outlets of a haematology unit and evaluated Point-Of-Use Filtration (POU-F) as a control measure. In a two-year double cross-over trial, water samples and swabs were taken weekly from 39 showers/taps on the unit. Four study phases alternated between non-filtered (Phases 1 & 3), and filtered outlets (Phases 2 & 4) using Pall AquasafeTM 14-day filters. In Phases 1 & 3; 99% of 1396 samples yielded bacterial growth, with colonies generally too numerous to count. Target species were isolated from 22% of water samples (P. aeruginosa 14%; S. maltophilia 10%) and 10% of swabs. P. aeruginosa was particularly associated with handwash stations and S. maltophilia with showers. A. baumannii was not isolated. With POU-F; 22% of 1242 samples yielded bacterial growth (mean CFU/100ml ,4.6). S. maltophilia was isolated only once from water but never from outlet swabs. PCR typing identified clusters of isolates colonizing different outlets over time but no clear association between water and patient isolates was identified. The incidence of Gram negative infections remained low throughout the study. Without POU-F, water from taps/showers represented a source of bacteria including the target species. POU-F substantially reduced the frequency and number of target species from every outlet, and merits further investigation as an intervention to protect immunocompromised patients from opportunistic pathogens.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 4 uppsatser.

Objetivo: A vacina inativada contra HVA (Havrix) é altamente eficaz e segura em crianças saudáveis. Não há muitos dados disponíveis na literatura sobre a resposta de crianças imunocomprometidas à essa vacina. O objetivo deste estudo foi avaliar a resposta de pacientes pediátricos portadores de Síndrome de Down e de Hepatopatia Crônica à uma vacina inativada contra Hepatite A, comparando suas respostas com as de crianças saudáveis. Casuística e Métodos: Foi realizado um estudo prospectivo, aberto e controlado com 138 crianças e adolescentes, de 1 a 16 anos, suscetíveis à infecção pelo virus A (anti-HVA negativo). Os indivíduos foram divididos em 3 grupos: Grupo I: portadores de Síndrome de Down (n = 49), Grupo II: Hepatopatas Crônicos (n = 34) e Grupo III: controle, composto por crianças saudáveis (n = 55). Todos os indivíduos recebiam 2 doses, nos meses 0 e 6, da vacina Havrix 720 UE , aplicada intramuscular, no deltóide. Um mês após cada dose da vacina, as crianças e os adolescentes eram submetidas à coleta de sangue para realização de titulação de anticorpos anti-HVA. Resultados: As taxas de soroconversão, após a primeira dose da vacina, no mês 1, foram de 92%, 76% e 94% nos grupos I, II e III, respectivamente. Um mês após a segunda dose, as porcentagens de soroconversão foram de 100% x 97% x 100%, para os grupos, na mesma ordem. As médias geométricas dos títulos de anticorpos anti-HVA foram, na primeira e segunda coletas, de 164,02 e 1719,86 mUI/ml nas crianças com Síndrome de Down, de 107,77 e 812,40 mUI/ml nos cirróticos e de 160,77 e 2344,90 mUI/ml, no grupo controle. O grupo dos pacientes cirróticos apresentou diferença estatisticamente significativa em relação às taxas de soroconversão no primeiro mês, após 1 dose da vacina, e aos títulos de anticorpos anti-HVA no final do estudo, quando comparado aos controles saudáveis. Apenas 14% dos indivíduos vacinados apresentaram sintomas locais, como dor e vermelhidão. Cinco porcento apresentaram sintomas gerais. Não ocorreu nenhum efeito adverso sério ou reação imediata à vacina. Os efeitos adversos diminuíram por ocasião da segunda dose.Conclusões: A vacina inativada Havrix, contra Hepatite A, provoca altas taxas de soroconversão e é altamente segura em pacientes pediátricos portadores de Síndrome de Down e de Cirrose. As crianças e adolescentes com Cirrose respondem à vacina inativada anti-HVA com títulos de anticorpos mais baixos do que as crianças saudáveis e do que as portadoras de Síndrome de Down. / Objective: The inactivated hepatitis A vaccine (Havrix) is highly immunogenic and safe in healthy children. However, data about the response of immunocompromised children to this vaccine are not very frequent in the literature. The objective of this study was to assess the response of pediatric patients with Down syndrome and chronic liver disease to an inactivated hepatitis A vaccine, and to compare their responses to those of healthy children. Patients and Methods: A prospective, open-label, controlled study was performed with 138 children and adolescents susceptible to hepatitis A virus (anti-HAV negative) with ages between 1 and 16 years. Patients were divided into three groups: Group I, Down syndrome patients (n = 49); Group II, patients with chronic liver disease (n = 34); and Group III, healthy children/controls (n = 55). All patients and controls received two intramuscular doses of Havrix 720 UE in the deltoid muscle at months 0 and 6. One month after each dose, patients underwent blood collection for the assessment of anti-HAV titers. Results: Seroconversion rates after the first dose (month 1) were 92%, 76%, and 94% in Groups I, II, and III, respectively; one month after the second dose, these percentages were 100%, 97%, and 100%. Geometric mean titers were 164.02 and 1719.86 mUI/ml in the first and second collections for Down syndrome children; 107.77 and 812.40 mUI/ml for cirrhotic patients; and 160.77 and 2344.90 mUI/ml for controls. The group of cirrhotic patients presented a statistically significant difference in seroconversion rates at month 1, and in anti-HAV titers in the end of the study when compared to healthy controls. Only 14% of the vaccinated individuals presented local symptoms, such as pain and redness; 5% presented general symptoms. No severe adverse effects or immediate reaction to the vaccine were observed. The occurrence of adverse reactions was lower in the application of the second dose. Conclusions: The inactivated hepatitis A vaccine (Havrix) presents high rates of seroconversion and is highly safe in pediatric patients with Down syndrome and cirrhosis. Cirrhotic children and adolescents have responded to the inactivated hepatitis A vaccine with lower antibody titers when compared to healthy children and Down syndrome.

Objetivo: A vacina inativada contra HVA (Havrix) é altamente eficaz e segura em crianças saudáveis. Não há muitos dados disponíveis na literatura sobre a resposta de crianças imunocomprometidas à essa vacina. O objetivo deste estudo foi avaliar a resposta de pacientes pediátricos portadores de Síndrome de Down e de Hepatopatia Crônica à uma vacina inativada contra Hepatite A, comparando suas respostas com as de crianças saudáveis. Casuística e Métodos: Foi realizado um estudo prospectivo, aberto e controlado com 138 crianças e adolescentes, de 1 a 16 anos, suscetíveis à infecção pelo virus A (anti-HVA negativo). Os indivíduos foram divididos em 3 grupos: Grupo I: portadores de Síndrome de Down (n = 49), Grupo II: Hepatopatas Crônicos (n = 34) e Grupo III: controle, composto por crianças saudáveis (n = 55). Todos os indivíduos recebiam 2 doses, nos meses 0 e 6, da vacina Havrix 720 UE , aplicada intramuscular, no deltóide. Um mês após cada dose da vacina, as crianças e os adolescentes eram submetidas à coleta de sangue para realização de titulação de anticorpos anti-HVA. Resultados: As taxas de soroconversão, após a primeira dose da vacina, no mês 1, foram de 92%, 76% e 94% nos grupos I, II e III, respectivamente. Um mês após a segunda dose, as porcentagens de soroconversão foram de 100% x 97% x 100%, para os grupos, na mesma ordem. As médias geométricas dos títulos de anticorpos anti-HVA foram, na primeira e segunda coletas, de 164,02 e 1719,86 mUI/ml nas crianças com Síndrome de Down, de 107,77 e 812,40 mUI/ml nos cirróticos e de 160,77 e 2344,90 mUI/ml, no grupo controle. O grupo dos pacientes cirróticos apresentou diferença estatisticamente significativa em relação às taxas de soroconversão no primeiro mês, após 1 dose da vacina, e aos títulos de anticorpos anti-HVA no final do estudo, quando comparado aos controles saudáveis. Apenas 14% dos indivíduos vacinados apresentaram sintomas locais, como dor e vermelhidão. Cinco porcento apresentaram sintomas gerais. Não ocorreu nenhum efeito adverso sério ou reação imediata à vacina. Os efeitos adversos diminuíram por ocasião da segunda dose.Conclusões: A vacina inativada Havrix, contra Hepatite A, provoca altas taxas de soroconversão e é altamente segura em pacientes pediátricos portadores de Síndrome de Down e de Cirrose. As crianças e adolescentes com Cirrose respondem à vacina inativada anti-HVA com títulos de anticorpos mais baixos do que as crianças saudáveis e do que as portadoras de Síndrome de Down. / Objective: The inactivated hepatitis A vaccine (Havrix) is highly immunogenic and safe in healthy children. However, data about the response of immunocompromised children to this vaccine are not very frequent in the literature. The objective of this study was to assess the response of pediatric patients with Down syndrome and chronic liver disease to an inactivated hepatitis A vaccine, and to compare their responses to those of healthy children. Patients and Methods: A prospective, open-label, controlled study was performed with 138 children and adolescents susceptible to hepatitis A virus (anti-HAV negative) with ages between 1 and 16 years. Patients were divided into three groups: Group I, Down syndrome patients (n = 49); Group II, patients with chronic liver disease (n = 34); and Group III, healthy children/controls (n = 55). All patients and controls received two intramuscular doses of Havrix 720 UE in the deltoid muscle at months 0 and 6. One month after each dose, patients underwent blood collection for the assessment of anti-HAV titers. Results: Seroconversion rates after the first dose (month 1) were 92%, 76%, and 94% in Groups I, II, and III, respectively; one month after the second dose, these percentages were 100%, 97%, and 100%. Geometric mean titers were 164.02 and 1719.86 mUI/ml in the first and second collections for Down syndrome children; 107.77 and 812.40 mUI/ml for cirrhotic patients; and 160.77 and 2344.90 mUI/ml for controls. The group of cirrhotic patients presented a statistically significant difference in seroconversion rates at month 1, and in anti-HAV titers in the end of the study when compared to healthy controls. Only 14% of the vaccinated individuals presented local symptoms, such as pain and redness; 5% presented general symptoms. No severe adverse effects or immediate reaction to the vaccine were observed. The occurrence of adverse reactions was lower in the application of the second dose. Conclusions: The inactivated hepatitis A vaccine (Havrix) presents high rates of seroconversion and is highly safe in pediatric patients with Down syndrome and cirrhosis. Cirrhotic children and adolescents have responded to the inactivated hepatitis A vaccine with lower antibody titers when compared to healthy children and Down syndrome.