Vaccine effectiveness in reducing COVID-19-related hospitalization after a risk-age-based mass vaccination program in a Chilean municipality: A comparison of observational study designs.

BACKGROUND: Case-control studies involving test-negative (TN) and syndrome-negative (SN) controls are reliable for evaluating influenza and rotavirus vaccine effectiveness (VE) during a random vaccination process. However, there is no empirical evidence regarding the impact in real-world mass vaccination campaigns against SARS-CoV-2 using TN and SN controls. OBJECTIVE: To compare in the same population the effectiveness of SARS-CoV-2 vaccination on COVID-19-related hospitalization rates across a cohort design, TN and SN designs. METHOD: We conducted an unmatched population-based cohort, TN and SN case-control designs linking data from four data sources (public primary healthcare system, hospitalization registers, epidemiological surveillance systems and the national immunization program) in a Chilean municipality (Rancagua) between March 1, 2021 and August 31, 2021. The outcome was COVID-19-related hospitalization. To ensure sufficient sample size in the unexposed group, completion of follow-up in the cohort design, and sufficient time between vaccination and hospitalization in the case-control design, VE was estimated comparing 8-week periods for each individual. RESULTS: Among the 191,505 individuals registered in the primary healthcare system of Rancagua in Chile on March 1, 2021; 116,453 met the cohort study's inclusion criteria. Of the 9,471 hospitalizations registered during the study period in the same place, 526 were COVID-19 cases, 108 were TN controls, and 1,628 were SN controls. For any vaccine product, the age- and sex-adjusted vaccine effectiveness comparing fully and nonvaccinated individuals was 67.2 (55.7-76.3) in the cohort design, whereas it was 67.8 (44.1-81.4) and 77.9 (70.2-83.8) in the TN and SN control designs, respectively. CONCLUSION: The VE of a COVID-19 vaccination program based on age and risk groups tended to differ across the three observational study designs. The SN case-control design may be an efficient option for evaluating COVID-19 VE in real-world settings.

Humoral immunity against SARS-CoV-2 evoked by heterologous vaccination groups using the CoronaVac (Sinovac) and BNT162b2 (Pfizer/BioNTech) vaccines in Chile.

Introduction: Severe acute respiratory syndrome virus 2 (SARS-CoV-2) has caused over million deaths worldwide, with more than 61,000 deaths in Chile. The Chilean government has implemented a vaccination program against SARS-CoV-2, with over 17.7 million people receiving a complete vaccination scheme. The final target is 18 million individuals. The most common vaccines used in Chile are CoronaVac (Sinovac) and BNT162b2 (Pfizer-Biotech). Given the global need for vaccine boosters to combat the impact of emerging virus variants, studying the immune response to SARS-CoV-2 is crucial. In this study, we characterize the humoral immune response in inoculated volunteers from Chile who received vaccination schemes consisting of two doses of CoronaVac [CoronaVac (2x)], two doses of CoronaVac plus one dose of BNT162b2 [CoronaVac (2x) + BNT162b2 (1x)], and three doses of BNT162b2 [BNT162b2 (3x)]. Methods: We recruited 469 participants from Clínica Dávila in Santiago and the Health Center Víctor Manuel Fernández in the city of Concepción, Chile. Additionally, we included participants who had recovered from COVID-19 but were not vaccinated (RCN). We analyzed antibodies, including anti-N, anti-S1-RBD, and neutralizing antibodies against SARS-CoV-2. Results: We found that antibodies against the SARS-CoV-2 nucleoprotein were significantly higher in the CoronaVac (2x) and RCN groups compared to the CoronaVac (2x) + BNT162b2 (1x) or BNT162b2 (3x) groups. However, the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups exhibited a higher concentration of S1-RBD antibodies than the CoronaVac (2x) group and RCN group. There were no significant differences in S1-RBD antibody titers between the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups. Finally, the group immunized with BNT162b2 (3x) had higher levels of neutralizing antibodies compared to the RCN group, as well as the CoronaVac (2x) and CoronaVac (2x) + BNT162b2 (1x) groups. Discussion: These findings suggest that vaccination induces the secretion of antibodies against SARS-CoV-2, and a booster dose of BNT162b2 is necessary to generate a protective immune response. In the current state of the pandemic, these data support the Ministry of Health of the Government of Chile's decision to promote heterologous vaccination as they indicate that a significant portion of the Chilean population has neutralizing antibodies against SARS-CoV-2.

Profilaxis de enfermedad de Chagas en niños y adultos sometidos a trasplante de órganos sólidos y de precursores hematopoyéticos / Prophylaxis against Chagas disease in pediatric and adult patients undergoing solid organ and hematopoietic stem cells transplantation

Chagas disease is a zoonosis caused by T. cruzi. The estimated prevalence in endemic areas is 0.6-0.9 / 100,000. In immunocompromised behaves as an opportunistic pathogen highly aggressive and can evolve with meningoencephalitis, myocarditis or systemic disease. We recommend obtaining serology for all donor and recipient of SOT and HSCT. An infected donor should be discarded as such. In the case of D (-) R (+) exists controversy between prophylaxis and pre emptive therapy. The chosen drug for prophylaxis is nifurtimox for 3 months, effective but with relevant adverse effects. Monitoring should be done with RPC and MicroStrout weekly until six months post-transplant, then on a monthly basis for the duration of immunosuppression and continued for life clinical monitoring (C3).

La enfermedad de Chagas es una zoonosis producida por T. cruzi. La prevalencia estimada en áreas endémicas es de 0,6-0,9/100.000 habitantes . En inmunocomprome-tidos se comporta como un patógeno oportunista de alta agresividad, pudiendo evolucionar con cuadros meningo-encefálicos, miocárdicos o sistémicos. Se recomienda obtener serología para todo donante y receptor de TOS y TPH. Un donante infectado se descarta como tal. En caso de D (-) R (+) existe controversia entre realizar proilaxis o vigilancia más terapia anticipada. La proilaxis aceptada es con nifurtimox por tres meses, efectiva pero con efectos adversos importantes. El seguimiento debe realizarse con RPC y MicroStrout semanal hasta los seis meses post-trasplante; luego, en forma mensual mientras dure la inmunosupresión y continuar de por vida la vigilancia clínica (C3).

[Prophylaxis against Chagas disease in pediatric and adult patients undergoing solid organ and hematopoietic stem cells transplantation]. / Profilaxis de enfermedad de Chagas en niños y adultos sometidos a trasplante de órganos sólidos y de precursores hematopoyéticos.

Chagas disease is a zoonosis caused by T. cruzi. The estimated prevalence in endemic areas is 0.6-0.9 / 100,000. In immunocompromised behaves as an opportunistic pathogen highly aggressive and can evolve with meningoencephalitis, myocarditis or systemic disease. We recommend obtaining serology for all donor and recipient of SOT and HSCT. An infected donor should be discarded as such. In the case of D (-) R (+) exists controversy between prophylaxis and pre emptive therapy. The chosen drug for prophylaxis is nifurtimox for 3 months, effective but with relevant adverse effects. Monitoring should be done with RPC and MicroStrout weekly until six months post-transplant, then on a monthly basis for the duration of immunosuppression and continued for life clinical monitoring (C3).

[Influenza-A as etiology of fever and respiratory insufficiency in adults hospitalized during an outbreak in Chile]. / Reconocimiento de influenza-A como etiología de síndrome febril e insuficiencia respiratoria en adultos hospitalizados durante brote en la comunidad.

BACKGROUND: Influenza-A (IA) occurs every winter, is mostly observed among outpatients. AIM: To describe the clinical and epidemiological characteristics of cases that required hospital admission during an outbreak in Chile in 1999. PATIENTS AND METHODS: Adults subjects, with Influenza A confirmed by antigen detection test, hospitalized in the clinical hospital of the "Hospital Clínico de la Universidad Católica de Chile" between May and June, with fever or respiratory symptoms were studied. A special record was designed to register clinical, microbiological and therapeutic data. RESULTS: Fifty five cases, 26 males, aged 15 to 91 years, were studied. Eighty four percent had chronic concomitant diseases and 9.1% were immunosuppressed. Clinical findings were fever in 873%, asthenia in 83.6%, cough in 93.6%, abnormal pulmonary signs in 69%, an elevated C-reactive protein (mean value of 11.6 +/- 7.1 mg/dL) and acute respiratory insufficiency in 54.5%. Cases were isolated in cohort or individual rooms and 38.2% were admitted to intensive or intermediate care units. Amantadine was prescribed to 52 patients and was well tolerated. Thirty three percent of cases developed pneumonia. These subjects were older; had more dyspnea and respiratory insufficiency than patients without pneumonia. CONCLUSIONS: IA should be borne in mind when dealing with hospitalized adults, during epidemic outbreaks in the community. The clinical picture can resemble a serious bacterial infection. An early diagnosis allows the use of specific treatments, to decrease the risk of nosocomial spread and to avoid unnecessary use of antibiotics.

Coagulase-negative staphylococci: clinical, microbiological and molecular features to predict true bacteraemia.

Coagulase-negative staphylococci (CNS) are frequently isolated from blood cultures, where they may be only a contaminant or the cause of bacteraemia. Determining whether an isolate of CNS represents a true CNS bacteraemia is difficult, and there is no single criterion with sufficient specificity. The aim of this study was to assess those clinical, microbiological, pathogenic and genotypic features that characterize true CNS bacteraemia. Twenty patients having two or more blood cultures positive for CNS and 20 patients with only one positive blood culture were studied. Significant bacteraemia was defined according to clinical and laboratory criteria. Incubation time for blood cultures to become positive, macroscopic appearance of colonies, species determination, biotype, susceptibility to antimicrobials, PFGE pattern and adherence capacity were all studied. Clinical bacteraemia was present in 16/20 patients with two or more positive blood cultures and in 2/20 patients with only one positive blood culture. A significant difference was seen in the median time to positivity between the 18 clinical bacteraemias and 22 contaminations (23.6 versus 29.2 h; P = 0.04, Wilcoxon). There was also a significant difference between the two groups in the median absorbance of the slime test (1.36 versus 0.58; P = 0.005). All significant bacteraemias with two or more positive blood cultures had the same species identified, the same antimicrobial susceptibility pattern and the same PFGE pattern. In two patients with true bacteraemia with only one positive blood culture, the incubation time for the culture to turn positive was <24 h and the slime production absorbance was >2.5. The most useful parameters for the diagnosis of true CNS bacteraemia for patients with two positive blood cultures were incubation time until positive, species identification, antimicrobial susceptibility pattern, slime production and PFGE pattern. For patients with only one blood culture positive for CNS, the useful parameters for prediction of true bacteraemia were incubation time until positive and slime production, both of which are simple, low-cost tests.