Severity of influenza illness by seasonal influenza vaccination status among hospitalised patients in four South American countries, 2013-19: a surveillance-based cohort study.

BACKGROUND: Although several studies have reported attenuated influenza illness following influenza vaccination, results have been inconsistent and have focused predominantly on adults in the USA. This study aimed to evaluate the severity of influenza illness by vaccination status in a broad range of influenza vaccine target groups across multiple South American countries. METHODS: We analysed data from four South American countries (Argentina, Brazil, Chile, and Paraguay) participating in REVELAC-i, a multicentre, test-negative design, vaccine effectiveness network including 41 sentinel hospitals. Individuals hospitalised at one of these centres with severe acute respiratory infection were tested for influenza by real-time RT-PCR, and were included in the analysis if they had complete information about their vaccination status and outcomes of their hospital stay. We used multivariable logistic regression weighted by inverse probability of vaccination and adjusted for antiviral use, duration of illness before admission, and calendar week, to calculate the adjusted odds ratios (aORs) of intensive care unit (ICU) admission and in-hospital death (and combinations of these outcomes) among influenza-positive patients by vaccination status for three target groups: young children (aged 6-24 months), adults (aged 18-64 years) with pre-existing health conditions, and older adults (aged ≥65 years). Survival curves were used to compare length of hospital stay by vaccination status in each target group. FINDINGS: 2747 patients hospitalised with PCR-confirmed influenza virus infection between Jan 1, 2013, and Dec 8, 2019, were included in the study: 649 children (70 [10·8%] fully vaccinated, 193 [29·7%] partially vaccinated) of whom 87 (13·4%) were admitted to ICU and 12 (1·8%) died in hospital; 520 adults with pre-existing medical conditions (118 [22·7%] vaccinated), of whom 139 (26·7%) were admitted to ICU and 55 (10·6%) died in hospital; and 1578 older adults (609 [38·6%] vaccinated), of whom 271 (17·2%) were admitted to ICU and 220 (13·9%) died in hospital. We observed earlier discharge among partially vaccinated children (adjusted hazard ratio 1·14 [95% CI 1·01-1·29]), fully vaccinated children (1·24 [1·04-1·47]), and vaccinated adults with pre-existing medical conditions (1·78 [1·18-2·69]) compared with their unvaccinated counterparts, but not among vaccinated older adults (0·82 [0·65-1·04]). Compared with unvaccinated individuals, lower odds of ICU admission were found for partially vaccinated children (aOR 0·64 [95% CI 0·44-0·92]) and fully vaccinated children (0·52 [0·28-0·98]), but not for adults with pre-existing conditions (1·25 [0·93-1·67]) or older adults (0·88 [0·72-1·08]). Lower odds of in-hospital death (0·62 [0·50-0·78]) were found in vaccinated versus unvaccinated older adults, with or without ICU admission, but did not differ significantly in partially vaccinated (1·35 [0·57-3·20]) or fully vaccinated young children (0·88 [0·16-4·82]) or adults with pre-existing medical conditions (1·09 [0·73-1·63]) compared with the respective unvaccinated patient groups. INTERPRETATION: Influenza vaccination was associated with illness attenuation among those hospitalised with influenza, although results differed by vaccine target group. These findings might suggest that attenuation of disease severity might be specific to certain target groups, seasons, or settings. FUNDING: US Centers for Disease Control and Prevention. TRANSLATIONS: For the Spanish and Portuguese translations of the abstract see Supplementary Materials section.

Effectiveness of mRNA-1273, BNT162b2, and BBIBP-CorV vaccines against infection and mortality in children in Argentina, during predominance of delta and omicron covid-19 variants: test negative, case-control study.

OBJECTIVE: To estimate the effectiveness of a two dose vaccine schedule (mRNA-1273, BNT162b2, and BBIBP-CorV) against SARS-CoV-2 infection and covid-19 related death and short term waning of immunity in children (3-11 years old) and adolescents (12-17 years old) during periods of delta and omicron variant predominance in Argentina. DESIGN: Test negative, case-control study. SETTING: Database of the National Surveillance System and the Nominalized Federal Vaccination Registry of Argentina. PARTICIPANTS: 844 460 children and adolescents without previous SARS-CoV-2 infection eligible to receive primary vaccination schedule who were tested for SARS-CoV-2 by polymerase chain reaction or rapid antigen test from September 2021 to April 2022. After matching with their corresponding controls, 139 321 (60.3%) of 231 181 cases remained for analysis. EXPOSURES: Two dose mRNA-1273, BNT162b2, and BBIBP-CorV vaccination schedule. MAIN OUTCOME MEASURES: SARS-CoV-2 infection and covid-19 related death. Conditional logistic regression was used to estimate the odds of SARS-CoV-2 infection among two dose vaccinated and unvaccinated participants. Vaccine effectiveness was estimated as (1-odds ratio)×100%. RESULTS: Estimated vaccine effectiveness against SARS-CoV-2 infection was 61.2% (95% confidence interval 56.4% to 65.5%) in children and 66.8% (63.9% to 69.5%) in adolescents during the delta dominant period and 15.9% (13.2% to 18.6%) and 26.0% (23.2% to 28.8%), respectively, when omicron was dominant. Vaccine effectiveness declined over time, especially during the omicron period, from 37.6% (34.2% to 40.8%) at 15-30 days after vaccination to 2.0% (1.8% to 5.6%) after ≥60 days in children and from 55.8% (52.4% to 59.0%) to 12.4% (8.6% to 16.1%) in adolescents.Vaccine effectiveness against death related to SARS-CoV-2 infection during omicron predominance was 66.9% (6.4% to 89.8%) in children and 97.6% (81.0% to 99.7%) in adolescents. CONCLUSIONS: Vaccine effectiveness in preventing mortality remained high in children and adolescents regardless of the circulating variant. Vaccine effectiveness in preventing SARS-CoV-2 infection in the short term after vaccination was lower during omicron predominance and decreasing sharply over time. TRIAL REGISTRATION: National Registry of Health Research IS003720.

Effectiveness of rAd26-rAd5, ChAdOx1 nCoV-19, and BBIBP-CorV vaccines for risk of infection with SARS-CoV-2 and death due to COVID-19 in people older than 60 years in Argentina: a test-negative, case-control, and retrospective longitudinal study.

BACKGROUND: In January, 2021, a vaccination campaign against COVID-19 was initiated with the rAd26-rAd5, ChAdOx1 nCoV-19, and BBIBP-CorV vaccines in Argentina. The objective of this study was to estimate vaccine effectiveness at reducing risk of SARS-CoV-2 infection and COVID-19 deaths in people older than 60 years. METHODS: In this test-negative, case-control, and retrospective longitudinal study done in Argentina, we evaluated the effectiveness of three vaccines (rAd26-rAd5, ChAdOx1 nCoV-19, and BBIBP-CorV) on SARS-CoV-2 infection and risk of death in people with RT-PCR confirmed COVID-19, using data from the National Surveillance System (SNVS 2.0). All individuals aged 60 years or older reported to SNVS 2.0 as being suspected to have COVID-19 who had disease status confirmed with RT-PCR were included in the study. Unvaccinated individuals could participate in any of the analyses. People with suspected COVID-19 who developed symptoms before the start of the implementation of the vaccination programme for their age group or district were excluded from the study. The odds ratio of SARS-CoV-2 infection was evaluated by logistic regression and the risk of death in individuals with RT-PCR confirmed COVID-19 was evaluated by proportional hazard regression models, adjusted for possible confounders: age at the time of the symptom onset date, sex, district of residence, epidemiological week corresponding to the symptom onset date, and history of COVID-19. The estimation of vaccine effectiveness to prevent death due to COVID-19 was done indirectly by combining infection and death estimates. In addition, we evaluated the effect of the first dose of viral vector vaccines across time. FINDINGS: From Jan 31, to Sept 14, 2021, 1 282 928 individuals were included, of whom 687 167 (53·6%) were in the rAd26-rAd5 analysis, 358 431 (27·6%) in the ChAdOx1 nCoV-19 analysis, and 237 330 (18·5%) in the BBIBP-CorV analysis. Vaccine effectiveness after two doses was high for all three vaccines, adjusted odds ratio 0·36 (95% CI 0·35-0·37) for rAd26-rAd5, 0·32 (0·31-0·33) for ChAdOx1 nCoV-19, and 0·56 (0·55-0·58) for BBIBP-CorV. After two doses, the effect on deaths was higher than that on risk of infection: adjusted hazard ratio 0·19 (95% CI 0·18-0·21) for rAd26-rAd5, 0·20 (0·18-0·22) for ChAdOx1 nCoV-19, and 0·27 (0·25-0·29) for BBIBP-CorV. The indirectly estimated effectiveness on deaths was 93·1% (95% CI 92·6-93·5) for rAd26-rAd5, 93·7% (93·2-94·3) for ChAdOx1 nCoV-19, and 85·0% (84·0-86·0) for BBIBP-CorV following two doses. First dose effect of viral vector vaccines remained stable over time. INTERPRETATION: The vaccines used in Argentina showed effectiveness in reducing infection and death by SARS-CoV-2 and COVID-19. FUNDING: None.

All-cause excess mortality during the COVID-19 pandemic in Argentina, 2020 / Exceso de mortalidad por todas las causas en el contexto de la pandemia de covid-19 en argentina, 2020

RESUMEN INTRODUCCIÓN: La vigilancia del exceso de mortalidad (EM) por todas las causas puede ser utilizada para evaluar la magnitud del impacto de la pandemia de la enfermedad por el coronavirus 2019 (COVID-19, por sus siglas en inglés). El objetivo de este estudio fue calcular el EM en Argentina durante 2020 y compararlo con las muertes por COVID-19 notificadas en el Sistema Nacional de Vigilancia de la Salud (SNVS). MÉTODOS: Se realizó un estudio descriptivo, en el que se analizaron las series de defunciones por todas las causas de los períodos 2015-2019 y 2020, y las muertes por COVID-19 notificadas al SNVS durante 2020. El EM se estableció como la diferencia entre el número de defunciones por todas las causas del año 2020 y el umbral de alerta (percentil 75 de los datos históricos). Se calculó la proporción de muertes en exceso no explicadas por los casos confirmados de COVID-19 fallecidos. RESULTADOS: En 2020 el EM en Argentina fue de 10,6% (36 306 muertes sobre el umbral). En el primer semestre no hubo exceso, las muertes observadas se encontraron por debajo del límite inferior esperado; en el segundo semestre fue de 25,6% por encima del umbral. Se notificaron 45 568 fallecidos por COVID-19 mediante el SNVS. DISCUSIÓN: Los valores de mortalidad concuerdan con la evolución de la pandemia en el país. El sistema de notificación de fallecidos por COVID-19 es robusto debido al aporte de una amplia red y al cotejo con otras fuentes oficiales para completar la información en el SNVS.

ABSTRACT INTRODUCTION: All-cause excess mortality (EM) surveillance can be used to assess the impact of the COVID-19 pandemic. The aim of this study was to estimate the EM in Argentina in 2020 and compare it with the deaths from COVID-19 reported in the National Health Surveillance System (SNVS). METHODS: A descriptive study was conducted based on the analysis of all-cause mortality series for the period 2015-2019,2020 and confirmed COVID-19 deaths during 2020 in Argentina. The EM was calculated as the difference between the number of deaths in 2020 and the alert threshold (75th percentile of historical data). The proportion of excess deaths not explained by deaths reported by COVID-19 in the surveillance system was calculated. RESULTS: EM in Argentina in 2020 was 10.6% (36306 deaths above the threshold). In the first half of the year there was no excess, deaths were below the expected lower limit; in the second half of the year it was 25.6% above the threshold. A total of45568 COVID-19 deaths were reported to the SNVS. DISCUSSION: Mortality values are in accordance with the evolution of the pandemic in the country. The COVID-19 death reporting system is robust due to the contribution of a wide notification network and the cross-checking with other official sources to complete the information in the SNVS.

Exceso de mortalidad por todas las causas en el contexto de la pandemia del COVID-19 en Argentina, 2020 / All-cause excess mortality during the COVID-19 pandemic in Argentina, 2020

INTRODUCCIÓN: La vigilancia del exceso de mortalidad (EM) por todas las causas puede ser utilizada para evaluar la magnitud del impacto de la pandemia de la enfermedad por el coronavirus 2019 (COVID-19, por sus siglas en inglés). El objetivo de este estudio fue calcular el EM en Argentina durante 2020 y compararlo con las muertes por COVID-19 notificadas en el Sistema Nacional de Vigilancia de la Salud (SNVS). MÉTODOS: Se realizó un estudio descriptivo, en el que se analizaron las series de defunciones por todas las causas de los períodos 2015-2019 y 2020, y las muertes por COVID-19 notificadas al SNVS durante 2020. El EM se estableció como la diferencia entre el número de defunciones por todas las causas del año 2020 y el umbral de alerta (percentil 75 de los datos históricos). Se calculó la proporción de muertes en exceso no explicadas por los casos confirmados de COVID-19 fallecidos. RESULTADOS: En 2020 el EM en Argentina fue de 10,6% (36 306 muertes sobre el umbral). En el primer semestre no hubo exceso, las muertes observadas se encontraron por debajo del límite inferior esperado; en el segundo semestre fue de 25,6% por encima del umbral. Se notificaron 45 568 fallecidos por COVID-19 mediante el SNVS. DISCUSIÓN: Los valores de mortalidad concuerdan con la evolución de la pandemia en el país. El sistema de notificación de fallecidos por COVID-19 es robusto debido al aporte de una amplia red y al cotejo con otras fuentes oficiales para completar la información en el SNVS