The Lambda Variant in Argentina: Analyzing the Evolution and Spread of SARS-CoV-2 Lineage C.37.

The second wave of COVID-19 occurred in South America in early 2021 and was mainly driven by Gamma and Lambda variants. In this study, we aimed to describe the emergence and local genomic diversity of the SARS-CoV-2 Lambda variant in Argentina, from its initial entry into the country until its detection ceased. Molecular surveillance was conducted on 9356 samples from Argentina between October 2020 and April 2022, and sequencing, phylogenetic, and phylogeographic analyses were performed. Our findings revealed that the Lambda variant was first detected in Argentina in January 2021 and steadily increased in frequency until it peaked in April 2021, with continued detection throughout the year. Phylodynamic analyses showed that at least 18 introductions of the Lambda variant into the country occurred, with nine of them having evidence of onward local transmission. The spatial--temporal reconstruction showed that Argentine clades were associated with Lambda sequences from Latin America and suggested an initial diversification in the Metropolitan Area of Buenos Aires before spreading to other regions in Argentina. Genetic analyses of genome sequences allowed us to describe the mutational patterns of the Argentine Lambda sequences and detect the emergence of rare mutations in an immunocompromised patient. Our study highlights the importance of genomic surveillance in identifying the introduction and geographical distribution of the SARS-CoV-2 Lambda variant, as well as in monitoring the emergence of mutations that could be involved in the evolutionary leaps that characterize variants of concern.

Immunogenicity and reactogenicity of heterologous immunization against SARS CoV-2 using Sputnik V, ChAdOx1-S, BBIBP-CorV, Ad5-nCoV, and mRNA-1273.

Heterologous vaccination against coronavirus disease 2019 (COVID-19) provides a rational strategy to rapidly increase vaccination coverage in many regions of the world. Although data regarding messenger RNA (mRNA) and ChAdOx1 vaccine combinations are available, there is limited information about the combination of these platforms with other vaccines widely used in developing countries, such as BBIBP-CorV and Sputnik V. Here, we assess the immunogenicity and reactogenicity of 15 vaccine combinations in 1,314 participants. We evaluate immunoglobulin G (IgG) anti-spike response and virus neutralizing titers and observe that a number of heterologous vaccine combinations are equivalent or superior to homologous schemes. For all cohorts in this study, the highest antibody response is induced by mRNA-1273 as the second dose. No serious adverse events are detected in any of the schedules analyzed. Our observations provide rational support for the use of different vaccine combinations to achieve wide vaccine coverage in the shortest possible time.

Longitudinal Study after Sputnik V Vaccination Shows Durable SARS-CoV-2 Neutralizing Antibodies and Reduced Viral Variant Escape to Neutralization over Time.

Recent studies have shown a temporal increase in the neutralizing antibody potency and breadth to SARS-CoV-2 variants in coronavirus disease 2019 (COVID-19) convalescent individuals. Here, we examined longitudinal antibody responses and viral neutralizing capacity to the B.1 lineage virus (Wuhan related), to variants of concern (VOC; Alpha, Beta, Gamma, and Delta), and to a local variant of interest (VOI; Lambda) in volunteers receiving the Sputnik V vaccine in Argentina. Longitudinal serum samples (N = 536) collected from 118 volunteers obtained between January and October 2021 were used. The analysis indicates that while anti-spike IgG levels significantly wane over time, the neutralizing capacity for the Wuhan-related lineages of SARS-CoV-2 and VOC is maintained within 6 months of vaccination. In addition, an improved antibody cross-neutralizing ability for circulating variants of concern (Beta and Gamma) was observed over time postvaccination. The viral variants that displayed higher escape to neutralizing antibodies with respect to the original virus (Beta and Gamma variants) were the ones showing the largest increase in susceptibility to neutralization over time after vaccination. Our observations indicate that serum neutralizing antibodies are maintained for at least 6 months and show a reduction of VOC escape to neutralizing antibodies over time after vaccination. IMPORTANCE Vaccines have been produced in record time for SARS-CoV-2, offering the possibility of halting the global pandemic. However, inequalities in vaccine accessibility in different regions of the world create a need to increase international cooperation. Sputnik V is a recombinant adenovirus-based vaccine that has been widely used in Argentina and other developing countries, but limited information is available about its elicited immune responses. Here, we examined longitudinal antibody levels and viral neutralizing capacity elicited by Sputnik V vaccination. Using a cohort of 118 volunteers, we found that while anti-spike antibodies wane over time, the neutralizing capacity to viral variants of concern and local variants of interest is maintained within 4 months of vaccination. In addition, we observed an increased cross-neutralization activity over time for the Beta and Gamma variants. This study provides valuable information about the immune response generated by a vaccine platform used in many parts of the world.

Detección de SARS-CoV-2 en contactos estrechos asintomáticos de casos confirmados por diagnóstico molecular, provincia de Buenos Aires, Argentina / Detection of SARS-CoV-2 in asymptomatic close contacts of cases confirmed by molecular diagnosis, Buenos Aires province, Argentina

Resumen La detección de SARS-CoV-2 y su implicancia en el diagnóstico de COVID-19 han sido muy debatidas en la pandemia. El objetivo de este estudio fue evaluar el costo/beneficio de la detección de SARS-CoV-2 en contactos estrechos asintomáticos (CE) mediante el uso de distintas pruebas de diagnóstico molecular. Se estudiaron 51 CE de personas con diagnóstico de SARS-CoV-2 confirmado por RTqPCR, clasificadas por el umbral de ciclos (Ct) (<20, entre 20 y 30 y >30) en hospitales públicos de la provincia de Buenos Aires. Del total de contactos estudiados el 15,7% resultó confirmado para SARS-CoV-2; no hubo contactos positivos de casos con Ct>30. La cantidad de contactos positivos de casos con Ct<20 fue significativamente mayor que la de casos con Ct>20. Las muestras con Ct<20 se asociaron a una carga viral estimada de entre uno a cuatro órdenes de magnitud de diferencia con los rangos de Ct>20. Un 13,7% de contactos positivos fueron casos con Ct<20. De las muestras positivas confirmadas por PCR, correspondientes a la semana epidemiológica 1 de 2021 (SE1), sólo un 19,35% correspondían a muestras con Ct<20 y un 50,7% con Ct entre 20 y 30. Estos datos muestran un incremento de sólo un 3,7% de casos detectados. El esfuerzo por parte del sistema de salud pública para esta estrategia, con bajo poder predictivo, puede tener un efecto negativo para el cumplimiento del aislamiento de los contactos y podría generar una demora en los resultados de los casos sospechosos, sin aportar significativamente en el control de la pandemia.

Abstract The detection of SARS-CoV-2 and its implication in the diagnosis of COVID-19 have been highly debated in the pandemic. The objective of this study was to evaluate the cost/benefit of detecting SARS-CoV-2 in asymptomatic close contacts (CC) using different molecular diagnostic tests. A total of 51 CC of people with a diagnosis of SARS-CoV-2 confirmed by RTqPCR, classified by the cycle threshold (Ct) (<20, between 20 and 30 and >30), were studied in public hospitals in the Province of Buenos Aires. Of the total contacts studied, 15.7% were confirmed for SARS-CoV-2; there were no positive contacts of cases with Ct>30 positive. The number of positive contacts of cases with Ct<20 was significantly higher than that of cases with Ct>20. Samples with Ct<20 were associated with an estimated viral load of one to four orders of magnitude difference with Ct ranges >20. A total of 13.7% of positive close contacts were from cases with Ct<20. When studying positive samples with confirmed diagnosis by PCR, corresponding to 1 epidemiological week of 2021 (EW1), only 19.35% corresponded to samples with Ct<20 and 50.7% with Ct between 20 and 30. From these data it is shown that with the CC test only 3.7% of the cases were detected. The effort by the public health system for this strategy, with low predictive power, may have a negative effect on the fulfillment of the isolation of contacts and could generate a delay in the results of suspected cases, without contributing significantly to controlling the pandemic.

Resumo A detecção do SARS-CoV-2 e seu envolvimento no diagnóstico da COVID-19 têm sido muito discutidos durante a pandemia. O objetivo desse estudo foi avaliar a relação custo/benefício na detecção de SARSCoV- 2 em casos de contatos próximos assintomático (CP), por meio do uso de diferentes testes de diagnóstico molecular. Foram estudados 51 casos de CP de pessoas com diagnóstico de SARS-CoV-2 confirmado pelo RTqPCR, sendo classificados pelo limiar de ciclos (Ct) (<20, entre 20 e 30 e >30), em hospitais públicos da província de Buenos Aires. Do total de contatos estudados, 15,7% foram confirmados para SARS-CoV-2, não houve contatos positivos de casos com Ct>30. O número de contatos positivos de casos com Ct<20, foi significativamente maior que os casos com Ct>20. As amostras com Ct<20 foram associadas a uma carga viral estimada de uma a quatro ordens de magnitude de diferença com os intervalos de Ct>20. Dos casos positivos, 13,7% foram com Ct<20. Das amostras positivas confirmadas por PCR, correspondentes à semana epidemiológica 1 de 2021 (SE1), apenas 19,35% correspondiam a amostras com Ct>20 e 50,7% com Ct entre 20 e 30. Esses dados mostram incremento de apenas 3,7% de casos detectados. O esforço por parte do sistema de saúde pública para essa estratégia, com baixo poder preditivo, pode ter um efeito negativo no cumprimento do isolamento dos contatos e poderia gerar uma demora nos resultados dos casos suspeitos, sem contribuir significativamente para o controle da pandemia.

Sputnik V vaccine elicits seroconversion and neutralizing capacity to SARS-CoV-2 after a single dose.

Massive vaccination offers great promise for halting the global COVID-19 pandemic. However, the limited supply and uneven vaccine distribution create an urgent need to optimize vaccination strategies. We evaluate SARS-CoV-2-specific antibody responses after Sputnik V vaccination of healthcare workers in Argentina, measuring IgG anti-spike titers and neutralizing capacity after one and two doses in a cohort of naive or previously infected volunteers. By 21 days after receiving the first dose of the vaccine, 94% of naive participants develop spike-specific IgG antibodies. A single Sputnik V dose elicits higher antibody levels and virus-neutralizing capacity in previously infected individuals than in naive ones receiving the full two-dose schedule. The high seroconversion rate after a single dose in naive participants suggests a benefit of delaying administration of the second dose to increase the number of people vaccinated. The data presented provide information for guiding public health decisions in light of the current global health emergency.

DETECTION OF SARS-CoV-2 IN ASYMPTOMATIC CLOSE CONTACTS OF CASES CONFIRMED BY MOLECULAR DIAGNOSIS, BUENOS AIRES PROVINCE, ARGENTINA / DETECCIÓN DE SARS-CoV-2 EN CONTACTOS ESTRECHOS ASINTOMÁTICOS DE CASOS CONFIRMADOS POR DIAGNÓSTICO MOLECULAR, PROVINCIA DE BUENOS AIRES, ARGENTINA / DETECÇÃO DE SARS-CoV-2 EM CONTATOS ESTREITOS ASSIMTOMÁTICOS DE CASOS CONFIRMADOS POR DIAGNÓSTICO MOLECULAR, PROVÍNCIA DE BUENOS AIRES, ARGENTINA

The detection of SARS-CoV-2 and its implication in the diagnosis of COVID-19 have been highly debated in the pandemic. Access to molecular diagnosis and its target population was essential in the public policy. The objective of this study was to evaluate the cost / benefit of detecting SARS-CoV-2 in asymptomatic close contacts using different molecular diagnostic tests. 51 close contacts of people with a diagnosis of SARS-CoV-2 confirmed by RTqPCR, classified by Ct (<20, between 20 and 30 and> 30), were studied in public hospitals in Province of Buenos Aires. Of all contacts studied, 15.7% were confirmed for SARS-CoV-2, there were no contacts of cases with Ct> 30 positive. The number of positive contacts of cases with Ct <20 was significantly higher than that of cases with Cts> 20. Samples with Cts <20 were associated with an estimated viral load of 1 to 4 orders of magnitude difference with Ct ranges> 20. 13.7% of positive close contacts were from cases with Ct <20. When studying positive samples with confirmed diagnosis by PCR, corresponding to EW1 of 2021, only 19.35% corresponded to samples with Cts <20 and 50.7% with Cts between 20 and 30. From these data it is shown that with the close contact test we could detect only 3.7% of cases. The effort by the public health system for this strategy, with low predictive power, may have a negative effect on the fulfillment of the isolation of contacts and could generate a delay in the results of suspected cases, without contributing significantly to controlling the pandemic.

La detección de SARS-CoV-2 y su implicancia en el diagnóstico de COVID-19 han sido muy debatidos en la pandemia. El acceso al diagnóstico molecular y su población destinataria fue parte esencial de las políticas públicas. El objetivo de este estudio fue evaluar el costo/beneficio de la detección de SARS-CoV-2 en contactos estrechos asintomáticos mediante el uso de distintas pruebas de diagnóstico molecular. Se estudiaron 51 contactos estrechos de personas con diagnóstico de SARS-CoV-2 confirmado por RTqPCR, clasificadas por Ct (<20, entre 20 y 30 y >30) en hospitales públicos de la Provincia de Buenos Aires. Del total de contactos estudiados el 15,7% resultó confirmado para SARS-CoV-2, no hubo contactos de casos con Ct>30 positivos. La cantidad de contactos positivos de casos con Ct<20 fue significativamente mayor que la de casos con Cts>20. Las muestras con Cts<20 se asociaron a una carga viral estimada de entre 1 a 4 órdenes de magnitud de diferencia con los rangos de Ct >20. Un 13,7% de contactos estrechos positivos fueron de casos con Ct<20. Al estudiar muestras positivas con diagnóstico confirmado por PCR, correspondientes a la SE1 del 2021, sólo un 19,35% correspondían a muestras con Cts<20 y un 50,7% con Cts entre 20 y 30. A partir de estos datos se muestra que con el testeo de contactos estrechos podríamos detectar sólo un 3,7% de casos. El esfuerzo por parte del sistema de salud pública para esta estrategia, con bajo poder predictivo, puede tener un efecto negativo para el cumplimiento del aislamiento de los contactos y podría generar una demora en los resultados de los casos sospechosos, sin aportar significativamente a controlar la pandemia.

A detecção de SARS-CoV-2 e sua implicação no diagnóstico de COVID-19 têm sido altamente debatidos na pandemia. O acesso ao diagnóstico molecular e à sua população-alvo era parte essencial das políticas públicas. O objetivo deste estudo foi avaliar o custo / benefício da detecção da SARS-CoV-2 em contatos próximos assintomáticos usando diferentes testes de diagnóstico molecular. 51 contatos próximos de pessoas com diagnóstico de SARS-CoV-2 confirmado pelo RTqPCR, classificados pelo Ct (<20, entre 20 e 30 e> 30), foram estudados em hospitais públicos da Província de Buenos Aires. Do total de contatos estudados, 15,7% foram confirmados para SARS-CoV-2, não houve contato de casos com Ct> 30 positivo. O número de contatos positivos de casos com Ct <20 foi significativamente maior que o de casos com Ct> 20. As amostras com Cts <20 foram associadas a uma carga viral estimada de 1 a 4 ordens de diferença de magnitude com intervalos de Ct> 20. 13,7% dos contatos próximos positivos eram de casos com Ct <20. Ao estudar amostras positivas com diagnóstico confirmado por PCR, correspondentes a EW1 de 2021, apenas 19,35% corresponderam a amostras com Cts <20 e 50,7% com Cts entre 20 e 30. A partir desses dados, mostra-se que com o teste de contato próximo poderíamos detectar apenas 3,7% dos casos. O esforço do sistema público de saúde por essa estratégia, com baixo poder preditivo, pode repercutir negativamente no cumprimento do isolamento dos contatos e pode gerar atraso nos resultados dos casos suspeitos, sem contribuir significativamente para o controle da pandemia.

Persistence of antibodies IgG to SARS-CoV2 in health care workers ­ Province of Buenos Aires / Persistencia de anticuerpos IgG contra SARS-CoV2 en personal de salud - provincia de Buenos Aires.

Aim: To evaluate the persistence of IgG antibodies to SARS-CoV2, in health workers of the public subsector of the Province of Buenos Aires, and correlate it with demographic variables (sex, age) and other health indicators (diagnosis of COVID-19, comorbidities and pregnancy). Methodology: Descriptive, observational, cross-sectional study. Health workers with a positive result in a first sample (N = 388) underwent a second test to evaluate the persistence of antibodies by ELISA. Results: Of the 386 people evaluated with a conclusive result, 296 had a first positive result between 30 and 90 days before the second test, of these, 90% had detectable antibodies. In those with a positive result more than 90 days ago (45), a significant decrease in persistence of 26.7% was observed. There were no significant associations between demographic and health variables and the second test result. Conclusion: Antibodies remain detectable for at least 90 days in 90% of the cases analyzed. It is main to continue this study over time to have a major period of time between tests. The information shown here throws interesting and promising data regarding the possible protection of new COVID-19 infections in personnel with high risk exposure. This evidence could contribute to decision-making, both at the local and regional level, for the adequate vaccination planning, as well as for the management in the event of a possible second wave scenario of COVID-19 pandemic in Latin America.

Objetivo: evaluar la persistencia de los anticuerpos IgG contra SARS-CoV2, en trabajadores de salud del subsector público de la Provincia de Buenos Aires, y correlacionarla con variables demográficas (sexo, edad) y otros indicadores de salud (diagnóstico de COVID-19, comorbilidades y embarazo). Metodología: Estudio descriptivo, observacional, de corte transversal. Al personal de salud con un resultado positivo en una primera muestra (N=388) se les realizó una segunda prueba para evaluar la persistencia de anticuerpos mediante ELISA. Resultados: De las 386 personas evaluadas con resultado concluyente, 296 contaban con un primer resultado positivo entre los 30 y los 90 días anteriores a la segunda prueba, el 90% presentó anticuerpos detectables. En aquellas personas con un resultado positivo hacía más de 90 días (45) se observó una caída significativa en la persistencia del 26,7%. No hubo asociaciones significativas entre las variables demográficas y de salud y el resultado de la segunda prueba. Conclusión: Los anticuerpos se mantienen detectables por al menos 90 días en el 90% de los casos analizados. Resulta fundamental continuar este estudio en el tiempo para contar con un período de tiempo mayor entre pruebas. La información aquí mostrada arroja datos interesantes y prometedores en cuanto a la posible protección de nuevos contagios de COVID-19 en personal con alta exposición de riesgo. Estas evidencias podrían contribuir a la toma de decisiones, tanto a nivel local como regional, para la adecuada planificación de la vacunación, así como también, para el manejo de la pandemia ante una posible segunda ola de casos en América Latina.