Emergence and Spread of B.1.1.7 Lineage in Primary Care and Clinical Impact in the Morbi-Mortality among Hospitalized Patients in Madrid, Spain.

In December 2020, UK authorities warned of the rapid spread of a new SARS-CoV-2 variant, belonging to the B.1.1.7 lineage, known as the Alpha variant. This variant is characterized by 17 mutations and 3 deletions. The deletion 69-70 in the spike protein can be detected by commercial platforms, allowing its real-time spread to be known. From the last days of December 2020 and over 4 months, all respiratory samples with a positive result for SARS-CoV-2 from patients treated in primary care and the emergency department were screened to detect this variant based on the strategy S gene target failure (SGTF). The first cases were detected during week 53 (2020) and reached >90% of all cases during weeks 15-16 (2021). During this period, the B.1.1.7/SGTF variant spread at a rapid and constant replacement rate of around 30-36%. The probability of intensive care unit admission was twice higher among patients infected by the B.1.1.7/SGTF variant, but there were no differences in death rate. During the peak of the third pandemic wave, this variant was not the most prevalent, and it became dominant when this wave was declining. Our results confirm that the B.1.1.7/SGTF variant displaced other SARS-CoV-2 variants in our healthcare area in 4 months. This displacement has led to an increase in the burden of disease.

Progressive and Parallel Decline of Humoral and T-Cell Immunity in Convalescent Healthcare Workers with Asymptomatic or Mild-to-Moderate Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

We investigated the duration of humoral and T-cell immune response in paired samples among 22 convalescent healthcare workers (HCWs). A median of 1.8 months after diagnosis, T-cell response was significantly lower in HCWs with early loss of antibodies (6 cases [27%]). After 5.1 months, antibody decline was observed in 77% of cases (41% seroreverted; P < .01), and 36% had lost T-cell response (75% lost response to spike protein). Persistence of immune response was observed in those who developed a greater adaptive immune response. Our data point to the initial immune response as the relevant player in coronavirus disease 2019 duration of protection.

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