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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant extensively escape neutralizing antibodies by vaccines or infection. We assessed serum neutralizing activity in sera from Delta infection after vaccination and Delta infection only against SARS-CoV-2 Wuhan-Hu-1 (WA1), Beta, Delta, and Omicron. Sera from Delta infection only could neutralize WA1 and Delta but almost completely lost capacity to neutralize Beta and Omicron. However, Delta infection after vaccination resulted in a significant increase of serum neutralizing activity against WA1, Beta, and Omicron. This study demonstrates that breakthrough infection of Delta substantially induced high potency humoral immune response against the Omicron variant and other emerged variants. [ABSTRACT FROM AUTHOR]

Background: The duration of humoral and T and cell response after the infection of SARS-CoV-2 remains unclear.Methods: We performed a cross-sectional study to assess the virus-specific antibody and memory T and B cell responses in COVID-19 patients up to 343 days after infection. Neutralizing antibodies and antibodies against the receptor-binding domain, spike, and nucleoprotein of SARS-CoV-2 were measured. Virus-specific memory T and B cell responses were analyzed.Results: We enrolled 59 COVID-19 patients, including 38 moderate, 16 mild, and five asymptomatic patients; 31 (52.5%) were men, and 28 (47.5%) were women. The median age was 41 (interquartile range [IQR]: 30-55). The median day from symptom onset to enrollment was 317 days (range 257 to 343 days). We found that approximately 90% of patients still have detectable IgG antibodies against spike and nucleocapsid proteins and neutralizing antibodies against pseudovirus, whereas ~60% of patients had detectable IgG antibodies against receptor binding domain and surrogate virus-neutralizing antibodies. SARS-CoV-2-specific IgG + memory B cell and IFN-γ secreting T cell responses were detectable in over 70% of patients.Conclusions: SARS-CoV-2-specific immune memory response persists in most patients nearly one year after infection, which provides a promising sign for prevention from reinfection and vaccination strategy. [ABSTRACT FROM AUTHOR]

Data concerning the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic and paucisymptomatic patients are lacking. We report a 3-family cluster of infections involving asymptomatic and paucisymptomatic transmission. Eight of 15 (53%) members from 3 families were confirmed with SARS-CoV-2 infection. Of 8 patients, 3 were asymptomatic and 1 was paucisymptomatic. An asymptomatic mother transmitted the virus to her son, and a paucisymptomatic father transmitted the virus to his 3-month-old daughter. SARS-CoV-2 was detected in the environment of 1 household. The complete genomes of SARS-CoV-2 from the patients were > 99.9% identical and were clustered with other SARS-CoV-2 sequences reported from China and other countries. [ABSTRACT FROM AUTHOR]