April 16 | Daily COVID-19 LST Report

Transmission & Prevention

· Single-dose BNT162b2 offer significant short-term protection against SARS-CoV-2. Infectious disease experts from Cambridge University evaluated the effectiveness of a single-dose BNT162b2 vaccine in a cross-sectional analysis of SARS-CoV-2 positivity in 8819 healthcare workers (HCW) over two weeks in January 2021. They found asymptomatic infections were four times lower in vaccinated HCWs compared to non-vaccinated HCWs 12 or more days after the first vaccine dose (4/1,989 positive tests [0.2%, Wilson’s interval 0.1-0.5%] vs 26/3,252 [0.8%, Wilson’s interval 0.6-1.2%], p=0.004). Authors suggest single-dosage vaccinations of BNT162b2 do offer significant short-term protection against SARS-CoV-2 transmission.

· How will antigenic changes viral variations affect antibody-mediated immunity? Immunologists and virologists from the National Institute of Allergy and Infectious Diseases discuss the emergence of a new California variant of SARS-CoV-2 described in a JAMA article by Zhang, et al and explore its potential clinical consequences. Based on data from Zhang, et al and other studies of SARS-CoV-2 variants, the authors observe that viral variation can result in antigenic changes that alter antibody-mediated immunity, as seen in a South African strain partially to fully resistant to neutralization by some monoclonal antibodies in vitro. The authors suggest that even though current data shows that current vaccines effectively reduce overall mortality in the setting of antigenic variation, more research into viral transmissibility is needed in order to determine whether changes in vaccine composition are necessary to limit evasion of vaccine-induced immunity.

· S-gene target failures (SGTF) mutations confer higher transmissibility in the SARS-CoV-2 lineage B.1.1.7. Epidemiologists from the MRC Centre for Global Infectious Disease Analysis at Imperial College London conducted a community-based, whole genome analysis of a random sample of SARS-CoV-2 sequences collected from community-based diagnostic testing in England between October 1, 2020 and January 16, 2021. They found the new variant of concern (VOC) SARS-COV-2 lineage B.1.1.7 expanded rapidly and possessed an advantageous S-gene target failures (SGTF) mutation that appeared to confer higher transmissibility. Authors emphasize the importance of genomic surveillance and its potentially valuable insights into new VOC that may impact transmissibility and disease outcomes.

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