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Topic: Vaccines and Immunity
March 15, 2021
Effectiveness of the Pfizer-BioNTech COVID-19 Vaccine Among Residents of Two Skilled Nursing Facilities Experiencing COVID-19 Outbreaks — Connecticut, December 2020–February 2021
Partial vaccination with the Pfizer-BioNTech COVID-19 vaccine (from >14 days after dose 1 through 7 days after dose 2) was found to be to 63% effective against SARS-CoV-2 infection among residents of two skilled nursing facilities in Connecticut that experienced outbreaks from December 2020 – February 2021. Vaccine efficacy was similar (60%) when residents with…
March 12, 2021
Estimated Half-Life of SARS-CoV-2 Anti-Spike Antibodies More than Double the Half-Life of Anti-Nucleocapsid Antibodies in Healthcare Workers
Among healthcare-workers (HCWs) (n=118) who had a previous SARS-CoV-2 infection, 92% were still positive for anti-spike (S) antibodies compared to only 18% for IgG anti-nucleocapsid (N) antibodies after 7-10 months. At 1-3 months, 98% of HCWs were positive for anti-S antibodies compared to 85.6% anti-N antibodies. The mean half-life for anti-S antibodies was 19 days…
ChAdOx1 nCoV-19 (AZD1222) protects against SARS-CoV-2 B.1.351 and B.1.1.7
[Pre-print, not peer-reviewed] An investigation of the Oxford-AstraZeneca (ChAdOx1 nCoV-1; AZD1222) vaccine efficacy against SARS-CoV-2 variants of concern B.1.1.7 and B.1.351 in Syrian hamsters showed a 9.5-fold reduction of virus neutralizing antibody titer in vaccinated hamster sera against B.1.351 compared to B.1.1.7. Vaccinated hamsters challenged with B.1.1.7 or B.1.351 did not lose weight compared to…
Novavax Confirms High Levels of Efficacy Against Original and Variant COVID-19 Strains in United Kingdom and South Africa Trials
[Press release, not peer-reviewed] A Phase 3 trial of the Novavax vaccine (NVX‑CoV2373) in the UK indicated an efficacy of 96.4% against mild, moderate and severe disease caused by the original COVID-19 strain. The company also announced final results of its Phase 2b trial conducted in South Africa, with an efficacy of 55.4% among HIV-negative…
March 11, 2021
Epidemiological and Evolutionary Considerations of SARS-CoV-2 Vaccine Dosing Regimes
An immuno-epidemiological model suggests that a one-dose vaccination strategy would likely decrease short-term SARS-CoV-2 infections. Long-term outcomes, as well as likelihood of viral evolution driven by partial immunity, are mainly driven by relative immune robustness of one versus two doses. [EDITORIAL NOTE: A pre-print related to this manuscript was summarized on February 4, 2020] Saad-Roy…
Antibody Responses in Seropositive Persons after a Single Dose of SARS-CoV-2 MRNA Vaccine
After a single dose of either the Pfizer-BioNTech or Modernan vaccine, US vaccinees with prior SARS-CoV-2 infection (n=43) had antibody titers 10-45 times as high as those of vaccinees without prior SARS-CoV-2 infection (n=67), according to interim results of a longitudinal study. While titers of those with prior infection did not increase after the second…
Immune Response to SARS-CoV-2 Variants of Concern in Vaccinated Individuals
[Pre-print, not peer-reviewed] Sera from both individuals with prior SARS-CoV-2 infection (n=35) and individuals fully vaccinated with the Pfizer-BioNTech vaccine (n=23) showed nearly identical antibody binding responses against the B.1.1.7 Cluster 5 and CAL.20C variants compared to wild-type SARS-CoV-2. In contrast, both binding and neutralizing antibody responses among vaccinated individuals were diminished against the B.1.351…
March 10, 2021
Spike Mutations in SARS-CoV-2 Variants Confer Resistance to Antibody Neutralization
[Pre-print, not peer-reviewed] A panel of 28 SARS-CoV-2 pseudoviruses bearing single or combined spike protein mutations found in the 501Y.V1, 501Y.V2, and 501Y.V3 variants tested against a panel of monoclonal antibodies (mAbs) and convalescent patient plasma collected early in the pandemic showed that the 501Y.V2 variant was the most resistant against mAbs and convalescent plasma,…
Previous SARS-CoV-2 Infection Increases B.1.1.7 Cross-Neutralization by Vaccinated Individuals
[Pre-print, not peer-reviewed] Sera from individuals who had been previously infected with SARS-CoV-2 and received the vaccine showed equivalent neutralizing responses against the B.1.1.7 variant and original virus strain, while sera from vaccinated individuals with no prior infection showed reduced neutralization against B.1.1.7. Neutralizing activity was assessed against pseudoviruses bearing the spike protein from the…
SARS-CoV-2 501Y.V2 (B.1.351) Elicits Cross-Reactive Neutralizing Antibodies
[Pre-print, not peer-reviewed] Antibody responses to the 501Y.V2 SARS-CoV-2 variant in a cohort of patients hospitalized with COVID-19 in South Africa (n = 89) were found to be robust and showed high levels of cross-reactivity against the virus strain from the first wave. Furthermore, sera from patients infected with 501Y.V2 also neutralized the 501Y.V3 (P.1)…
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