May 10, 2021: The World Health Organization published a Scientific Brief, with the following key messages:
- Within 4 weeks following infection, 90-99% of those infected develop neutralizing antibodies
- In most people, immunity remains robust against reinfection for at least 6-8 months (that is the longest followup period so far)
- Besides targeting the spike protein, natural immunity’s cellular immunity also targets other viral proteins
- Protection is still not well understood
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July 20, 2021: Cohen et al in the journal Cell Reports: Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells
- Most recovered Covid-19 patients mount broad, durable immunity after infection
- Neutralizing antibodies show a bi-phasic decay with half-lives of more than 200 days
- Spike IgG+ memory B cells increase and persist post-infection
- Durable polyfunctional CD4 and CD8 T cells recognize distinct viral epitope regions.
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April 20, 2021: Ivanova et al, in MedRxiv: Discrete immune response signature to SARS-CoV-2 mRNA vaccination versus infection
- There was a dramatic upregulation of interferon signaling (IFN) in the patients but not in the vaccinated subjects.
- Anti-NC antibodies wre only detectec in patients, not in vaccinated subjects.
- IgG antibody levels remained high for at least 7 weeks after the first vaccine dose, but IgA antibody titers declined steadily beginning 1 week after the second vaccine dose.
- A striking expansion of circulating plasmablasts were observed in patients, but not after vaccination.
- Plasmablasts for genes involving IL-6 receptor signaling were enriched for both.
- Infection potently induced IFN responses, not observed in the vaccinated subjects.
- Cytotoxic CD4 T cells were observed in patients but were absent in vaccinated subjects.