Thread by @vipintukur

Natural immunity post-#SARS2 infection may not be perfect agains #Delta variant!!

A new study from #Australia:

“The duration & magnitude of #SARS2 immunity after infection, especially wrt the emergence of new VOCs”

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At 12 months after mild-COVID19:

1->90% of convalescents remained seropositive for RBD-IgG & 88.9% had circulating RBD-specific memory B cells.

2-Despite this, only 51.2% convalescents had serum neutralising activity against homologous live-SARS2 virus

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3-The neutralising activity decreased to 44.2% against live Alpha, 4.6% against Beta, 11.6% against Gamma & 16.2%, against Delta

4-Spike & non-Spike-specific T cells were detected in >50% of convalescents

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5- T cells frequency values were higher for S antigen compared to non-S antigens

6-Despite high prevalence & maintenance of S-specific T cells in convalescents at 12 mo, T cell functionality after stimulation with Sepitopes corresponding to VoC was severely affected

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Interpretation:

1-SARS2 immunity is retained in a significant proportion of mild #COVID19 convalescents 12 mo post-infection in the absence of re-exposure to the virus

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2-Despite this, changes in the amino acid sequence of Spike antigen that are present in current VoC result in virus evasion of neutralising antibodies, as well as evasion of functional T cell responses

3-Natural immunity may not protect you against new VOC including Delta

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4-A new wave can be started by the existing Delta variant still circulating here

5-One needs to avoid complacency! You don’t need a need a new variant to ignite a new surge in cases

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medrxiv.org/content/10.110…