New study of 200 #COVID19 patients, many with mild or no symptoms, suggests that up to TWICE as many people than detected by antibody tests may be immune, based on tests for T-cell immunity (cells that kill virus-infected cells). 1/

@thespybrief https://news.ki.se/immunity-to-covid-19-is-probably-higher-than-tests-have-shown?_ga=2.140767861.677108381.1593454468-436267287.1454932504

This study included hospitalized & non-hospitalized patients and exposed *asymptomatic* family members who returned to #Sweden after holidaying in the Alps in March. Healthy ASYMPTOMATIC blood donors who donated in 2020 and 2019 (pre- #pandemic control group) were also included.

WOW. ~30% of blood donors in May 2020 had #COVID19-specific T cells, *much higher* than previous antibody tests showed (7% in this study).

Not only did patients with confirmed #COVID19 have T-cell immunity, so did many of their exposed *asymptomatic* family members.

Encouraging news. Patients with severe #COVID19 often developed a *strong* T-cell response AND antibodies. In patients with mild symptoms, it was not always possible to detect antibodies, but many still showed a *marked T-cell response* (likely meaning that they are also IMMUNE).

These T-cell results are consistent with studies after vaccination with approved vaccines for other viruses.

Larger/longer-term studies are needed on T cells & antibodies to understand how long-lasting the immunity is, and how these 2 types of #COVID19 immunity are related.

Important: these are PRELIMINARY data that have not yet been peer-reviewed. Link to the pre-print, published online is provided below.

100% of severe convalescent (recovered) #COVID19 patients had antibodies vs 64% of exposed relatives (bottom row).

https://www.biorxiv.org/content/10.1101/2020.06.29.174888v1.full.pdf

Overall, this study is encouraging, as it suggests that more people may be immune to #coronavirus than previously shown by antibody testing.

T-cell immunity could last longer than antibodies (more study needed). If so, that's great news for herd immunity. https://twitter.com/DrDenaGrayson/status/1278106706120183813?s=20