(1/5) Perhaps 20-50% of people already have T cells which recognise the virus causing #COVID19. This study shows that these T cells result from past infections with the coronaviruses which can cause the common cold. Are lots of people already immune? Hold on! It's not so simple.
(2/5) If past infection with other coronaviruses really did provide immunity, we wouldn't see super-spreading events like this one, where 87% of people were infected.
(3/5) We also wouldn't see family clusters like these.
(4/5) At best, these cross-reactive T cells which have been discovered might provide partial immunity. That is, they might reduce the severity of illness. But this is highly speculative and requires further research.
(5/5) There's no evidence to suggest that a vast proportion of the population is already immune to #SARSCoV2, and no evidence to suggest that herd immunity is now suddenly within reach. We still need a vaccine to beat this virus.
