Thread by @seanongwx

1/ Hot off the press - our study comparing Alpha, Beta, and #Delta VOCs, showing that #DeltaVariant infection was associated with more severe disease, higher viral load, and a longer duration of viral shedding.

@IDSAInfo #IDTwitter #COVID19 #SARSCoV2
doi.org/10.1093/cid/ci…

2/ The effect on severity was seen in both an analysis of Singapore's national-level data (increased odds of O2 requirement, ICU admission, and mortality), as well as a detailed analysis of an #NCID cohort (increased odds of both pneumonia and severe disease).

3/ Singapore benefits from an aggressive test-trace-isolate strategy with active case-finding, hence our cohort represents the entire spectrum of #COVID19 disease severity. Large healthcare resource buffer capacity also obviates confounding effects of resource limitations.

4/ Our findings of increased disease severity associated with #DeltaVariant corroborates work from Scotland (increased risk of hospitalisation) and Canada (increased risk of hospitalisation, ICU admission, mortality).

thelancet.com/journals/lance…
medrxiv.org/content/10.110… @DFisman

5/ Serial Ct values of the three VOCs compared to ancestral wild-type strain showed that #DeltaVariant was associated with significantly lower Ct values (a surrogate for higher viral load) throughout the entire illness duration, even up to day 21.

6/ Kaplan-Meier plots also show that #DeltaVariant was associated with a longer time to Ct >30 (which we used as a surrogate threshold for infectivity); median 18 days for Delta vs 13 days for wild-type.

7/ While Ct values are an imperfect surrogate for viral load, it is clear that there are significant differences in terms of viral kinetics between Delta and earlier strains; which potentially explains the massively increased transmissibility observed.

8/ Thankfully, while not the main aim of this paper, we observed that #vaccination remains protective against severe illness. Our findings provide an impetus for the rapid implementation of vaccination programs to mitigate the impact of #DeltaVariant on the pandemic.

9/ Further questions remain - what are the mechanisms for increased virulence and potential immune evasion? How can we bolster vaccination strategy to optimise effectiveness and durability of immunity? Active genomic surveillance is needed as the virus continues to evolve.