Thread by @miamalan

[Thread] JUST IN:

How sick did #COVID19 patients in SA get during Gauteng's #Omicron wave?

NEW @TheLancet preprint: bit.ly/3FJj6mA (via Waasila Jasat, @ProfAbdoolKarim et al.)

2. Why did study authors look @ Gauteng + not the entire SA?
1. SA's #Omicron outbreak started in Gauteng, so there's data 4 a longer period than other provinces
2. They looked @ the 1st 4 weeks of #Omicron + compared it to the same periods for Wave 2 (Beta), Wave 3 (#Delta)

3. From when to when were the 1 month periods of the waves?
- Wave 2 (Beta): 29 Nov-26 Dec 2020
- Wave 3 (#Delta): 2 May-29 May 2021
- Wave 4 (#Omicron): 14 Nov-11 Dec 2021

4. How many reported #COVID19 cases (so how many people tested positive) during the 1st month of each wave in Gauteng?

- Wave 2 (Beta): 41,046
- Wave 3 (#Delta): 33,423
- Wave 4 (#Omicron): 133,551

5. Which % of people who tested + for #COVID19 got admitted to hospital in the different waves?
- Wave 2 (Beta): 18.9% (7,774/41,046)
- Wave 3 (#Delta): 13.7% (4,574/33,423)
- Wave 4 (#Omicron): 4.9% (6,510/133,551)

6. Which % of #COVID19 hospital patients had severe disease?
- Wave 2 (Beta): 60.1% (4,672/7,774)
- Wave 3 (#Delta): 66.9% (3,058/4,574)
- Wave 4 (#Omicron): 28.8% (1,276/4,438) [2,072/ 6,510 patients = a not a documented hospital outcome when the study = submitted]

7. What counts for severe disease?
- Acute respiratory distress
- Oxygen supplementation
- Ventilation
- Intensive care unit admission
- Death

8. % of #COVID19 patients needing supplemental oxygen:
- Wave 2 (Beta): 39.4% (3,063/7,774)
- Wave 3 (#Delta): 48.8% (2,231/4,574)
- Wave 4 (#Omicron): 19.7% (875/4,438)

9. Median hospital stay:
- Wave 2 (Beta): 7 days
- Wave 3 (#Delta): 8 days
- Wave 4 (#Omicron): 4 days

10. % of cases (of total admissions) admitted among children + teens below 20 years:
- Wave 2 (Beta): 3.9% (306/7,774)
- Wave 3 (#Delta): 3.5% (161/4,574)
- Wave 4 (#Omicron): 17.7% (1,151/6,510)

11. % of hospitalised patients younger than 20 years with severe disease:
- Wave 2 (Beta): 22.5% (69/306)
- Wave 3 (#Delta): 23.0% (37/161)
- Wave 4 (#Omicron): 20.4% (172/844)

12. What does the data tell us?

Admitted patients in the 1st month of SA's #Omicron (4th) wave were 73% less likely to have severe disease than patients admitted during the 1st month of the Beta and #Delta waves.

13. Great explanation via @ProfAbdoolKarim:
1. #Omicron caused 4x more infections than #Delta in the 1st 4 wks of each GP wave
2. But #Omicron's hospital admission rate = +/- a quarter of #Delta's. So Omicron leads to almost the same nr of Delta admissions but in a shorter time.

14. #Omicron admissions don't strain the health system to same extent as #Delta admissions because Omicron leads to severe disease 73% less often than Delta (after adjustment).

15. NB: The study can't tell u how much of #Omicron's milder disease effect = is due to a less virulent virus, vaccination and/or past immunity (especially vaccination in those with past infection).

@ProfAbdoolKarim = likely all 3 play a role (probs in this order of importance).

16. As any combination of a less virulent virus, co-
morbidities, high immunity from prior infection(s)/vax may be contributors 2 #Omicron's milder disease, this study's results = not necessarily hold true 4 countries with diff co-morbidity profiles, prior infection/vax coverage.