(1) Dr. Wafaa El-Sadr presented an update on the COVID-19 pandemic globally, in the US, and NYC, focusing on the emergence and characteristics of the Omicron variant. (2) Key findings showed that Omicron is highly transmissible but may cause milder illness than Delta. (3) Vaccine effectiveness against infection declines more quickly with Omicron but boosters help improve protection, especially against hospitalization. (4) Omicron's high transmissibility combined with milder disease and vaccine protection could lead to COVID-19 becoming an endemic disease.

1. Wafaa El-Sadr, MD, MPH, MPA
COVID-19 Update
January 18th, 2022

2. Outline of Presentation
• Status of the pandemic (globally, US, and NYC)
• Update on Omicron:
• Epidemiology
• Disease severity
• Vaccine & booster effectiveness
• Convalescence and boosting
• Conclusions

3. Status of the Pandemic

4. COVID-19 Global Snapshot
As of January 18th:
• 331,306,590 confirmed cases
• 5,548,085 reported deaths
• 9,674,494,178 vaccine doses
administered
By WHO Region:
New cases in last 7 days:
• 47% in Europe
• 40% in the Americas
• 5% in the Western Pacific
• 5% in South-East Asia
• 2% in Africa
• 1% in the Eastern Mediterranean Our World in Data, John Hopkins University, WHO
Top five for 28-day cases:
United States, France, United Kingdom, Italy, Spain

5. COVID-19 in the US
New York Times

6. Daily COVID-19 Cases—NYC
NYC DOHMH

7. Community Transmission Levels
NYC DOHMH

8. Daily Hospitalizations—NYC
NYC DOHMH

9. Daily Hospitalization by Vaccination Status—NY State
NYS DOH

10. SARS-CoV-2 Variants

11. Countries With Reported Cases of the Omicron Variant
New York Times

12. SARS-CoV-2 Variant Proportions
(US)
CDC
Omicron
99.8%

13. Omicron and Transmissibility

14. Incubation Period of Omicron
• A CDC investigation of 6 individuals in one household infected with Omicron
after index case returned from international travel in late November, 2021
• Of the 6 individuals infected:
• 1 individual experienced reinfection after being fully vaccinated
• 4 individuals experienced reinfection
• 1 experienced their first infection
• Observations from the investigation suggest:
• A shorter incubation period (median period of 3 days observed in the cluster)
• A clinical syndrome similar to or milder than that associated with previously
described variants in persons who have been vaccinated or previously infected
• Increased potential for reinfection
Jansen et al., CDC MMWR (28 Dec 2021)

15. Transmission of Omicron vs. Transmission of Delta
(Household and Non-Household) (Data from the UK)
Examined >100,000 individuals who had tested positive for Omicron in the UK to see if a member of
their household tested positive within 2 weeks.
• Household transmission risk is higher for Omicron than for Delta (18% of Omicron cases
individuals gave rise to a second case vs 10% of Delta cases)
Using contact tracing data, they also estimated the number of close contacts who tested positive
following exposure and found:
• The secondary attack rate (i.e., the probability of transmitting the virus to susceptible people)
was also higher for Omicron than for Delta (15.8% for Omicron vs 10.3% for Delta for household
contacts and 8.7% for Omicron vs 3.0% for Delta for nonhousehold contacts)
SARS-CoV-2 variants of concern and variants under investigation in England (17 Dec 2021)

16. Omicron and Severity of Disease

17. Clinical Outcomes Among Individuals Infected with Omicron (California)
• Examined 52,297 cases with
SGTF (Omicron) and 16,982
cases with non-SGTF (Delta)
infections
• Omicron variant infections
were associated with
substantially reduced risk of
severe clinical endpoints and
shorter durations of hospital
stay
Times to severe outcomes among cases with Delta and Omicron infections
first detected in outpatient settings
(Delta)
(Omicron)
Lewnard et al., medRxiv pre-print (12 Jan 2022)

18. Vaccine Effectiveness

19. • Vaccine effectiveness of two doses of the
Pfizer-BioNTech vaccine against COVID-19
hospitalization caused by Omicron
• Compared effectiveness during Omicron’s
dominance in the Gauteng province vs.
period when Delta was denominate
• During the proxy omicron period, the
vaccine remained effective, but decreased
to 70%
Pfizer-BioNTech Effectiveness Against
Omicron (South Africa)
Collie et al., NEJM (29 Dec 2021)

20. Booster Effectiveness Against Infection
• Cohort study of 1,928 health care
workers in Israel who were
previously vaccinated with 2 does of
Pfizer-BioNTech
• Of the 1828, 1650 participants
(85.6%) received a Pfizer-BioNTech
booster dose
• Over the course of 39 days, infection
occurred in 44 participants including:
• 5 in boosted participants
vs.
 39 in non-boosted participants
Spitzer et al., JAMA (10 Jan 2022)

21. Booster Effectiveness Against
Infection (Omicron & Delta
Variants) (California, USA)
• Test negative control analysis including 6,657 cases
(44% delta, 56% omicron) conducted to evaluated
vaccine effectiveness (VE)
• VE following two doses of Moderna against Omicron:
• 14-90 days after: 30.4% (followed by quick decline)
• VE following Moderna booster dose:
• Against Delta infection: 95.2%
• Against Omicron infection: 62.5% (particularly low
among immunocompromised individuals)
• No 3-dose recipients were hospitalized for COVID-19
Tseng et al., medRxiv pre-print (8 Jan 2022)

22. Johnson & Johnson Effectiveness Against Hospitalization During
Omicron Wave (South Africa)
• Estimation of vaccine effectiveness (VE) of the Johnson & Johnson booster against COVID-
19 hospital admission for Omicron in >65,000 health care workers as compared to
unvaccinated individuals
• After adjusting for confounders, VE for hospitalization increased over time after the
booster dose:
0-13 days: 63% 14-27 days: 84% 1-2 months: 85%
Time since booster
Gray et al., medRxiv pre-print (29 Dec 2021)

23. Antibody Responses among Convalescent vs Convalescent/Vaccinated Persons
Serum from convalescent individuals decreased effectiveness against Omicron variant
Better effectiveness if convalescent-vaccinated or vaccinated-convalescent

24. The Way Forward

25. Omicron Case Trends in Southern Africa
Our World
in Data
South
Africa Zimbabwe
Zambia
Mozambique

26. Transition from Pandemic to Endemic

27. Conclusions
• Omicron has resulted in large surge in COVID-19 cases globally with hotspots
currently in Europe and in the Americas
• Findings indicate that Omicron is more transmissible than previous variants,
but more likely to cause asymptomatic or less severe illness
• Vaccine effectiveness following two doses is lower for Omicron compared to
the Delta variant, but booster doses has been found to improve clinical
protection and antibody response
• Omicron variant due to its high transmissibility, overall milder resulted
clinical features, and effectiveness of vaccines/boosters might pave the way
for reaching new state of equilibrium with COVID-19 pandemic