Antiviral Drugs and Vaccines for Omicron Variant: A Focused Review

Table 1

Structural and clinical characteristics of delta and Omicron variants.

Characteristics	Delta (B.1.617.2)	Omicron (B.1.1.529)	References
Number of mutations	17	30 or more	[1]
Transmissibility defined by effective (instantaneous) reproduction number	High	3.19 times greater than that of delta (95% confidence interval: 2.82–3.61)	[5]
Reinfection	Breakthrough infections seen	More common than delta but less severe illness	[6,7]
Vaccine efficacy (VE)			[6]
3 dose of VE at 14–60 days	93.7%	71.6%
3 dose of VE after 60 days	86%	47.4%
Clinical profile	Can be severe	Mild-to-moderate
(1) Incubation period	4-5 days	3 days	[7]
(2) Contagiousness	One person can infect 2-3 persons	One person can infect 6 persons	[8]
(3) Duration of illness	14 days usually	Less than 10 days usually	[9]
(4) Severity of illness	More severe	Mild-to-moderate	[10]
(5) Anosmia and dysgeusia	More common	Rare	[11]
Diagnosis by RT-PCR (NAAT) tests	Not impacted	Not impacted except for Thermo Fischer TaqPath due to deletion of position 69-70 in spike protein	[1]
Severity of cases	Very severe	40–70% less severe than delta	[12, 13]
Hospitalisation rate	Higher rate as compared to Omicron	53% reduction compared to delta	[14]
ICU admissions	Higher as compared to Omicron	74% reduction compared to delta	[14]
Need for invasive ventilation	Higher as compared to Omicron	91% reduction compared to delta	[14]
Mortality	Higher rate as compared to Omicron	Very rare, almost zero as compared to delta	[14]
Length of hospital stay	Longer duration	3.4 days shorter or 69.6% reduced as compared to delta	[14]
Therapeutics and drugs efficacy			[9–11, 15–17]
(1) Remdesivir	Effective	Effective
(2) Ritonavir-boosted nirmatrelvir	Effective	Effective
(3) Molnupiravir	Effective	Effective
(4) Sotrovimab (VIR-7831)	Effective	3-fold reduced efficacy
(5) REGEN-COV™	Effective	Not effective
(6) Bamlanivimab with etesevimab	Effective	Not Effective