How "toxic" is Omikejong? JAMA publishes the characteristics of the condition of thousands of infected people in endemic areas

▎ WuXi AppTec content team editor

Since the first detection of Omicron in South Africa on November 9, more than 100 countries and territories around the world have detected this variant of the new crown virus.

The degree of threat posed by Omicron depends on the characteristics of Omicron's transmissibility, immune escape ability, pathogenicity, etc., as well as our dynamic prevention and control measures. According to the latest statement released by the World Health Organization (WHO) at the end of December:

There is currently consistent evidence that Omicron spreads significantly faster than the Delta variant.

Some preliminary research data suggest that Omicron may have immune escape from vaccination or previous infections.

Data on the clinical severity of people infected with Omicron are accumulating, but remain limited.

Recently, the Journal of the American Medical Association (JAMA) published a major study reviewing the characteristics of hospitalized patients during the peak period of Omicron infection in South Africa and comparing it with the peak period of early infection. Local surveillance data in South Africa show that Omicron accounted for 81% and 95% of the test samples in November and December, respectively, and patient data in this context are of great reference significance.

The results showed that during the Omicron variant epidemic, the proportion of hospitalizations was lower for positive patients and the severity of admissions was lower, including the need for oxygen, mechanical ventilation, admission to intensive care units (ICUs), as well as lower mortality and length of hospital stay. In addition, more young patients (nearly 2/3 are unvaccinated).

Screenshot source: JAMA

Previously, South Africa experienced a total of three waves of COVID-19 peaks. Since 15 November, with the advent of Omicron, the number of local COVID-19 cases in South Africa has increased again, and by 7 December the community positivity rate has reached 26%, forming the fourth wave peak in the local area.

The study, which was sourced from South Africa's Netcare Healthcare Group, which covers 49 acute care hospitals (> 10,000 beds), assessed the characteristics of COVID-19-positive inpatients in the healthcare system during the fourth wave of the pandemic (November 15-December 7, 2021, follow-up to 20 December 2021) and compared the community-positive rates of 26% of the first three waves.

Compare the first 3 waves of outbreaks (community positivity period of 26%):

Wave 1: June 14 - July 6, 2020 (prototoxic strain)

Wave 2: December 1-23, 2020 (Beta variant)

Wave 3: June 1-23, 2021 (Delta variant)

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Specifically, the data shows that during the peak of the four waves of different outbreaks, the number of patients who have detected positive in the emergency department of the netcare system has been different, but among the patients who are positive for the new crown in the emergency department, the proportion of hospitalizations in the first three waves of the epidemic peak is generally 68%-69%, while this number has dropped to 41.3% in the peak of the fourth wave.

In terms of patient characteristics, patients hospitalized during the peak of wave 4 were significantly younger (median age 36 years, median age of 53-59 years in the first 3 waves), higher proportions of women (60.7% vs 46.3%-51.8%), and lower proportions of comorbidities (22.3% vs 52.5%-58.4%). Of the 971 patients admitted during the peak of wave 4, 24.2 percent were vaccinated, 66.4 percent were unvaccinated, and 9.4 percent were vaccinated in an unknown status.

The 971 patients admitted to hospital during the peak of wave 4 were also less ill:

Less acute respiratory illness on admission (31.6% vs 72.6% to 91.2%),

Significant decrease in the proportion of patients requiring oxygen therapy (17.6% vs 74%-82%),

The proportion of patients requiring mechanical ventilation decreased significantly (1.6% vs 8.0% to 16.4%),

Lower ICU occupancy rates (18.5% vs 29.9%-42%),

Lower mortality (2.7% vs 19.7%-29.1%),

The average length of stay was shorter (2.7 vs 19.7-29.1 days).

Outcomes of patients admitted to hospital with positive COVID-19 outcomes during the peak of 4 waves of different outbreaks (table source: reference [1])

The paper concludes that the characteristics and outcomes of HOSPITALIZED PATIENTS observed in the early stages of the 4th wave were different compared to the peak of previous waves in South Africa.

The paper also said that the results of the study have certain limitations. For example, specific data on viral genotyping in patients are lacking. As of 20 December, 7% of patients were still hospitalized. Global measures are different during the peak of each wave, and the behaviour and characteristics of patients may also vary. In addition, during disease analysis, it is difficult to completely distinguish between patients admitted to the hospital for COVID-19 or other diseases but who have tested positive.

The authors also stress that considering that as of December 2021, 44.3% of South African adults have been vaccinated, > 50% of the population has been exposed to the new crown virus, more data are needed to analyze whether the reduced risk of hospitalization of positive patients at the peak of the fourth wave of the epidemic is due to previous infections or immunity from vaccination, or whether Omicron itself is less "toxic".

This peer-reviewed study has brought us an important reference for understanding the characteristics of the disease of People infected with Omicron, but given that this is only early data, coupled with the spread of Omicron and immune escape, we still cannot underestimate the threat of Omicron, and we also expect more scientific evidence to provide more scientific reference for prevention and control.