Chen Saijuan's team's latest research: the proportion of severe cases in hospitalized patients with the new crown is about 3%, and the Spring Festival will accelerate the wave of infection, and vulnerable groups need to be protected

With the continuation of the COVID-19 epidemic in the recent autumn and winter and the adjustment of public health prevention and control measures, SARS-CoV-2 infection has spread
widely in China.

Thanks to strong non-pharmaceutical public health interventions, including large-scale nucleic acid testing, quarantine and travel restrictions, China has effectively prevented a large-scale outbreak of the new crown epidemic, and before November 2022, only a small number of people in mainland China had been infected with the new crown.

As of December 13, 2022, more than 90% of the country's population has received at least 2 doses of inactivated vaccine, and the third booster vaccination rate for people over 60 years old and over 80 years old has reached 86.
6% and 66.
4%,
respectively.
Vaccination and booster shots are effective in preventing the progression of critical illness
after infection.

At the end of 2022, China adjusted its new crown epidemic control measures, and on December 26, 2022, the National Health Commission announced that from January 8, 2023, the new crown epidemic in China will be changed from Class A managed Class B infectious diseases to Class B infectious diseases
managed by B management.

However, the rise of various Omicron subtypes has created new challenges
for public health systems.
In particular, most people in our country will experience a first infection or a breakthrough infection
in the coming period.
Although two doses of the vaccine or booster shots can effectively induce neutralizing antibodies against the new coronavirus, this humoral immunity can only be maintained for about 6 months
.
In addition, the widely vaccinated new crown vaccine in China is against the original strain of the new crown virus, and the neutralizing antibodies induced by it are difficult to prevent new Omicron subtypes
such as BA.
4, BA.
5, XBB, BQ.
1.
Therefore, when faced with the coming wave of Omicron infections, the herd immunity intensity may not be optimal
.

Recently, Chen Saijuan, Liu Feng, Wang Shengyue, Meng Guoyu, Fan Xiaohong of Shanghai Public Health Clinical Center and others from Ruijin Hospital affiliated to Shanghai Jiao Tong University School of Medicine published a title entitled: Primary assessment of the diversity of Omicron sublineages and the epidemiologic features of autumn/ Winter 2022 COVID-19 wave in Chinese mainland research paper
.

Public data from August 31, 2022 to November 29, 2022 show that the overall prevalence of severe/critical cases nationwide is 0.
035%, while the analysis of 5706 symptomatic patients admitted to Shanghai Public Health Clinical Center from September 1, 2022 to December 26, 2022 shows that 2.
68% (153 cases) have comorbidities, and 0.
35% (20 cases) have severe/critical cases without comorbidities
。

These observations remind the health care sector to devote more resources
to severe/critical cases.
In addition, mathematical prediction models show that the autumn and winter outbreak may sweep through major Chinese cities by the end of the year, while some central and western provinces and rural areas will experience an infection wave in mid-to-late January 2023, and the large movement of people during the Spring Festival (January 21, 2023) may greatly increase the duration and intensity
of the upcoming outbreak.

Taken together, these preliminary data highlight the need to allocate resources for early diagnosis and effective treatment of severe/critical cases, as well as for the protection of vulnerable groups, especially in rural areas, in order to ensure a smooth exit from the pandemic and socio-economic recovery
.

In this study, the research team randomly selected 378 COVID-19 patients detected by the Shanghai Public Health Clinical Center between November 16 and December 12, 2022, and sequenced
them using whole genome targeted sequencing technology.
These patients all developed symptoms common to patients with mild/moderate COVID-19, such as fever, headache, and cough, and none had developed severe symptoms
at the time of writing.
After rigorous quality checks, 369 samples with genome coverage of more than 80% were used for subsequent analysis
.

The sequencing results showed that among the above 369 genomes, 353 (95.
66%) genomes were concentrated in 4 Omicron lineages - BA.
5.
2 (172, 46.
61%), BA.
5.
3 (118, 31.
98%), BA.
2.
75 (36, 9.
76%), and recombinant strains (27, 7.
32%)
.

In the above four Omicron lineages, one or two subtypes account for a large proportion, for example, BF.
7 accounts for 25% in BA.
5.
2, BQ.
1 accounts for 95% in BA.
5.
3, BN.
1 accounts for 61% in BA.
2.
75, and XBB accounts for 93%
in recombinant strains.

Further retrospective showed that 94% (105/112) of BQ.
1 infections and 96% (24/25) of XBB infections came from abroad
.
Both BQ.
1 and XBB are new Omicron subtypes in Europe and North America, so they may have only recently been imported into Shanghai
.
For BA.
5.
2, including BF.
7, 38%-64% of the infected cases can be classified as imported cases, and the rest can be traced back to other parts of the mainland, indicating that BA.
5.
2 and BF.
7 may have been widely spread
in many places before they appeared in Shanghai.

The research team examined the journals of new cases in various cities and found that BF.
7 was the main source in Beijing, while BA.
5.
2 was the main in Guangzhou, and cases with contact history in Beijing were mainly infected with BF.
7, and cases with contact history in Guangzhou were mainly infected with BA.
5.
2
.

As of November 29, 2022, the total incidence of severe/critical cases among new crown infected people nationwide is 0.
035%.

Since large-scale nucleic acid testing is no longer being carried out in the near future, it is not possible to determine the actual number of infected people, especially the number of
asymptomatic infections.

To assess the proportion of severe/critical cases among symptomatic hospitalized patients, the research team carefully examined 5,706 symptomatic patients admitted to Shanghai Public Health Clinical Center between September 1 and December 26, 2022, and divided them into 4 groups
based on symptom severity and past medical history.
Among them, 5533 (96.
97%) patients were classified as mild/moderate cases, and the remaining 173 (3.
03%) patients developed severe/critical cases
.
Of the 173 severe/critical cases, 153 (2.
68%) had severe comorbidities and 20 (0.
35%) had no comorbidities
.

Of these patients, disease severity correlated significantly with age, with a median age of 66 years for severe/critical cases without comorbidities, 59 years for severe/critical cases with comorbidities, and 39 years
for mild/moderate cases.
In addition, the proportion of severe/critical illness is significantly higher in men than in women
.

Next, the research team performed mathematical modeling and used time-delay differential equations to assess the spread
of the epidemic in several major cities in China (Beijing, Shanghai, Guangzhou, Chongqing) and several central and western provinces (Gansu, Qinghai, Shaanxi, Sichuan).
Forecasts show that the wave of infections in Guangzhou has passed, Beijing, Shanghai and Chongqing urban areas are in the middle of the wave and may pass by the end of 2022, while the suburbs of Chongqing are expected to see a wave
of infections in early February 2023.

It is worth noting that with the arrival of the Spring Festival on January 21, 2023, there will be a large number of people movements in mid-January, and forecasts show that the Spring Festival will accelerate the wave of infections by 15-30 days
.
The wave of infections in the central and western provinces is expected to just begin, with Sichuan expected to peak slightly earlier than Shaanxi, Gansu and Qinghai
.

The research team analyzed Chinese mainland data on all confirmed COVID cases as of November 29, 2022, and obtained a rough cumulative incidence of severe/critical illness of 0.
035%, according to this ratio, if half of China's population (about 700 million people) were infected in a relatively narrow time window (e.
g.
, within 4-6 weeks), then these severe/critical cases would require 200,000-250,000 ICU beds
.

According to the 5706 symptomatic patients admitted to Shanghai Public Health Clinical Center from September 1 to December 26, 2022, 173 cases (3.
03%) were diagnosed as severe/critical
.
Although no deaths have been reported at press time, some patients are in critical condition and could be fatal, highlighting the urgent need
for ICU wards in places such as Shanghai, where the outbreak is ongoing.

The research team said that a large amount of research evidence suggests that advanced age, as well as several comorbidities (hypertension, cardiovascular disease, diabetes, cancer, etc.
) are major risk factors for severe/critical illness, given the current rapid spread of Omicron, elderly people in remote areas of China, especially those in poor health, are at greater risk of developing serious illness in the coming weeks or months, and moreover, some areas, especially in rural areas, lack drugs and ICU facilities
.

The research team recommends that a home reporting system based on antigen testing should be established immediately through urban and rural community medical centers/stations to collect the information of
people infected with COVID-19.
Over-the-counter medications should be given to symptomatic patients in low-risk groups (vaccinated people under 60 years of age without comorbidities) and prompt effective antiviral therapy (such as Paxlovid or VV116
) in high-risk groups (people over 60 years of age, particularly those with comorbidities or incompletely vaccinated).
In particular, it is possible to consider urgently authorizing the development of VV116
by scientists in our country.

At the same time, precise non-pharmaceutical public health measures such as wearing N95 masks, maintaining social distancing in enclosed spaces, and increasing the number of means of transportation to avoid traffic congestion should be carried out to reduce the peak of infection and relieve pressure
on the medical system.
In addition, the storage and supply of specific drugs and symptomatic drugs in rural areas should be accelerated to avoid disease exacerbation and death
due to delayed treatment.

The research team also recommends that the recently approved inhaled vaccine be used to protect people who are not infected with Omicron, and that the unapproved bivalent vaccine against the Omicron subtype BA.
4/BA.
5 be used for the fourth booster dose
of health professionals and primary workers.

Finally, excess deaths, including direct or COVID-19-related deaths, must be recorded, and the timeliness and accuracy of these data is critical for up-to-date assessments and projections of current pandemic trends to ensure evidence-based decision-making is done
correctly.