On March 29, the journal Emergeng Microbes & Infections published a review from three academics from the University of Hong Kong School of Medicine: Lessons learned from the fifth wave of COVID-19 in Hong Kong in early 2022, summarizing 6 lessons:
The dominant strain of the fifth outbreak in Hong Kong, Omicron BA.2, is the most contagious but least pathogenic of all SARS-CoV-2 strains, and its characteristics are very different from those of the early global epidemic strains.
The high mortality rate from the fifth outbreak in Hong Kong comes from a large number of elderly patients who have not been vaccinated, have not completed full vaccination, or are less effective in vaccination.
Infection with Omicron BA.2 is common in children, but there is no significant change in overall infection rate or severity.
Rapid antigen testing plays an important role in finding infected people quickly and reducing the consumption of public resources.
Hong Kong's healthcare system is under enormous pressure in the fifth round of the outbreak, but it has not collapsed and should not collapse.
Home isolation is a viable and cost-effective option that helps reduce the exposure time and risk of transmission of infected people in public places.
The full text is compiled below. (Note: This article is OA open access, due to length reasons, some of the content has been deleted)
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From 31 December 2021 to 23 March 2022, Hong Kong's fifth round of COVID-19 has claimed 6,356 lives.
On March 12, Hong Kong's COVID-19 death rate reached 3.73/100,000, the highest in the world, far exceeding the US 0.38 and Singapore 0.17. On 23 March, nucleic acid testing and rapid antigen testing showed that in the past 24 hours, there were 4246+7990 new home cases in Hong Kong, with a cumulative report of 1075519 cases, accounting for 14.5% of the total population.
Prior to the fifth outbreak, Hong Kong had managed to have no homegrown cases for nearly 100 days due to modest non-pharmacological intervention (NPI) and strict border control measures.
Hong Kong has previously had success in containing both the COVID-19 Alpha and Delta strains. In November 2021, Hong Kong reported the first human case of infection with the Omicron mutant strain, followed by a rapid determination of the full sequence of Omicron. However, the epidemic quickly entered the outbreak period and was out of control under close monitoring.
Although we had implemented several NPI measures prior to the outbreak, the effects were questionable. It is widely believed that NPI measures alone (e.g., social distancing, mass nucleic acid testing, closure of restaurants and other high-risk establishments, close contact tracing, quarantine) can prevent severe outbreaks caused by alpha or Delta strains, but these measures may not be sufficient when Omicron becomes a mainstream strain.
The fifth round of the epidemic is a turning point in Hong Kong's fight against COVID-19, and the lessons learned from it will be taken into account in other countries and regions' epidemic prevention measures, and here are 6 hard-won lessons.
01.
First, understand the difference between Omicron BA.2 in terms of transmissibility and pathogenicity.
The mainstream strains of the fifth round of the epidemic in Hong Kong are very different from the previous early global epidemic strains and pathogenic characteristics. The Omicron BA.2 mutant strain is currently the most contagious but least pathogenic of all SARS-CoV-2 strains.
In addition, Omicron BA.2 has immune escape. Currently, 91.3% of the population of Hong Kong, China, has received the first dose of the vaccine, 81.3% of the population has received the second dose, and more than one-third of the population has received the third dose of booster. Most of those infected in the fifth outbreak were breakthrough infections, and 500 of them were secondary infections for Omicron BA.2.
After breakthrough or re-infection of Omicron BA.2, antibodies rise rapidly and stabilize within 3 to 5 days after viral nucleic acids and antigens are detectable. The entire process (induction of antibody production, disease outcome, and window of viral shedding) was shortened by at least 2 days compared to people infected with the original SARS-CoV-2 strain.
More than 99.9% of Omicron BA.2 infections in Hong Kong were asymptomatic or mild, making it more difficult to identify infected people and implement zero clearance policies.
Due to the protective effect of the vaccine, the clinical manifestations of Omicron BA.2 infection are no more severe than those of the flu or the common cold. At any point in time, there are fewer than 150 severe cases and fewer than 150 cases requiring ICU treatment.
02.
Second, the high mortality rate in Hong Kong's fifth outbreak came from a large number of elderly patients who were not vaccinated, did not complete full vaccination, or were less effective in vaccination.
Image source: https://covid19.sph.hku.hk/dashboard
While only 14.5%, 7.6% and 5.4% of Hong Kong's population is 60-69 years old, 70-79 years old and over, it accounts for 13.5%, 20.9% and 51.4% of hospitalized cases, as well as 8.4%, 16.6% and 70.8% of the deaths in the fifth round of the outbreak.
In other words, 85.8% of hospitalizations and 95.8% of deaths in the fifth round of the outbreak came from the elderly population of the above three age groups, and about 90% of deaths did not complete two doses of vaccination.
As of 17 March 2022, about 90% of the population in Hong Kong has received at least one dose of the vaccine (Figure 1A). But at the start of the outbreak in February, less than 20 percent of Hong Kong's 80-year-old population was vaccinated against COVID-19, in stark contrast to more than 60 percent of seasonal influenza vaccination rates in the same group. The 70-79 age group is slightly more vaccinated, but overall it is also low.
Figure 1: COVID-19 vaccinations in Hong Kong.
A: From February 26, 2021 to March 17, 2022, the number of unvaccinated, first dose only, two doses, and booster injections was given as a percentage of the total population and age group (including Sinovac and BioNTech).
B: Percentage of First, Second, or Booster Injections given to Sinovac and BioNTech in each age group and in the general population.
In the two age groups of 70-79 years and over, 60-70% of the elderly population received the Sinovac covid-19 vaccine (Figure 1B), with mortality rates of 86.16.3 per 1 million and 14.63 per 1 million, respectively. The mortality rates in the 60-69 years, 50-59 years, and 40-49 years old age groups were 393.7, 125.2, and 33.3, respectively (Figure 2A), and the number of hospitalized or ICU patients over the age of 60 years (Figure 2B) was also higher.
Figure 2: Vaccination reduces covid-19 mortality in the fifth round.
A: Overall and age group mortality rates from December 31 to March 17, 2021.
B: Hospitalization rate by age group.
C: ICU occupancy rate by age group.
D: mortality rates for all age groups without vaccination, first dose, two doses, or booster injections.
Comparing the mortality rate of unvaccinated people over 80 years of age (145.312/1 million people) with the mortality rate of the same age group (22.111.7/1 million people) with the second or third dose of the vaccine, there was a 6.6-fold difference. For age groups aged 70-79, 60-69, and 50-59 years, the difference in mortality between unvaccinated and fully vaccinated groups was 15.1, 27.1, and 63.1 times (Figure 2D).
The benefits of vaccination were significantly greater in the relatively young group (how much of this may be attributed to age and vaccine options, with younger groups receiving more BioNTech).
There were no deaths in those with three doses of BioNTech or two doses of Sinovac plus one dose of BioNTech, i.e., boosting bioNTech reduced the risk of Omicron BA.2 infection and prevented serious illness and death. This is largely consistent with the actual data in Singapore: fortifying the mRNA vaccine resulted in a 24.8-fold reduction in mortality in the over-80 age group and a 4.1-fold reduction compared to the under-vaccination age group.
In addition, breakthrough infections were found even in a small percentage of people receiving BioNTech booster injections, mostly asymptomatic or mild. Therefore, before the next generation of Omicron variant-specific vaccines are available, intensive injections of highly effective vaccines such as BioNTech should be the best way to prevent infection, serious illness or death.
A number of urgent measures have been implemented to reduce mortality among older persons, including:
Emergency vaccinations;
Closed-loop management of nursing homes to minimize contact between the elderly and their caregivers and the outside world;
Use of Paxlovid and Molnupiravir in high-risk patients;
Regular rapid antigen testing of the elderly population in order to detect and isolate infected people as early as possible;
All elderly patients who need to be hospitalized are assigned to designated hospitals in order to receive better treatment;
Isolation of some of the high-risk elderly who are not infected.
In a way, the death of hong Kong's unvaccinated elderly population is a expected tragedy, and the precious life of Hong Kong's fifth round of the epidemic has taught the world a profound lesson: we need to protect the elderly through effective COVID-19 vaccines.
03.
Third, Omicron BA.2 infection is common in children, but the pathogenicity is not as high as observed in the fifth outbreak.
Since vaccination programmes for children have only just begun at the beginning of the current outbreak (Figure 1A), it is understandable that the number of infections in the 0-19 age group accounts for 8% of the total number of infections, and the overall infection rate of children is not higher than that of other age groups.
Although some cases of Omicron BA.2 infection in children have caused widespread concern and panic, Omicron BA.2 infection in children is not particularly serious or fatal.
A total of 9 child deaths have been reported, and the mortality rate in the 1-19 age group is 0.81/100,000, which is basically flat or even lower than that of 7 cases (0.87) in the 20-29 age group, 14 cases (1.24) in the 30-39 age group, and 35 cases (3.06) in the 40-49 age group. A similar trend can be seen when comparing mortality (Figure 2A), hospitalization rate (Figure 2B), and ICU occupancy rate (Figure 2C). In the 12- to 19-year-old age group, two or three doses of the vaccine helped reduce mortality by a factor of 45.6 (Figure 2D).
It is worth noting that all the children who died had underlying diseases. As a result, in the fifth round of the outbreak, people mistakenly believed that Omicron BA.2 caused many deaths in Hong Kong or caused more serious diseases in children, but the opposite is true, and the case of Omicron BA.2 infection in Children in Hong Kong is the same as in other parts of the world, mostly mild or asymptomatic. In addition, vaccination is the most effective way to protect children from COVID-19 infection, i.e. severe COVID-19 or death.
04.
In the fifth outbreak, rapid antigen testing played an important role in identifying infected people and ensuring that the work environment was free of virus contamination.
At the beginning of infection, the viral load will quickly rise to a higher level, at which point both nucleic acid detection and antigen detection can detect infected people well at this stage.
During convalescence, nucleic acid testing can detect more patients with Ct values >25. But most of these people already have neutralizing antibodies and are no longer contagious.
While a positive antigen test is better associated with viral shedding and infectivity, antigen testing is more helpful in identifying infected individuals, especially those who are potentially super-spreaders. The pooled results of a daily antigen test within 5 days are more sensitive and reliable in the early diagnosis of COVID-19 infection than once or twice in 5 days for nucleic acid testing.
In Hong Kong, for example, antigen detection is more sensitive and specific in such an environment, and antigen detection can produce results within 15 to 20 minutes, which can quickly diagnose and isolate infected people.
In the early days of the fifth outbreak, thousands of people lined up for hours to do nucleic acid testing, which provided an opportunity for the virus to spread. At the same time, due to the large amount of detection, the turnaround time of nucleic acid detection is long, ranging from 3 to 7 days, which makes nucleic acid testing meaningless and a waste of resources.
As mentioned earlier, Omicron BA.2 infection progresses very rapidly. 3 days after the nucleic acid test results were issued, the infectivity of the people tested had been greatly reduced. After 5 days, they have basically fully recovered and cleared the virus. At this time, antigen detection is more practical.
In the fifth round, many people discussed the need for large-scale mandatory nucleic acid testing. There has been a proposal in Hong Kong to follow Shenzhen's example and conduct three consecutive rounds of nucleic acid testing for everyone over three weeks or nine days, but this is very expensive, and people need to wait for days to get the nucleic acid test results, this proposal is not practical. In addition, for the need to avoid gathering, insufficient isolation facilities, and too many infected people, due to the large number of infected people, it is difficult to find all infected people through only three rounds of nucleic acid testing, and it is difficult to achieve zero after that.
An alternative recommendation is to have everyone tested for antigens every day for 5 to 10 days. This initiative can also be implemented multiple times to achieve different goals, such as reducing infections and eliminating the virus in the community. The National Health Commission issued the "Guidelines for the Diagnosis and Treatment of Novel Coronavirus Pneumonia (Ninth Edition)" and also opened up antigen testing, as a supplement to nucleic acid testing, we believe that antigen testing will help China continue to fight the new crown epidemic.
05.
Fifth, Hong Kong's healthcare system has come under tremendous pressure during the fifth outbreak, but it has not collapsed and should not.
The large number of cases creates a huge burden. More than 15,700 (about 20 percent) of public hospital workers were infected, but as of March 17, 2022, half of them had returned to work.
People have been debating whether the health care system has collapsed, whether it is on the verge of collapse or has reached its limits. However, some have called on the public to protect the health care system from collapse, while others argue that the health system should have been built to protect people. In fact, these should be interdependent.
Our health care system can only protect people without collapsing. As mentioned earlier, since the start of the fifth wave, the total number of critically ill patients and ICU patients has been less than 300. The vast majority of patients are mildly ill and do not require special medical care. Many people are hospitalized just for prevention.
Therefore, if Hong Kong's healthcare system collapses in the fifth wave of the epidemic, it will inevitably be due to wrong judgments, wrong decisions and wrong resource allocation.
However, if all those who want to be hospitalized can be hospitalized, this is not possible, and this message must be clearly communicated to every stakeholder.
Prior to the fifth outbreak, we took a Ct value of 45 to determine if an infected person should be discharged from the hospital. People who had recovered but tested positive again were also recalled to hospitals, which led to excessive use of beds by people without medical needs at the beginning of the fifth outbreak.
In response to the rapid increase in confirmed cases, we lowered the discharge criteria to a Ct value of 33 and later to 30. Finally, ct values are used only as a reference, and if the attending physician judges that discharging the patient is beneficial to the patient, close contacts, and the community, the patient can be discharged.
We must have an appropriate risk assessment and triage system in place to hospitalize only patients who really need medical assistance and make the most of medical resources.
For a period of time, hospitalizations were prioritized for the elderly (Figure 2B), pregnant women, people with underlying medical conditions, and children. This method was later refined to further classify these patients according to risk factors.
Risk assessment and triage systems help protect healthcare systems so that both COVID-19 and non-COVID-19 patients are well cared for and treated. In order to respond to the ongoing fifth outbreak and other outbreaks that may arise in the future, we need to make further improvements to this system. In that regard, how to mobilize adequate resources is an important task now and in the future.
Many non-hospitalized patients with milder symptoms have anxiety or other mental health problems and are also victims of misinformation. Their medical needs are met at designated public clinics. In addition, a hotline has been set up to provide counselling and report on dangerous signs and symptoms.
Ideally, doctors, psychologists, psychiatrists, and social workers should work together to provide better support to patients. In this regard, virtual online consultation will be an attractive option. If the vast majority of people can feel happy and stay physically and mentally healthy, our fight against the pandemic will be more successful and our society will be stronger. Better communication is key in this process.
06.
Sixth, in the fifth round of the outbreak, home isolation is a viable option for many people.
Home isolation is not only cost-effective, but also achievable for many infected people and their close connections. As infection control measures have intensified, cluster outbreaks in households, which are more common in early outbreaks, occur in only one third to one-fifth of reported cases, and the incidence within the home is low.
In addition, the time required for home isolation or home health monitoring should also be shortened due to the shortened time window for virus shedding for Omicron BA.2 breakthrough infection.
With the friendly help of the mainland, Hong Kong has also rapidly established isolation facilities and cabin hospitals in addition to university dormitories, hotels and public residences. However, due to the very large number of cases and close contacts, isolation facilities will never be sufficient. Home isolation and home health monitoring are the only options.
The fifth round of the outbreak came from an accidental infection in the quarantined hotel, which reminds us of the need to focus on ventilation and infection control in the quarantine facilities. Consideration could be given to leaving public isolation facilities to those who need to live with high-risk family members or who lack space to live alone. And even in isolation at public facilities, you shouldn't stay too long. Reducing quarantine time in public facilities allows you to make the most of valuable resources without increasing the risk of accidental infection.
Finally, in areas where most people have not yet been exposed to the Omicron strain, the likelihood of a large outbreak of Omicron is relatively high, so it is necessary to be prepared for such an outbreak. When as many people in the world as possible are vaccinated and some immunity to Omicron is gained through natural infections, it is possible to see the end of the COVID-19 pandemic.
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Planner: Fy, Gyouza| Producer: Gyouza
Title image source: Journal screenshot