Vol.15 (2020/11/10) Results of antibody tests at our clinic / Decline in antibody possession rate among infected individuals / Differences in fatality rates between countries and regions / Cases of mass infection at drinking parties / etc.

[1] The antibody possession rate in blood tests at our hospital

At our clinic, we only conduct tests on people who have no symptoms such as fever or cough (have not had any within the past two weeks), and the positive rate of COVID-2 antibody tests at our clinic (from September 9th to October 15th) was 10% (14 out of 1.47 cases).
In addition, the positive rate since testing began on June 6 has remained roughly constant at 15% (1.44 out of 1811 cases).

(Figure 1) Trends in antibody testing at our clinic

[2] Japan and the world: Trends in the number of infected people

The number of cases continues to increase worldwide. Japan may be facing a third wave of infections.

(Figure 2) Cumulative number of COVID-XNUMX infections (worldwide)

(Figure 3) Number of new infections by day (Japan)

Source: (Figure 2) World: Ministry of Foreign Affairs COVID-XNUMX infection status in each country and region
https://www.anzen.mofa.go.jp/covid19/country_count.html
(Figure 3) Japan: Yahoo! COVID-XNUMX Summary
https://hazard.yahoo.co.jp/article/20200207

[3] A paper showing that the antibody retention rate of infected individuals decreases over time

Healthcare workers and emergency staff in New York City and Detroit who were diagnosed with COVID-2 as a result of PCR testing were tested for IgG antibodies against the COVID-XNUMX spike protein two weeks or more after the onset of symptoms.
After a positive PCR result, antibody levels increased in 95% of cases, and the antibody possession rate began to decrease after three months.

(Figure 4) Trends in antibody possession rates

Source: IgG antibody disappearance rate in people previously infected with COVID-19
Lack of antibodies to SARS-CoV-2 in a large cohort of previously infected persons. Clin Infect Dis. 2020 Nov 4
https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa1685/5956137
(Figures and tables created by the author based on papers)

[4] People who have had a cold before may be at lower risk of contracting COVID-19

Now, there is a research paper that looks into the correlation between COVID-19 and illnesses caused by other common cold coronaviruses.
Research has shown that people who have experienced cold symptoms such as sinusitis, bronchitis, or pharyngitis in the past four years have a lower positive rate for COVID-4 PCR tests, and this may also be related to the age group of the patient.

background:

There may be cross-immunity between seasonal coronaviruses and SARS-CoV-2, and humoral and cellular immunity to SARS-CoV-2 has already been demonstrated in blood before the pandemic.

method:

Based on health insurance medical records, medical history, and test data, we conducted a cohort study of 869,236 people who underwent PCR testing for COVID-XNUMX. We analyzed the association between PCR positivity and various symptoms and diseases in the previous year that may be related to the results.

(Figure 5) Protective effect over time against common cold symptoms

The graph above shows that people who have experienced cold symptoms (sinusitis, bronchitis, pharyngitis) in the last four years had a lower positive rate of COVID-4 PCR tests.
The more severe the symptoms and the more recent the infection, the lower the positive rate of coronavirus tests, but only up to about 5%.

(Figure 6) Odds ratio of a positive PCR test for SARS-CoV-2 by age group

The figure above shows that this reduction effect was clearly observed in people over 30 years old, but not in younger people. In people between 30 and 70 years old, the odds ratio was about 0.8, indicating that the positive rate of coronavirus tests decreased by about 20%.
People over 30 years old have immune memory from previous coronavirus infections, and it is possible that the stimulation of the immune system from a recent cold may have had some effect on the COVID-XNUMX infection.
The fact that the previous figure showed only a 5% decrease may be related to the fact that many of the infected people were young people.

Source: Prior Presumed Coronavirus Infection Reduces COVID-19 Risk: A Cohort Study.
J Infect. 2020 Oct 27:S0163-4453(20)30683-6
https://www.journalofinfection.com/article/S0163-4453(20)30683-6/fulltext

[5] Comparison of COVID-19 mortality rates between Singapore and Japan

Next, we will compare the results by country.
Singapore is known to have an extremely low mortality rate among patients infected with COVID-19 compared to other countries.
The age-adjusted mortality rates for people in their 60s and 70s were 1.84% and 5.57%, respectively, in Singapore, compared with 5.52% and 15.49% in Japan.
Please note that the graph below is a logarithmic graph, but it clearly shows how low Singapore's death rate is compared to countries with low death rates around the world, such as New Zealand, South Korea, and Japan.
It is not yet clear whether this difference is due to Singapore's high rate of patient detection through PCR or the characteristics of the virus.

(Figure 7) Crude fatality risk of COVID-19 (by country)

Source: A Comparison of Case Fatality Risk of COVID-19 between Singapore and Japan.
J Clin Med. 2020 Oct 16;9(10):
https://www.mdpi.com/2077-0383/9/10/3326/htm

[6] The more elderly people are infected, the higher the mortality rate: Comparison in Europe and the United States

Following the comparison between Japan and Singapore, we turn now to a comparison with Europe and the United States.
A comparison between Europe, the United States, and Canada has shown that the mortality rate is higher in countries with a higher proportion of infected people aged 75 and over.
(The size of the circles reflects the country's number of COVID-100 related deaths per million inhabitants.)

(Figure 8) Relationship between case fatality rate (CFR) of COVID-75 and the proportion of people aged XNUMX years or older

Source: Older age groups and country-specific case fatality rates of COVID-19 in Europe, USA and Canada. Infection. 2020 Oct 24
https://link.springer.com/article/10.1007/s15010-020-01538-w

[7] Genes related to COVID-19 severity may be of Neanderthal origin

Data is beginning to show that the mortality rate of COVID-19 varies greatly between countries and regions, and one study has pinpointed genetic factors as one of the factors.

A COVID-3199 Host Genetics Initiative study of 19 hospitalized COVID-3 patients and controls found that a gene cluster on chromosome XNUMX was more prevalent among hospitalized severely infected COVID-XNUMX patients.
Provenance analysis revealed that this genomic segment, containing 5 bases, was inherited from Neanderthals.
Currently, 50% of people in South Asia and 16% of people in Europe carry these genes.
There seems to be very little of it in East Asia.

(Figure 9) Prevalence of genes related to COVID-XNUMX severity derived from Neanderthals (red part of pie graph)

Source: The major genetic risk factor for severe COVID-19 is inherited from Neanderthals.
Nature. 2020 Sep 30.
https://www.nature.com/articles/s41586-020-2818-3

[10] On October 28, the National Institute of Infectious Diseases announced a case of COVID-XNUMX infection at a drinking party.

In any case, the only way to overcome this virus is to thoroughly take precautions against infection on a daily basis.
Today, we will introduce all six cases of mass infections occurring at drinking parties compiled by the National Institute of Infectious Diseases, as material for considering infection prevention measures. Specific scenes are described, such as the number of participants, seating layout, participation time, ventilation information, etc.
The "lessons learned" contained here are information you can use starting today. Please use them as a reference.

<Research Methodology>

・Based on requests for support from local governments, we conducted a review of cases of mass infections* that occurred at drinking parties among the field epidemiological investigations that were supported by staff from the Infectious Disease Epidemiology Center of the National Institute of Infectious Diseases and trainees from the Field Epidemiology Training Program (FETP) between February and October 2020, 2.

・Organize findings and lessons learned from the survey

<Result>

☑ Case A: Dining at a table

☑ Case B: All attendees at a drinking party attended by a pre-symptomatic case tested positive

☑ Case C: At a drinking party attended by a pre-symptomatic case, half of the approximately 15 people in multiple groups who were present tested positive.

Case D: Source of infection unknown. A customer and an employee who were in the same store developed symptoms at the same time and tested positive.

☑ Case E: A case in which a person dined in a private room with coworkers

☑ Case F: Drinking party with multiple people

☑6 Summary of Cases

<Summary>

Of the six cases A to F covered in this study, five were cases of transmission between customers in the same group, three were cases of transmission between customers in different groups, and two were cases of transmission between customers and employees.Guest-to-guest transmission was common.This trend was similar during regular dining out.

Regarding the two cases involving customers and employees, in case D, the employee was wearing a mask but had a lot of conversation with the customer (who was not wearing a mask) and was found to be infected. In case F, the employee (whether they were wearing a mask or not) was found to be infected because they had close contact with the customer (who was not wearing a mask), such as by sitting at the same table as the customer, staying there for a long time, and drinking alcohol.
Even if you wear a mask, if you have close contact with a customer who is not wearing a mask, such as by talking to them, in a situation where you cannot maintain a sufficient distance, it may not be possible to completely prevent infection.

・In addition, just like with regular dining out, the possibility of infection was thought to be high even in so-called "drinking parties" due to close contact, conversations without wearing masks, the continued work of symptomatic store staff, and poor ventilation in the store.

・On the other hand, the characteristics of so-called "drinking parties" are as follows:Transmission between guests from different groups was also observedIn cases where infection was transmitted to other groups, the following characteristics were observed: 1) the number of participants was large, and the environment was prone to crowding, 2) there was contact and conversation with many people (including people from other groups), 3) frequent seating changes, and 4) drinks were shared.(Drinking alcohol itself does not increase the risk of infection.)

<Recommendations>

In addition to the general infection prevention measures such as wearing masks, hand hygiene, managing employee health, maintaining physical distance, and frequently ventilating stores, we make the following recommendations based on what we have learned this time:

[Customer]

• ◦People who are feeling unwell should not attend events or parties.
• ◦ To minimize the risk of becoming a source of infection, avoid opportunities for infection (the 3 Cs), wear masks properly, and practice hand hygiene.
• ◦Do not share drinking containers (such as glasses)
• ◦ Avoid unnecessary contact with other groups

【employee】

• ◦ Layout and seating arrangements in the restaurant to avoid overcrowding (especially during banquets and events)
• ◦ Limit seat movement

Source: Cases of mass infection at so-called "drinking parties" National Institute of Infectious Diseases
https://www.niid.go.jp/niid/ja/diseases/ka/corona-virus/2019-ncov/2484-idsc/9941-covid19-26.html
The above chart: https://www.niid.go.jp/niid/images/epi/corona/covid19-26.pdf