It looks like the "8th wave" of the new corona has finally peaked out.
What will happen in the future is the mutated virus, "XBB.1.5", which is likely to influence the situation.
In the United States, the rate is over 60%, and it is said that immunity is difficult to work and that it is easy to spread.
Will "XBB.1.5" prolong the "eighth wave"?
Do current vaccines work?
What is the "9th wave"?
I have summarized what I have learned.
(As of February 1)
Beware of mutated viruses even in the transition to "Type 5"
"Quite a number of attendees expressed the opinion that the new coronavirus continues to change and caution is necessary,"
a press conference held on January 27.
Shigeru Omi, chairman of the government subcommittee, said, stating that it is necessary to continue to be vigilant against mutated viruses.
On this day, the government decided to classify the novel coronavirus under the Infectious Diseases Control Law as "type 5", the same as the influenza epidemic that occurs every year in May.
"If a mutation occurs that greatly enhances pathogenicity, or if a situation occurs in which even if the Omicron strain is the same strain, no matter how hard you try, a medical emergency occurs, I think it will be necessary to review the response."
XBB.1.5 Continues to expand in the US
As a new mutation, "XBB.1.5" is particularly alarming.
In the United States, the number of cases has increased sharply since around December last year, mainly in eastern areas such as New York, and is believed to have accounted for 61.3% in the week until January 28 (CDC = Centers for Disease Control).
"XBB.1.5" is a mutant virus "XBB" that combines two types of "BA.2" that spread from around the spring of 2022 among the Omicron strains, and further mutations have been added.
According to the weekly report of WHO = World Health Organization on January 25, "XBB.1.5" has been reported in 54 countries so far.
By country, the United States accounts for the majority at 75.0%, followed by the United Kingdom at 9.9%, Canada at 3.0%, and Denmark at 2.0%.
On the other hand, according to the materials of the monitoring meeting of the Tokyo Metropolitan Government, 31 cases have been confirmed in Tokyo since the beginning of December, but the detection rate was 0.1% even in the week leading up to January 9. It's not an increasing situation.
WHO Risk Assessment “Possibility of increasing the number of infected people worldwide”
On January 25, WHO published an updated risk assessment for 'XBB.1.5'.
According to that,
▼ Regarding the spread of the virus, data from the United States, the United Kingdom, and European countries indicate that it is easier to spread than other Omicron strain mutant viruses.
▼ It is said that the property of escaping immunity obtained from past infections and vaccinations is the strongest among the mutated viruses so far.
However, in people who have been vaccinated against the Omicron strain "BA.5" or who have "hybrid immunity" who have been vaccinated and have been infected, "XBB.1" similar to "XBB.1.5" It is said that the antibody value for "is high.
▼ It is said that there are no signs in the early stages that the severity of infection is increasing.
WHO says that 'XBB.1.5' 'may lead to an increase in the number of infected people worldwide.'
Professor Hiroshi Nishiura of Kyoto University, who specializes in mathematical epidemiology, said at an expert meeting of the Ministry of Health, Labor and Welfare on January 17 that the effective reproduction number, which indicates "how many people one person infects," has been the mainstream worldwide. It shows a trial calculation that it is 1.47 times higher than "BA.5", which was formerly (analyzing data up to January 14).
Atsuro Hamada, a specially appointed professor at Tokyo Medical University who is familiar with the situation of overseas infections, said, "The WHO is also cautious, but the number of infected people in the world is not increasing, and we are still analyzing how infectious it is. On the other hand, the death toll remains high in the U.S. The number of reported infections is not increasing, but the number of cases is actually increasing to some extent. We have to consider the possibilities,” he said.
Immune evasion "Maximum" Binding strength "Strengthen"
Studies on "XBB.1.5" have also been published.
A researcher group "G2P-Japan" led by Professor Kei Sato of the Institute of Medical Science, the University of Tokyo, created a virus artificially by reproducing the characteristics of "XBB.1.5" as a paper before being peer-reviewed. I published the results of the experiment.
After vaccination, the research group used the blood of people infected with the Omicron strain `` BA.5 '', which was the mainstream in the 7th wave after the summer of 2022, to investigate the immune response to `` XBB.1.5 ''. I was.
As a result, the activity of the neutralizing antibody that suppresses the virus was only about 1/10th of that against BA.5, demonstrating its ability to escape immunity.
In addition, the research group believes that the infectivity may also be increasing.
When the new coronavirus infects humans, it attaches to a protein called ACE2 on the surface of cells.
The easier it is to stick to human cells, the higher the infectivity.
"XBB.1.5" has a new mutation "F486P".
According to Professor Sato, with this mutation, "XBB.1.5" had a 4.3-fold increase in the ability to bind to proteins on the surface of cells compared to the mutant virus without the type.
In previous mutant viruses, it was difficult to achieve both ``escape from neutralizing antibodies'' and ``increase binding strength'', but ``XBB.1. doing.
(Professor Sato)
"It is thought that the addition of further mutations to 'XBB', which had an increased ability to evade immunity and was, so to speak, a 'completed form', has increased the ability to infect cells, making it easier to spread. So far, there have been very few mutations.”
Will the vaccine remain effective?
On the other hand, an analysis result was issued in late January that the effect of preventing the onset of the vaccine was maintained against "XBB.1.5".
It was announced by the CDC = Center for Disease Control in the United States.
From December to mid-January 2022, the CDC investigated the vaccination status of those who were tested for the new corona, and analyzed the effects of vaccines against XBB lineage mutant viruses such as ``XBB.1.5''.
As a result, after multiple doses of the conventional vaccine, additional vaccination with a vaccine containing the component corresponding to the Omicron strain BA.5 is more effective in preventing the onset of the XBB lineage virus than without the additional vaccination.
▼ 49% for those aged 18 to 49,
▼
40% for those aged 50 to 64, and
▼ 43% for those aged 65 and over.
The CDC says that booster vaccinations for the Omicron strain will be more effective in reducing the symptoms of XBB and XBB.1.5, and that people who are able should get the latest boosters increase.
There is a report that the function of antibodies produced by vaccination and infection against "XBB.1.5" is reduced, but recently, analysis results have been issued that the body's immune cells maintain the ability to eliminate the virus. I was.
Research groups such as "Beth Israel Deaconess Medical Center" in Boston, USA, used the blood of people who received a booster vaccine corresponding to the Omicron strain to investigate the function of immunity against "XBB.1.5". The results were published in late January as a paper before being peer-reviewed by a third party.
As a result, 3 months after the booster vaccination, the level of neutralizing antibody against "XBB.1.5" decreased to 1/16th of that against "BA.5", which was almost the same level as before vaccination. .
On the other hand, the value indicating the function of cell-mediated immunity was about the same as that of the conventional virus and ``BQ.1.1'', which is a mutation added to ``BA.5''.
Specially appointed professor Tetsuo Nakayama of Kitasato University, who specializes in clinical virology and is familiar with vaccines, said, "In response to 'XBB.1.5,' the function of antibodies is reduced, but cell-mediated immunity is thought to be maintained. According to data from the real world, there is a report that the Omicron strain vaccine is effective in preventing the onset of disease by about 50%.It is believed that vaccination is sufficiently effective in suppressing the onset and severity of infection even if infected. It does not mean that a further booster vaccination is necessary, but if you have already received a booster vaccination against the Omicron strain, you will be able to cope sufficiently. I want it," he says.
Mutant viruses are “coexisting”
"XBB.1.5" is considered to be highly contagious and easy to escape from immunity, but so far it has not spread widely outside the United States.
Also, in the world, and in Japan as well, a specific mutated virus does not account for almost everything, so to speak, various viruses coexist.
According to the data presented at the monitoring meeting in Tokyo, all of the mutant viruses detected in the week leading up to early January are one of the Omicron strains
. Mainstream from summer)
▽ ``BF.7'' 16.2% (mutation added to ``BA.5'' expanding in China)
▽ ``BQ.1.1'' 16.1% (mutation added to ``BQ.1'')
▽ ``BN.1'' 10.5 % (Mutation added to "BA.2.75")
▽ "BQ.1" 3.4% (Mutation added to "BA.5")
▽ "BA.2.75" 3.4% (Mutation added to "BA.2")
▽ "BA 2” 1.5% (mainstream from spring to summer 2022)
▽ “XBB” 0.2%
▼ “XBB.1.5” 0.1%
.
Will it lead to a resurgence of infection?
The “8th wave” that has continued since the fall of last year (2022) seems to have finally passed its peak, but if “XBB.1.5” further inflows, the “8th wave” will be prolonged and the “9th wave” Will it connect?
Shigeru Omi, chairman of the government subcommittee, said in NHK's "Close-up Gendai" broadcast on January 24, ``If XBB.1. I think it's better to keep in mind that there is a possibility that the so-called '9th wave' will come after it recurs or has completely declined."
The Biden administration in the United States announced on January 30 that it will lift the national emergency declaration on the new corona that has continued since 2020 on May 11.
On the other hand, WHO held a committee of experts on "Public Health Emergency of International Concern" on January 27 and decided to maintain the state of emergency issued at the end of January 2020. rice field.
In a statement issued by the WHO after the committee meeting, the mutated virus of the Omicron strain, which is currently spreading, "compared to the mutated virus so far, tends to be less severe, but has unpredictable characteristics. It retains the ability to evolve into a new mutant virus with
WHO is calling on countries to promote booster vaccinations and continue to be vigilant against mutated viruses.
Hamada, a specially appointed professor at Tokyo Medical University, said that by moving to "Type 5" in Japan in the future, it will be more important than ever for individuals and companies to make decisions to prevent the spread of infection.
(Professor Hamada)
"There are still few cases of 'XBB.1.5' being detected in Tokyo, but it is expected that the number of arrivals from the United States and other countries will increase in the future. Now, the '8th wave' is peaking. Although it is out, there is a possibility that it will lead to a wave of infection in the form of a 'ninth wave'.
" Regulations on isolation and medical treatment will also disappear, but since the new coronavirus cannot be left unchecked, companies will have to make their own judgments and create countermeasures, similar to the flu regulations. The vaccine seems to be effective against "XBB.1.5", so if you haven't been vaccinated, please take it.When the infection spreads after mitigation progresses in Europe, wearing a mask on public transport is recommended. We took measures according to the situation, such as asking for it.It will be necessary for Japan to respond while monitoring the epidemic situation."