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Home ColumnEasy Explanation of the Latest Information on COVID-19 Vaccines (June 2021)

Easy Explanation of the Latest Information on COVID-19 Vaccines (June 2021)

Easy Explanation of the Latest Information on COVID-19 Vaccines

"There are various company vaccines, but what are the differences?" "How effective is the vaccine once administered?" "Why is the Delta variant so concerning?" This article addresses such questions.
We have compiled highly reliable information, primarily from primary sources such as public institutions and research centers.

Table of Contents

Understanding Vaccines Protects Your Health and Assets

Correct knowledge about vaccines protects your assets and health.

This is because there has been an increase in fraud related to the novel coronavirus.

For example, in Japan, the National Consumer Affairs Center has seen an increase in inquiries.

In the United States, there is also caution against fake treatments.

By reading this article and trying to gain correct knowledge, we absolutely do not want you to be deceived.

Correct knowledge about vaccines will help you avoid unapproved drugs and scams.

Three Types of Vaccines Approved in Japan (June 2021)

As of June 2021,

  • Pfizer/BioNTech vaccine
  • AstraZeneca vaccine
  • Moderna vaccine

are the three types of vaccines approved in Japan.

The first to be administered was the Pfizer/BioNTech vaccine.

Vaccination for healthcare workers began on February 17, 2021.

On May 21, 2021, the Moderna and AstraZeneca vaccines were approved.

Vaccination with the Moderna vaccine began on May 24, 2021.

As mentioned later, the Pfizer/BioNTech and Moderna vaccines are mRNA vaccines.

The AstraZeneca vaccine is called a viral vector vaccine, which is different in production method from mRNA vaccines.

The vaccine said to cause blood clots is the AstraZeneca vaccine.

Furthermore, the Johnson & Johnson vaccine, which has recently been frequently mentioned in the media, is still in the application stage and has not yet been supplied.

[Vaccine Mechanism] Vaccination to Make the Body Produce Antibodies

The vaccines approved in Japan are administered with the purpose of "making the human body produce antibodies."

When there are antibodies against the virus in the human body, it becomes less likely for the person to develop COVID-19.

Antibodies are proteins that neutralize the virus when it enters the body.

The purpose of the three types of vaccines is to "make the human body produce antibodies," but the methods of achieving this purpose differ.

The methods of achieving this purpose are through mRNA (messenger RNA) and viral vectors.

In this section, we will explain the mechanisms of mRNA vaccines and viral vector vaccines.

Infection and Development are Not Required to Produce Antibodies

The condition for the human body to produce antibodies is to be infected with and develop COVID-19.

However, you wouldn't want to get infected with and develop COVID-19 for that purpose, right?

Vaccines were developed as a way to make the human body produce antibodies without being infected with and developing COVID-19.

In other words, the whole virus is not necessarily required for the body to produce antibodies.

Vaccination is to Make the Body Produce Spike Proteins

A vaccine is a method of introducing the blueprint for the spike protein※1 into the human body.

To produce antibodies against the novel coronavirus, the human body needs to recognize the spike protein of the virus.

Therefore, the spike protein needs to be introduced into the human body.

When the blueprint for the spike protein is introduced into the body, the human body produces the spike protein based on this blueprint.

Using the spike protein as a marker, the human body produces antibodies and can prevent the infection and development of COVID-19.

※1 Spike protein: A protein on the surface of the novel coronavirus. The virus can infect humans because of the spike protein.

The Difference Between mRNA Vaccines and Viral Vector Vaccines is the Delivery Method

The tool used to introduce the blueprint for the spike protein into the human body and make it produce antibodies is the vaccine.

The difference between mRNA vaccines and viral vector vaccines lies in how the blueprint is delivered.

The spike protein cannot be produced from the blueprint unless it is delivered to human cells.

mRNA vaccines contain the information for the spike protein within a lipid membrane (lipid nanoparticles).

Viral vector vaccines use a chimpanzee adenovirus to carry the information for the spike protein, delivering the blueprint to the cells.

Advantages and Disadvantages of mRNA Vaccines

The advantages of mRNA are:

  • It does not take long to produce
  • Even if vaccinated, you will not get COVID-19
  • There is no worry that your own DNA will be rewritten by mRNA

The reason for the shorter production time is that, unlike traditional vaccines, it does not require the cultivation of the virus.

mRNA vaccines only contain information about the spike protein on the surface of the novel coronavirus.

With just that information, the symptoms that appear with COVID-19 do not manifest.

mRNA vaccines are broken down within a few days.

Since it does not stay in the body, the information of the spike protein is not incorporated into human DNA.

However, the disadvantages include:

  • There may be unintended side effects
  • Storage and management are challenging

Advantages and Disadvantages of Viral Vector Vaccines

The advantages of viral vector vaccines are:

  • Even if vaccinated, you will not get COVID-19
  • Easier to store and manage compared to mRNA

On the other hand, the disadvantages include the possibility of developing immunity to the viral vector.

If that happens, the vaccine may be eliminated from the body before the person can produce antibodies.

Furthermore, if immunity is developed after the first dose, the second dose may also be eliminated from the body, potentially preventing the vaccine from having its full effect.

Vaccine Effectiveness and Duration

The efficacy rates of the three vaccines are all high.

Specifically,

  • Pfizer/BioNTech: 94.6%
  • Moderna: 94.1%
  • AstraZeneca: 70.4%

The duration of the vaccine's effectiveness is said to last about six months.

According to data released by Moderna, antibodies remain in the body even 180 days after the second dose.

Pfizer also investigated the prevention efficacy six months after the clinical trials.

The results showed that the prevention efficacy was maintained at a high level of 91.3%.

Differences in Vaccine Types

mRNA vaccines have an efficacy rate of over 90%.

Viral vector vaccines also show an efficacy rate of over 70%, which is higher than that of influenza vaccines.

In this section, we will explain the differences between the three approved vaccines,

  • Pfizer/BioNTech (mRNA vaccine)
  • Moderna (mRNA vaccine)
  • AstraZeneca (viral vector vaccine),

aside from their efficacy rates.

Differences in Production Methods

Moderna and Pfizer/BioNTech

encapsulate the spike protein information within a lipid membrane.

This is because mRNA is very unstable and easily broken.

The lipid membrane has the role of protecting the mRNA.

AstraZeneca

incorporates the spike protein information into a chimpanzee adenovirus.

The adenovirus is processed so that it does not replicate within the human body.

The reason for using a chimpanzee adenovirus is that humans do not have immunity to it.

Humans have immunity to human adenoviruses and will try to eliminate them.

However, in the case of the chimpanzee adenovirus, it is not eliminated and can enter the cells.

Handling Methods

mRNA vaccines and viral vector vaccines have different storage temperature requirements.

mRNA vaccines are more delicate and difficult to handle, requiring storage at lower temperatures.

At 2-8°C, the Pfizer/BioNTech vaccine can be stored for 5 days, and the Moderna vaccine for about 30 days.

For long-term storage, it is necessary to store them at -20°C or lower.

In contrast, the AstraZeneca vaccine (viral vector vaccine) can be stored at 2-8°C for up to 6 months.

Because its management is similar to that of the influenza vaccine, it is expected to be easier to distribute.

Side Effects

Common side effects among the three vaccines are:

  • Pain at the injection site
  • Fatigue
  • Headache
  • Fever
  • Muscle pain

In addition to the above, anaphylactic shock has also been observed with the Pfizer/BioNTech and Moderna vaccines.

A rare side effect of the AstraZeneca vaccine is 'blood clots.'

Blood clots are when the blood solidifies or becomes thick and sticky.

When blood clots are present in the blood, the flow of blood becomes poor, which can lead to various diseases.

What are the Blood Clots Caused by the AstraZeneca Vaccine?

When vaccinated with the AstraZeneca vaccine, TTS may rarely occur.

TTS stands for Thrombosis with Thrombocytopenia Syndrome, which is thrombosis with thrombocytopenia following vaccination.

TTS is said to develop 4 to 28 days after vaccination and is characterized by:

  • Thrombosis
  • Thrombocytopenia
  • Abnormal coagulation and fibrinolytic system markers
  • Detection of anti-platelet factor 4 antibodies

The incidence of TTS is low, occurring at a rate of 1 in 10,000 to 1 in 100,000 people.

TTS can lead to severe cerebral venous thrombosis with symptoms such as bleeding and brain edema, and it has a very high fatality rate.

Target Population for Vaccination

The Moderna and AstraZeneca vaccines are for those aged 18 and older.

Since June 2021, the Pfizer vaccine has been approved for those aged 12 and older.

Development and Approval Process of Vaccines

Vaccines cannot be distributed immediately after they are developed.

They take many years to be supplied to us.

However, compared to traditional vaccines, the COVID-19 vaccines were supplied in a short period of time.

In this section, we will explain the differences between the COVID-19 vaccines and traditional vaccines.

The Process of Supplying Traditional Vaccines

The general process leading to vaccine supply includes:

  • Basic research
  • Preclinical trials
  • Clinical trials
  • Regulatory submission and review
  • Approval

Basic research is the stage where it is decided what to use to create the vaccine.

Traditionally, viruses were weakened and grown to be used as vaccines (live attenuated vaccines, inactivated vaccines).

Achieving this took a lot of time, as it involved virus cultivation.

Preclinical trials involve using the vaccine developed in basic research on cells and animals to observe the results.

Based on this trial, the dosage for humans is roughly determined.

Clinical trials involve actual administration to humans and typically consist of three phases.

Phase 1 administers the vaccine to a small number of healthy individuals.

Phase 2 starts administering the vaccine to a small number of target individuals.

Phase 3 administers the vaccine to a large number of target individuals based on the results obtained up to phase 2 and confirms the outcomes.

This process is generally referred to as clinical trials.

Regulatory submission and review involve submitting the data obtained from clinical trials to the Ministry of Health, Labour and Welfare (MHLW).

The review is conducted by the MHLW, and the review period is approximately less than a year on average.

Through these steps, vaccine use is approved, and it is supplied to us.

The Process of COVID-19 Vaccines

A major difference from traditional vaccines is that each step was conducted simultaneously, shortening the period.

For the COVID-19 vaccines, basic research and clinical trials were conducted at the same time, reducing the time until regulatory submission.

Next, mRNA vaccines could quickly complete the basic research stage.

This is because there is no period required for virus cultivation, as in traditional methods.

Furthermore, the Ministry of Health, Labour and Welfare shortened the review period compared to traditional vaccines.

Regarding vaccine production, the government supported the development companies to increase speed.

The government bore the risk for the development companies, allowing research, development, and production to proceed in parallel.

This "Accelerated Parallel Plan" is an unprecedented approach by the Ministry of Health, Labour and Welfare to realize COVID-19 vaccines early.

Antibodies Form When Infected with COVID-19

Like vaccines, antibodies can be produced even if infected with COVID-19.

However, according to a statement by the Ministry of Health, Labour and Welfare, "Antibodies are produced, but the period during which antibodies remain is not clear."

There have been several reports regarding the duration antibodies remain in the body.

According to reports from Yokohama City University and the Japan Agency for Medical Research and Development, antibodies are maintained for 3-6 months.

On the other hand, Osaka University has reported that not all antibodies neutralize the virus; some may enhance infection (infection-enhancing antibodies).

Why is the Delta Variant so Threatening?

The reasons why the Delta variant (India variant) is perceived as a threat are:

  • The scenes of medical collapse in India amplify the threat
  • Animal experiments show that its pathogenicity is higher than that of the original virus
  • It is suggested that the Delta variant (India variant) has increased infectiousness, especially for Japanese people

The number of new infections in India exceeds 300,000 to 400,000 per day on average, with more than 300,000 deaths during the pandemic.

In the medical field, there is a shortage of medical oxygen and medicines.

Regarding pathogenicity, experiments were conducted on hamsters, not humans.

The experiment involved infecting hamsters with the original COVID-19 virus and the Delta variant (India variant).

The results reported that the Delta variant has higher pathogenicity than the original COVID-19 virus.

A characteristic of the Delta variant (India variant) is "double mutation."

"Double mutation" refers to the simultaneous occurrence of mutations L452R and E484Q in the spike protein of the COVID-19 virus.

"Double mutation" allows the virus to evade the human immune system, increasing its infectiousness.

Why is it more infectious to Japanese people?

It is because the COVID-19 virus can escape from the immune system commonly found in Japanese people.

About 60% of Japanese people have white blood cells with "HLA-A24."

White blood cells are immune cells, and "HLA-A24" is the blood type of these white blood cells.

In other words, the Delta variant (India variant) with "double mutation" has the ability to easily escape from "HLA-A24," making it more infectious to 60% of Japanese people.

References