January 30, 2023

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Can the second shot of COVID-19 vaccine be vaccinated in advance?

Can the second shot of COVID-19 vaccine be vaccinated in advance?


Can the second shot of COVID-19 vaccine be vaccinated in advance? Some people choose to get one dose or two doses at the same time due to tight time. Is this vaccination still effective?

Have you received COVID-19 vaccine?

China has successively vaccinated nine types of high-risk individuals with COVID-19, many of whom are working or studying abroad for business or private purposes. Some of them choose to get one dose or two doses at the same time due to tight time. Is this vaccination still effective?


COVID-19 vaccination interval

The official recommendation is two injections, at least 14 days apart.

On December 21, 2020, Wang Huaqing, chief expert of the China Centers for Disease Control and Prevention’s immunization program, introduced the immune mechanism of the COVID-19 vaccine after vaccination.

After vaccination, the body’s immune system mainly has T lymphocytes and B lymphocytes. This effect is mainly manifested in three aspects. One is the recognition of T lymphocytes and B lymphocytes after vaccination; the other is The role of immune memory; the third is to resist viruses or bacteria.

Wang Huaqing also said that from the previously published COVID-19 vaccine literature, the time for the COVID-19 vaccine to work is mainly two weeks after the second dose of the vaccine, which will produce a better immune effect.


Types of vaccines in China

At present, there are two types of COVID-19 vaccines that can be vaccinated in China: Sinopharm Sino Biotech (Beijing Institute and Wuhan Institute) and Kexing Zhongwei Inactivated Vaccine.

People who have been vaccinated generally know that each vaccine has its own specific vaccination schedule. The complete vaccination program should include the number of inoculation doses, time intervals, inoculation dose, inoculation route and inoculation site. Different vaccines have different time intervals, and this interval is also determined by experimental results!

We also have to rely on data to speak. Today, we have compiled the results of the COVID-19 vaccine experiment of Sinopharm and Kexing, let’s take a look ↓↓

The neutralizing antibody titer is closely related to the protective effect of the vaccine. The higher the neutralizing antibody titer, the higher the vaccine protection rate!

Experimental data

1. SINOPHARM vaccine

In October 2020, “The Lancet · Infectious Diseases” published the results of the Phase I/II trial of the COVID-19 inactivated vaccine developed by the Beijing Institute of Biological Products of Sinopharm Group. The results are briefly summarized as follows:

  • The standard dose interval is 21 days, and the neutralizing antibody titer is 282;
  • The standard dose interval is 14 days, and the neutralizing antibody titer is 169;
  • The standard dose interval is 28 days, and the neutralizing antibody titer is 217;
  • The high dose is only 1 shot, and the neutralizing antibody titer is 14.

Can the second shot of COVID-19 vaccine be vaccinated in advance? 

From the results of this experiment, we can see that it is best to vaccinate the COVID-19 vaccine with an interval of 21 days. If it is shortened to 14 days or extended to 28 days, the neutralizing antibody titer is lower, but it is basically an order of magnitude. , The conversion to actual efficiency may not be much different.

But if the two injections are used together, the neutralizing antibody titer is very low, and it may not be able to protect it!

2. Kexing (SINOVAC) vaccine

As an emergency vaccination, Kexing inactivated vaccine also published its Phase I/II clinical trial data in “The Lancet · Infectious Diseases” in November 2020.

One of the key points of Kexing’s Phase II clinical trial is whether the two injections should be separated by 14 days or 28 days. The results showed that compared with the 0-day/14-day vaccination schedule, the 0-day/28-day vaccination schedule produced a stronger antibody response, a higher neutralizing antibody titre, and an expected duration.

The figure below shows the neutralizing antibody titers of two vaccination intervals: 0/14 (left) and 0/28 (right):

Can the second shot of COVID-19 vaccine be vaccinated in advance?

The results published by Kexing show that:

▶The 0/14-day vaccination method can quickly induce neutralizing antibodies in a relatively short time, which is suitable for emergency vaccination, which is essential for high-risk areas.

▶The 0/28-day vaccination method produces a higher concentration of neutralizing antibodies and lasts longer, so in low-risk areas, it is recommended to use the 0/28-day vaccination method.


How the human immune system responds to vaccines

At present, the COVID-19 vaccines we can get are all inactivated vaccines. Inactivated vaccines use artificial methods such as heating to kill pathogens, but retain their original characteristics that can cause an immune response, and can also trigger an immune response after inoculation to the human body, thereby protecting the body.

The response of the human immune system to different pathogens is very different, and the response to vaccines is also different depending on the type of vaccine. The response of the human immune system to vaccines does not increase linearly, as shown in the figure below:

Can the second shot of COVID-19 vaccine be vaccinated in advance? 

The meaning expressed in the figure is that after the first vaccination, a low-level immune effect is produced, and when the vaccination is again, it will produce a much greater immune effect than the first time.

Zhu Fengcai, deputy director of the Jiangsu Provincial Center for Disease Control and Prevention, said: “If you get two shots in a day, you can only count as one shot. One shot is basically useless.” So friends, you should know how to get vaccinated?


Finally, let’s summarize:

If you are anxious to go abroad, whether it is Sinopharm or Kexing, you can consider the 14-day interval. Although the neutralizing antibody titer produced is far from the standard vaccination, it is basically sufficient.

If you are vaccinated normally and stay in the country after the vaccination, please follow the standardized vaccination method and the interval between the two injections is long enough (21 days or 28 days).

There is no specific data to indicate how long the vaccination can be delayed, but it is recommended that the interval is not too long, which will increase the risk of infection.

How to replant if the second dose is missed or delayed?

At present, clinical research data of different immunization procedures have not been obtained, so the maximum interval between two doses of COVID-19 inactivated vaccine has not been determined. If you miss the time of vaccination, it is recommended to make up the corresponding doses as soon as possible.

Is it necessary for people who have had COVID-19 pneumonia or asymptomatic infection to receive the COVID-19 vaccine?

Based on the existing published information, the results of gene sequencing in Hong Kong, Belgium, the Netherlands, the United States and other places have found re-infection phenomena, and it is impossible to draw a conclusion of life-long immunity for an infection.

But generally speaking, people who have been infected with infectious diseases or asymptomatic infections will produce corresponding antibodies, which should have a protective effect similar to vaccination. It is recommended that people who have recovered from COVID-19 pneumonia or those who are asymptomatically infected should not be vaccinated.

Can seafood/eggs/penicillin allergy be vaccinated against the COVID-19 vaccine?

People who are known to be allergic to any of the components of the vaccine; pregnant women; or those who have had allergies from previous vaccination with this vaccine; patients with fever, acute disease and acute chronic disease should postpone vaccination.

Seafood/eggs/penicillin is not any component of the COVID-19 vaccine, so you can consider vaccination.

Do I need to check for antibody production?

not recommend!

Due to the different detection methods and the sensitivity of related reagents, the results may not show true information. Combined with the laboratory test results of the vaccine research and development institution, it can be inferred that the positive conversion rate of neutralizing antibodies exceeds 90%.

Therefore, except for those with special needs, there is no need for special antibody testing, and it is not recommended to replant for people with negative antibody test results.

Will the nucleic acid test be positive after being vaccinated with the COVID-19 vaccine?

will not.

The nucleic acid test is the new coronavirus antigen. The Chinese vaccine is an inactivated vaccine. It is a “killed” pathogenic microorganism. It has completely lost its infectivity and replication ability. Therefore, it will not cause COVID-19 pneumonia after vaccination, nor will it The new coronavirus nucleic acid test was positive due to vaccination.

Do I still need a nucleic acid test after receiving the COVID-19 vaccine?

Vaccination can reduce the risk of infection to a certain extent, but the protective effect of any vaccine cannot reach 100%. If necessary, it should still cooperate with relevant departments to carry out nucleic acid testing.

Can an individual bring the COVID-19 vaccine to colleagues overseas for vaccination?

There are strict approval procedures for the entry and exit of the COVID-19 inactivated vaccine. Individuals are not allowed to carry the COVID-19 inactivated vaccine out of the country without authorization, otherwise, they may face the risk of violating Chinese or other coutnries’ laws.


(source:internet, reference only)

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