May 24, 2022
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Editor’s Note: BBC Chinese recently launched the “You Ask and I Answer” column to facilitate more participation of readers and to make our topic selection and reports more suitable for the needs of the audience. We’ll add interactive windows to hot news or headlines where readers can contact us and submit questions.
In the third year of the new crown epidemic, Covid-19 is no longer an unfamiliar infectious disease. People’s understanding of it is deepening, and vaccine, drug development and epidemic prevention mechanisms are gradually advancing with the times. However, the virus continues to mutate. While the prevention and control restrictions are being lifted successively in most parts of the world, there are still some recurrences. There are still many unanswered questions about the new crown, vaccines, drugs and sequelae. Questions and answers are mentioned in the Q&A column.
The Covid-19 vaccine is one of the most-cited issues. We’ve compiled three of the most common questions to try to answer.
Q: What is the difference between vaccines developed and produced in China and other vaccines?
The main difference is the type of vaccine.
Inactivated vaccines use an intact, killed (inactivated) or modified copy of the virus so that it cannot replicate and thus not cause disease. It’s a well-established technology that is used in most vaccines against a variety of other diseases, such as hepatitis A and polio. Covaxin from Bharat Biotech of India is also an inactivated vaccine.
Another broad category of vaccines all contain some part of the virus, but with different techniques.
Vector vaccines, such as the CanSino vaccine, encapsulate the genetic material of the virus in another harmless virus that cannot replicate itself. After entering the human body, it instructs cells to make the new coronavirus spike protein. An adenovirus vector can be a common virus, such as a cold virus, that acts as a vector to bring the genetic code on the virus’s spike protein into a cell, like a Trojan horse. After the code enters human cells, it will guide the production of antibodies and memory cells, which can recognize and resist the real new coronavirus once it invades.
Janssen, Oxford/AstraZeneca and Novavax Covid-19 vaccines fall into this category.
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Vaccines contain the virus’s messenger ribonucleic acid (mRNA); this region is responsible for issuing instructions to make proteins. Nucleic acid vaccines work by sending instructions to host cells in the body to replicate the spike protein, but the immune system sees through the invader and produces antibodies to respond, and it has a memory that, once infected with the real virus, triggers the immune mechanism .
From the current known data, in general, the immune efficacy of nucleic acid vaccines is the highest among several different vaccines.
Q: Is it necessary to strengthen the needle? Can you mix and match?
Booster shots are necessary and can be mixed and matched, and many countries do it, for example the UK has three vaccines approved for use, Pfizer, Oxford/AstraZeneca and Moderna, but the third shot (booster) Basically, Pfizer and Modena are used, and Oxford/AstraZeneca can be used for special reasons, no matter which one was used in the previous two injections.
Many studies have shown that boosters can significantly improve the degree of immune protection, because the efficacy of vaccines will decrease over time. A booster shot after about half a year can not only improve the quality of antibodies, but also increase the number of antibodies in the blood.
Professor Charles Bangham, an immunologist at Imperial College London, explained: “You have more antibodies in your body, a higher concentration of antibodies in your blood, we don’t know how long that lasts, but the more vaccines you get , the longer the immune system’s memory lasts.”
After a booster shot, the immune system has the upper hand in the face of possible future mutant strains.
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Q: How often should I be vaccinated after infection? Do I still need a full dose of the vaccine after recovery?
The medical and health departments of different countries have different regulations on this. The UK has different regulations for different age groups: 12-17-year-old minors can only be vaccinated 12 weeks after infection with the new crown symptoms, mainly to avoid a very rare side effect – myocarditis. The recommendation for adults and people at high risk for Covid-19, including those over 12, is to get vaccinated 4 weeks after contracting Covid-19.
It is generally believed that an autoimmune response can provide protection for at least three months, or even six months, after a natural infection with the new coronavirus in young people without underlying medical conditions.
Experts recommend that even people who have been infected and recovered with autoantibodies should be vaccinated because natural immunity may be boosted and vaccines can provide a fair degree of immune protection against mutant strains. Antibodies produced from previous infections may not necessarily have strong immunity to different variants.
In addition to antibodies, immune protection has two other core components: virus-killing T lymphocytes and immune memory; only immune memory can activate the autoimmune system to automatically recognize and rapidly produce T lymphocytes, and antibody-producing B cells.
The study showed no decline in T cells and immune memory after vaccination.
A doctor’s opinion should be consulted as to whether a full dose is required.
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