Pre season talk about influenza vaccines: correct cognition without hesitation

Luwang, September 11th (Reporter Guan Xiaohui, Correspondent Li Chengxiu, Ma Jin) Influenza is an acute respiratory infectious disease caused by the influenza virus that poses a threat to human health. It is seasonal (commonly known as the "flu season") and can cause serious complications such as pneumonia, encephalitis, and even death in infants, young children, and the elderly. Therefore, outbreaks of COVID-19 are prone to occur in schools, kindergartens, and elderly care institutions. Although there was a nationwide outbreak of H1N1 influenza A from February to April this year, according to perennial epidemiological data in China, the southern and northern regions generally have a high incidence in winter and spring (November to February of the following year), and the areas south of the Yangtze River can also have a high incidence in summer. Therefore, we are currently in the pre flu season, which is the best time to receive influenza vaccines, especially for infants, young children, primary and secondary school students, the elderly, medical personnel, and entry-exit port staff. However, due to cognitive differences, some parents and vaccination populations have varying degrees of hesitation in vaccination, mostly suspecting the effective protection of the vaccine, followed by anxiety about vaccination safety. For this, let's talk about topics related to influenza vaccines together.

Cognitive misconception: still being infected after receiving the influenza vaccine and the theory of vaccine ineffectiveness

Before discussing this topic, let's first understand the relationship between preventing influenza virus infection and influenza vaccination. The ideal state is that after receiving the vaccine, our body produces protective antibodies to protect us from infection. The premise of this situation is that the antigen of the vaccine administered is exactly the same as that of the virus strain that infects us. When we receive widespread vaccination, we will form a group immunity that can eliminate this virus strain, such as the eradication of smallpox virus. However, in reality, this situation is very rare because the virus, in order to reproduce the species, constantly mutates to evade the neutralization and clearance of the human immune system (i.e., to evade the host's immune clearance through immune escape). As a result, we will still be infected after receiving vaccines containing previous strain antigens. For influenza viruses, in addition to mutation of the virus strain antigen, there is also a mechanism called "antigenic sin" to evade the clearance of specific neutralizing antibodies. The specific principle is that when we first infect a virus strain (such as H1N1), our immune memory cells will firmly remember the virus antigen, So, after receiving vaccines containing other viral antigens (such as H1N1, H3N2, and influenza B strain antigen vaccines) in the future, our body will still produce high levels of H1N1 antibodies, while the antibody levels of other strains are lower. As a result, if we re infect the H1N1 strain, we will be protected from infection. If we are infected with H3N2 or influenza B strain, we will still be infected (called off target), a process called immunoblotting in immunology, In fact, it is a protective mechanism that the virus has evolved through long-term struggle with its host.

Before discussing this topic, let's first understand the relationship between preventing influenza virus infection and influenza vaccination. The ideal state is that after receiving the vaccine, our body produces protective antibodies to protect us from infection. The premise of this situation is that the antigen of the vaccine administered is exactly the same as that of the virus strain that infects us. When we receive widespread vaccination, we will form a group immunity that can eliminate this virus strain, such as the eradication of smallpox virus. However, in reality, this situation is very rare because the virus, in order to reproduce the species, constantly mutates to evade the neutralization and clearance of the human immune system (i.e., to evade the host's immune clearance through immune escape). As a result, we will still be infected after receiving vaccines containing previous strain antigens. For influenza viruses, in addition to mutation of the virus strain antigen, there is also a mechanism called "antigenic sin" to evade the clearance of specific neutralizing antibodies. The specific principle is that when we first infect a virus strain (such as H1N1), our immune memory cells will firmly remember the virus antigen, So, after receiving vaccines containing other viral antigens (such as H1N1, H3N2, and influenza B strain antigen vaccines) in the future, our body will still produce high levels of H1N1 antibodies, while the antibody levels of other strains are lower. As a result, if we re infect the H1N1 strain, we will be protected from infection. If we are infected with H3N2 or influenza B strain, we will still be infected (called off target), a process called immunoblotting in immunology, In fact, it is a protective mechanism that the virus has evolved through long-term struggle with its host.

How to Choose a Vaccine after Correcting Cognitive Mistakes

Through the above discussion, we understand that after vaccination, in addition to inducing the production of protective antibodies to prevent infection, for people who may miss the target, the risk of severe illness and death can be reduced by training cellular immunity. After correcting our misconceptions from a cognitive perspective, how should we choose a vaccine?

Current vaccine formulations and target groups: The influenza vaccines currently used in China are divided into trivalent and tetravalent in terms of content and composition, with trivalent referring to the presence of H1N1, H3N2 influenza A and Victoria type B influenza antigens; Tetravalent refers to the presence of H1N1, H3N2 influenza A and Victoria and Yamagata influenza B antigens. At present, the vaccines listed in China are mainly as follows (specific target groups and vaccination methods are subject to the instructions)

(1) Trivalent influenza virus split vaccine (0.25ml): suitable for infants and young children aged 6 to 35 months, administered twice with an interval of ≥ 4 weeks, intramuscular injection. Children who were vaccinated last year only need to be vaccinated once this year.

(2) Trivalent influenza virus split vaccine (0.5ml): suitable for people over 3 years old, once vaccinated, intramuscular injection.

(3) Trivalent influenza virus subunit vaccine (0.5ml): suitable for people over 3 years old, administered once, intramuscular injection.

(4) Trivalent live attenuated influenza virus vaccine (0.2ml): suitable for people aged 3-17 years old, nasal spray, once.

(5) Tetravalent influenza virus split vaccine (0.25ml): suitable for infants and young children aged 6 to 35 months, administered twice with an interval of ≥ 4 weeks, intramuscular injection. Children who were vaccinated last year only need to be vaccinated once this year.

(6) Tetravalent influenza virus split vaccine (0.5ml): suitable for people over 6 months old, once administered, intramuscular injection.

(7) Tetravalent influenza virus subunit vaccine (0.5ml): suitable for people over 3 years old, administered once, intramuscular injection.

Timing and efficacy of influenza vaccination

Antibodies with protective levels can be produced 2-4 weeks after vaccination, lasting for about 6-9 months. According to the characteristics of the epidemic season in our northern region, it is recommended to complete the vaccination from September to October as the best time; Due to the aforementioned immune training effects after vaccination, vaccination is also effective during the epidemic season.

If the current epidemic strain is the same as the individual's first infection strain, vaccination can play a preventive role in infection. If it is not the individual's first infection strain, appropriate immune inflammatory reactions can also be regulated through immune training mechanisms, with common cold and mild pneumonia occurring more frequently, to protect individuals from the epidemic season safely.

In short, with the rapid development of vaccine science and technology, the accuracy and purity are becoming increasingly high, and the probability of adverse reactions is very low. I hope this article can elucidate the specific (protective antibodies → prevention of infection) and non-specific (regulating immune response → reducing severe illness and mortality) effects of influenza vaccines from a cognitive perspective, and protect us, especially infants, primary and secondary school students, and the elderly, from the flu season safely. It is hoped that this article can change our hesitant and anxious attitude towards influenza vaccination, and try to complete kindergartens, primary and secondary schools as much as possible by the end of October Influenza vaccination for elderly care institutions, hospitals, and populations at entry and exit ports.

Translated from: Lu Net Headline: Dongfang Information