: Popular Science China
Produced by: He Junwei, Pasteur Institute, Shanghai, Chinese Academy of Sciences
Producer: Computer Network Information Center, Chinese Academy of Sciences
I still remember a few days before the Spring Festival in 2018, the article "Beijing middle-aged under the flu" just appeared in When the circle of friends came out, the screen was blown up. The author used more than 20,000 words to record the process of the 60-year-old father-in-law's rapid deterioration to death due to influenza in just 29 days. Intubation, ICU, and artificial lungs failed to save the life of the elderly.
The flu is deadly! ?
Let us re-understand the flu~
Human Influenza virus is divided into A (A), B (B), C (C) three types, is the pathogen of influenza.
Influenza A virus (InfluenzaAvirus), also known as influenza A virus, is the most mutated of . Generally, there are 500 hemagglutinin spikes and 100 neuraminidase spikes distributed on the surface of an influenza virus, and can cause a worldwide influenza pandemic. The antigenicity of in HA and NA in influenza A virus will change, which is the basis for distinguishing virus strain subtypes, which is what we often call HXNX.
Influenza B virus (InfluenzaBvirus), also known as influenza B virus, has low pathogenicity to humans and can cause local epidemics.
Influenza C virus (InfluenzaCvirus), also known as influenza C virus, only causes insignificant or mild upper respiratory tract infection in humans and rarely causes epidemics.
So, what kind of virus can cause death? The
influenza virus is actually very small, between 80 and 120 nanometers in diameter. For example, a hair is about 0.05 mm in diameter, and it is cut radially into 600 strands, each of which is about as thick as the diameter of a flu virus. is right, it is something that can only be captured by the naked eye when it is enlarged 1000 times. Although it is small, its "boundless mana" has caused a worldwide influenza pandemic many times.
Why is there a flu vaccine and so many people still got the flu in early 2018?
When it comes to vaccination, the first problem is the low vaccination rate of . Taking the 2016-2017 flu season as an example, the vaccination rate of adults in the United States is 43.3%, and the vaccination rate of children is 59.0%; while the current season of vaccine supply in China With less than 25 million doses, the overall vaccination rate is less than 1.8%, which is indeed relatively low.
Secondly, this year's flu vaccine protection is not good. The seasonal influenza vaccine currently used in my country is mainly influenza virus split vaccine. Before 2018, all influenza virus split vaccines produced in my country were trivalent influenza vaccines. However, trivalent vaccines sometimes suffer from incomplete coverage in preventing seasonal influenza outbreaks. For example, in the 2017-2018 seasonal influenza season, the components of seasonal influenza vaccine strains in my country include A H3N2, A H1N1 and a line of influenza B strain .
But in fact, influenza B virus includes two lines, which are called BV and BY for short. The northern hemisphere trivalent vaccine recommended by WHO this year contains BV components and does not contain BY components, so the protection against BY viruses is limited. And this winter, the influenza BY strain is the dominant strain in my country. On June 8, 2018, my country's State Food and Drug Administration approved the production registration application of the quadrivalent influenza virus split vaccine by related companies. In addition to the H1N1, H3N2, and BV viruses that contain ordinary trivalent influenza vaccines, it also contains BY type viruses. Viruses (which are primarily used to prevent influenza virus infection in people 3 years of age and older).
What kind of people are suitable for the flu vaccine? The
population is generally susceptible to influenza viruses, and those at high risk for complications from influenza should get the flu shot. Simply put old ( ≥ 60 years old ) young ( children less than 5 years old, especially children under 2 years old ) disease ( cardiovascular disease, chronic respiratory disease, liver and kidney insufficiency, blood disease, nervous system disease , neuromuscular dysfunction, metabolic disease (including diabetes) and other chronic diseases, people with immunosuppressive diseases or immunocompromised ) pregnant ( pregnant women or women planning to become pregnant during flu season ) people. In the latest 2018 version of the flu diagnosis and treatment plan, there is another group of people listed as high-risk groups for severe influenza: obese , that is, people with a body mass index (BMI) greater than 30.
Speaking of which, there are many kinds of flu vaccines on the market, how do you choose?
The currently commonly used seasonal influenza vaccines are divided into two categories, one is the inactivated vaccine , and the other is the live attenuated vaccine , of which the inactivated vaccines are mainly split vaccines. In addition, seasonal influenza vaccines under development also include virus-like particles (LPs) vaccines, cell culture influenza vaccines, etc. The main process of
split vaccine
: collects influenza virus - splits with splitting agent - removes nucleic acid and macromolecular protein - retains antigen components HA and NA protein - removes splitting agent and purifies. Advantages of : can effectively maintain the immunogenicity of influenza virus, and can also reduce the probability of adverse reactions after vaccination, with good safety. On the basis of split vaccine,
subunit vaccine
splits influenza virus membrane proteins HA and NA by selecting appropriate splitting agents and splitting conditions, and selects appropriate purification methods to obtain purified HA and NA proteins. Advantage: The subunit influenza vaccine has a very pure antigenic component and can be used in children. It has good immune effect and clinical safety, and can stimulate the body to produce corresponding antibodies after inoculation. live attenuated vaccine Compared with inactivated influenza vaccine, live attenuated influenza vaccine has many advantages, including avoiding pain caused by intramuscular injection, wider range of vaccinated population, better mucosal immunity, cellular immunity and sustained immunity. longer time etc.
Is it safe to get the flu shot and are there any side effects?
The flu shot is safe, but like other medical products, flu shots can have adverse effects. The adverse reactions of
split vaccine and subunit vaccine (both inactivated vaccines) mainly include headache, sweating, muscle pain, joint pain, high fever, feeling unwell, chills, fatigue, itching, urticaria or non-specific rash. In addition, local reactions such as redness, swelling, pain, skin bleeding, and induration may occur at the injection site. The above clinical adverse reactions do not require any treatment, and the symptoms usually subside naturally within 1 to 2 days. The adverse reactions of
live attenuated vaccine mainly include skeletal myalgia, exudative otitis media, etc. In addition, the application of cold-adapted attenuated vaccine in children aged 15 to 35 months tends to increase asthma, so it is not recommended for children under 3 years old Use by children.
my country's original trivalent influenza vaccine and the newly launched quadrivalent influenza vaccine are inactivated vaccines injected intramuscularly. There is no difference in safety between quadrivalent influenza vaccine and trivalent influenza vaccine, and there is no significant difference in safety between domestic influenza vaccine and imported influenza vaccine.
Trivalent and quadrivalent vaccine, which one should be vaccinated?
The influenza vaccines supplied by in my country in 2018-2019 are 3-valent inactivated vaccine and 4-valent inactivated vaccine . Compared with the 3-valent inactivated vaccine, the 4-valent inactivated vaccine strain adds a subtype of influenza B (ie, the BV component of the influenza B strain). This is also the main virus strain circulating in my country during the 2017-2018 influenza season.
3-valent vaccine and 4-valent vaccine can prevent influenza infection. There is no priority recommendation, and any influenza vaccine can be voluntarily vaccinated.
When should I get the flu shot?
Influenza virus is easy to mutate, and companies will use the influenza virus strains predicted by the World Health Organization (WHO) every yearAs a result, the influenza vaccine of the current year was produced. The influenza vaccine usually produces antibodies with a protective level after 2-4 weeks of inoculation, and the antibody titer begins to decay after 6-8 months. Therefore, it is recommended to vaccinate the influenza vaccine every year.
The time and duration of the peak flu activity in different regions vary each year. It is recommended that everyone get the flu vaccine as soon as possible after it is launched, preferably before the end of October. Of course, if not vaccinated before the end of October, it can also be vaccinated throughout the epidemic season.
Pregnant women can be vaccinated against influenza at any stage of pregnancy, and it is recommended that they be vaccinated as soon as the current year's influenza vaccine becomes available.
Can I still catch a cold after getting the flu shot?
Getting the flu shot is the most effective way to prevent the flu and can significantly reduce the risk of flu and serious complications for those who get the flu shot. In most years, influenza vaccines are well matched to circulating influenza strains and provide good protection. However, there is also a certain chance that the strain of influenza vaccine does not match the circulating strain, which in turn affects the protective effect of influenza vaccine.
has been vaccinated against influenza, which does not mean that you will no longer get colds. Influenza vaccines are only aimed at influenza, and will only produce antibodies against influenza viruses, but have no ability to prevent and resist colds caused by bacteria, other viruses or mycoplasma. Therefore, some people catch a cold after being vaccinated against the flu, thinking that the vaccine is ineffective, but it is not.
The flu vaccine is a concern of many parents. Is it safe to get the flu vaccine at school?
should be safe. If the influenza vaccine is transported and stored in the cold chain, and within the validity period, the body is in a healthy state at the time of immunization, there will generally be a corresponding immune response after vaccination. If the body produces a corresponding high titer of antibodies after immunization, it indicates that the vaccination is effective, but it does not mean that it can protect 100% of the possible influenza virus. Even if 100% protection is not guaranteed, symptoms will be somewhat relieved once you catch a cold.
said so much, then there is a chance to get a flu shot in front of you, do you take it or not?
