Liu Hua
Pediatrician at Beijing United Family Hospital
Master of Tianjin Medical University
Recently, there have been frequent consultations about the influenza vaccine. Beijing has just started to make an appointment for influenza vaccination. I also feel that everyone is significantly more enthusiastic than previous years for influenza vaccine vaccination. .
Today, I will talk about the flu vaccine. The following 16 questions are all the flu vaccine questions I can think of.
1. Why is it necessary to get the flu vaccine at
this year?
First, don't underestimate the flu. It is estimated that the seasonal epidemic of influenza causes 5-10% of adults and 20%-30% of children to get influenza every year, resulting in 3 million to 5 million severe cases and a large number of deaths. According to statistics, there are as many as 290-65 million people related to the respiratory tract caused by influenza each year.
Second, the key populations are especially in need of protection: pregnant women, infants, the elderly, and patients with chronic underlying diseases are at higher risk of severe complications and death after influenza than healthy adults.
Third, influenza vaccination is the most direct way to block the spread of influenza virus and prevent cross-infection. It is also the most economical, effective, safe and convenient preventive measure.
Fourth, the particularity of this year is that the global epidemic situation of the new crown epidemic continues unabated. There is no doubt that the country's prevention and control of the new crown virus will continue. During this special period of
, if fever, cough, and flu-like symptoms occur, corresponding isolation will inevitably be carried out, study and work will be interrupted, and corresponding screening will be carried out. Even family members may also need corresponding screening and possible temporary work interruption. Therefore, in this special period, there is more protection and less disturbance.
2. What is the current situation of influenza viruses?
The number of influenza tests in the world is still very small, and the current surveillance is dominated by influenza B viruses. In the mainland of my country, the influenza activity in the northern and southern provinces remains at an extremely low level, with only sporadic influenza detections (as of 2020 September 13). The positive rate of influenza testing in southern provinces was 0.1%; in northern provinces, no influenza virus was detected. Image source of
: China National Influenza Center
In European and American countries, influenza activity is also maintained at a low level. For example, the consultation rate of influenza-like cases in the United States remains at a low level of 1.0%, and is lower than the baseline level of 2.4%. The positive percentage of influenza virus testing is 0.15% (as of September 12, 2020); the positive percentage of positive influenza virus testing in Canada (0.03%) remains at the lowest level in the past nine influenza seasons; Europe also has 812 fixed-point surveillance samples. One sample tested positive for influenza virus (June 27 to August 23, 2020).
is still in the non-popular season around the world. Image source of
: US Centers for Disease Control and Prevention
3. How is the strain
identified in the flu vaccine?
The World Health Organization has a global influenza surveillance network, including five WHO influenza reference and research collaboration centers (WHOCC), namely:
US Centers for Disease Control (Atlanta, USA);
Francis Crick Institute, UK (London, UK) );
Victorian Infectious Disease Reference Laboratory (Melbourne, Australia);
Japan National Institute of Infectious Diseases (Japan, Tokyo);
China National Institute of Viral Disease Control and Prevention (China, Beijing).
At the same time, there are more than 100 central sites of influenza surveillance laboratories in more than 100 countries, which monitor influenza throughout the year, collect and test a large number of influenza virus samples from patients, and these laboratories send representative viruses to The five cooperating centers of WHO obtained a recommended virus strain for use as a vaccine by analyzing the sequence characteristics of the influenza virus and using some scientific methods. The
virus may come from a flu virus isolated from a patient, or it may be a fusion and isolated from different patientsThe sequence characteristics of the multiple virus strains obtained, this virus will be used as the standard vaccine strain for production.
WHO organizes two-yearly relevant discussions and analyses to make predictions and recommendations (the northern hemisphere meeting takes place in February and the southern hemisphere in September). The WHO recommends that specific vaccine virus programs be included in influenza vaccine preparation, but then each country They will decide for themselves which strains of vaccine should be included in the flu vaccine licensed in their country.
4. How long does it take to produce flu vaccine? The preparation of the
flu vaccine is not as simple as imagined. From the above mentioned vaccine prediction, to manufacturer production, clinical testing, and the process of being ready for use, it takes at least six months.
Therefore, in order to be able to produce enough vaccines in time, manufacturers may start planting one or more vaccine viruses before February. According to experts’ guesses on the possible epidemic of the virus, they decide to choose the most likely to be included in the vaccine. Vaccine influenza strain.
5. What is the flu virus strain?
influenza virus includes four types A, B, C, and D. The influenza viruses that infect humans are mainly type 3, namely A, B, and C. The influenza viruses that are prevalent and pathogenic are mainly types A, B, and C. The clinical symptoms are mild and type D does not infect humans. Therefore, we generally mention only A stream and B stream .
influenza virus model
Image source: US Centers for Disease Control and Prevention
As can be seen from the picture, there are two kinds of proteins on the surface of the virus, namely hemagglutinin (abbreviated as H) and neuraminidase (abbreviated as N) ), these proteins can bind to antibodies produced by the human body and are called antigens.
can be divided into different subtypes according to the different combinations of 18 kinds of hemagglutinin and 11 kinds of neuraminidase on the surface of influenza virus;
A stream can be divided into subtypes such as H1N1 and H3N2, while the second stream only has Yamagata The two lineages of line and Victoria line, line and subtype are understood as the same meaning. After
, according to different genes, it can be further divided into specific groups and subgroups, such as 6B.1 in the figure below. Image source of
: provided by the author:
When a new strain of influenza virus is isolated from the major laboratories of influenza, it will be named according to the location and time of discovery. The specific method is as follows:
Image source: provided by the author
It is worth mentioning that, Many people think that the trivalent and quadrivalent influenza vaccine strain information (XXX-like virus) recommended by the World Health Organization's Global Influenza Surveillance and Response System is the recommended "strain" for influenza vaccine.
But in fact, it can be understood that this is the team name of the four "teams". Each team has one or more team members, and these team members are the candidate strains for preparing vaccines. The isolated
of each strain The "place name" may be different from the place name in the "team name", and the name of the virus strain does not contain "like virus".
6. Who should get the flu vaccine?
is based on the safety and effectiveness of influenza vaccines, and the susceptibility characteristics of the entire population of influenza viruses. Therefore, except for individuals who are known to have severe allergic contraindications, all people over 6 months of age should receive influenza vaccine.
"Technical Guidelines for Influenza Vaccination in China (2020-2021)" focuses on several groups of people, and is the priority group recommended for influenza vaccination:
6 to 23 months old infants;
2 to 5 years old children;
under 6 months Family members and caregivers of babies;
people in key places (teachers and students in kindergartens, primary and secondary schools, detainees and staff of prison institutions, etc.);
medical staff;
elderly care institutions, long-term care institutions, welfare homes Vulnerable employees in places where people gather;
60 years old and aboveThe elderly at home;
patients with chronic diseases, including cardiovascular diseases (except simple hypertension), chronic respiratory diseases, liver and kidney dysfunction, blood diseases, neurological diseases, neuromuscular dysfunction, metabolic diseases (including diabetes), etc. ; Z4z
pregnant women or women preparing to become pregnant during the flu season.
7. Who can not get the flu vaccine?
People who are allergic to any components contained in the vaccine (including excipients, formaldehyde, lysing agents and antibiotics) are prohibited from vaccination.
Patients suffering from mild to moderate acute illness with or without fever are recommended to vaccinate after the symptoms subsided.
The domestically marketed vaccines this year are trivalent live attenuated influenza vaccine (LAIV3). If the patient has taken influenza antiviral drugs 48 hours before vaccination, children aged 2 to 4 years with asthma; those with weakened immune function, and those with immunization People with low functions who are in close contact, as well as pregnant women, children and adolescents treated with aspirin or drugs containing salicylic acid are prohibited from vaccinating this trivalent live attenuated influenza vaccine.
8. Can I get the flu vaccine if I am allergic to eggs?
The Pharmacopoeia of the People's Republic of China (2015 and 2020 editions) does not include those who are allergic to eggs as a contraindication for influenza vaccination. The
Pharmacopoeia stipulates that the ovalbumin content in the whole influenza virus inactivated vaccine should not be higher than 250 ng/dose, and the ovalbumin content in the split vaccine should not be higher than 200 ng/ml. The measurement of egg protein content in commonly used influenza vaccines in my country shows that the maximum content does not exceed 140 ng/ml.
Foreign studies on egg allergies vaccinated against influenza have shown that no serious allergic reactions have occurred. The U.S. Prevention Working Group has been recommending that people who are allergic to eggs also get the flu vaccine since 2016.
Therefore, egg allergy is not a contraindication to the flu vaccine.
9. When is the appropriate flu vaccine?
usually produces a protective level of antibodies after 2 to 4 weeks of influenza vaccination, and the antibody titer begins to decay after 6 to 8 months.
The time and duration of the annual peak of influenza activity in various parts of our country are different, but the supply of influenza vaccines varies from place to place. In order to ensure immunization protection before the flu season, it is recommended that as long as the flu vaccine is available, vaccination can be arranged as soon as possible. The guidelines suggest that it is best to complete the immunization before the end of October;
For those who have not been vaccinated before the end of October, the entire flu season It is recommended to vaccinate, even if the flu vaccine has not been vaccinated, even if the local flu is high. People who have completed the entire vaccination process in accordance with the vaccination procedures in the same influenza season do not need to repeat vaccination.
10. What kinds of flu vaccines are there?
my country's domestic batch of influenza vaccines are as follows:
➊ Trivalent inactivated influenza vaccines: including split vaccines (split influenza virus vaccines) and subunit vaccines (influenza virus subunit vaccines). There are two dosage forms, 0.25 mL is suitable for 6-35 months old infants and 0.5 mL is suitable for people ≥ 36 months old.
➋ Quadrivalent inactivated influenza vaccine (IIV4): Only split vaccine (tetravalent influenza virus split vaccine). There is only one dosage form of 0.5 mL, which can be used to vaccinate people ≥ 36 months of age.
➌ Trivalent live attenuated influenza vaccine (LAIV3): freeze-dried live attenuated influenza vaccine for nasal spray. For people aged 3 to 17 years. The live attenuated nasal spray influenza vaccine is vaccinated by nasal spray vaccination, which is given every year.
11. Is there a difference between trivalent and quadrivalent influenza vaccine? The
3-valent influenza vaccine refers to the Victoria line that includes the H1N1, H3N2 subtypes and the B virus in Type A. In addition to the above three serotypes, the 4-valent influenza vaccine also has an additional Yamagata line serotype. In terms of protection,
has no difference between trivalent and quadrivalent serotype vaccine components. The quadrivalent flu vaccine has more protection against Yamagata influenza.
Therefore, if you can choose the flu vaccine at the same timeIn this case, you can give priority to the 4-valent influenza vaccine. If there is only a trivalent influenza vaccine when the supply is short, it is not recommended to refuse a trivalent influenza vaccine in order to wait for the 4-valent influenza vaccine.
For children under 3 years old in China, there are only three-valent vaccines, and no four-valent vaccines.
12. How to get the flu vaccine?
The recommended vaccination procedures in the Technical Guidelines for Influenza Vaccination in China (2020-2021) are as follows:
➊ Children aged 6 to 8 years: Children aged 6 to 8 years who have received less than 2 doses of influenza vaccine for the first time should be vaccinated Two doses, with an interval of ≥ 4 weeks, the above principles are recommended for both IIV or LAIV; for children who have received two or more influenza vaccines in 2019-2020 or before, one dose is recommended.
➋ Children 9 years and older and adults: only 1 dose is required.
Picture source: Technical Guidelines for Influenza Vaccination in China (2020-2021 Edition)
However, in clinical practice, influenza vaccination procedures are more frequently implemented according to the instructions of a certain brand of influenza vaccine.
Such as the instructions for a certain brand of vaccine: children aged 6 to 35 months, the first dose is given 2 doses, with an interval of ≥ 4 weeks. If you have received at least 2 doses in the past, it is recommended that you only need 1 dose. Over the age of 36 months, you only need one dose regardless of whether you are vaccinated for the first time.
The instructions for the domestic flu vaccine suggest that children aged 6 to 35 months, whether the first dose or not, should be given 2 doses at an interval of ≥ 4 weeks (or 2 to 4 weeks), and one dose for those over 3 years old.
Therefore, for children over 3 years old, just like adults, only one dose of influenza vaccine is required; for children under 3 years old, follow the instructions for vaccination.
13. Will you get flu after vaccination?
Although the flu vaccine is the most effective way to prevent flu. However, the effectiveness of the flu vaccine is never 100% effective. Studies from the 1940s to the present often show that the effectiveness of influenza vaccines is basically 70% to 90% in the good years. In many cases, the effectiveness of the flu vaccine is less than 60%. In some years, the effectiveness of the vaccine even drops to 10%.
In this case, do we still need to get flu?
is of course necessary!
You need to know that in the influenza epidemic in Hong Kong in 2018, more than 300 people died from influenza according to statistics before May, and the overall death toll has caught up with the level of the SARS outbreak in Hong Kong in 2003.
WHO data shows that the seasonal epidemic of influenza causes 5-10% of adults and 20-30% of children to get influenza every year, resulting in 3 million-5 million severe cases and 250,000-500,000 deaths.
University of Minnesota epidemiologist Michael Osterholm said that considering the large number of deaths caused by the severe flu season, "even if only 10% to 60% protection is better than nothing."
So, don't underestimate the flu, it is not the "common cold". As mentioned above, even if the flu vaccine can provide 10% to 60% protection, it is better than nothing.
14. Is the flu vaccine this year the same as last year?
is different.
The World Health Organization held the 2020-2021 Northern Hemisphere Influenza Vaccine Components Meeting in Geneva, Switzerland from February 24 to 27, 2020. After analyzing the global influenza virus epidemiology, etiology and vaccine serology, the vaccine was announced on the 28th Components.
One influenza virus in Guangdong, China and Hong Kong, China was constructed as a vaccine strain by the WHO Influenza Reference and Research Cooperation Center and the WHO core supervision laboratory and was selected as a vaccine component.
It is worth noting that this year's quadrivalent influenza vaccine has replaced three strains, only retaining the similar strains of B / Phuket / 3073/2013 (Yamagata line). The trivalent influenza vaccine has all changed strains. The four recommended strains of
are from Guangdong Maoming (HINI), Hong Kong (H3N2), Washington (BV), Phuket (BY), including influenza subtypes or strains circulating globally.
15. Is influenza vaccination safe?
Which one is domestic or imported? The
inactivated flu vaccine is very safe. The common side effects of
are mainly local reactions (redness, swelling, induration, pain, burning sensation, etc.) at the inoculation site. A few may have systemic reactions (fever, headache, dizziness, drowsiness, fatigue, myalgia, etc.) within 6 to 12 hours. General discomfort, nausea, vomiting, abdominal pain, diarrhea, etc.).
is usually mild and disappears on its own within a few days. Severe reactions rarely occur.
Some rare but serious adverse conditions may also occur after influenza vaccination, such as Guillain-Barré syndrome (about 1 to 2 cases per 1 million vaccinated persons), and severe allergic reactions (per distribution About 9 cases out of 10 million doses of vaccine).
However, there is not necessarily a causal relationship between flu vaccination and these adverse conditions. Studies have shown that the risk of Guillain-Barré syndrome after influenza infection (17.20 cases per 1 million infected persons) is much higher than after influenza vaccination (1.03 cases per 1 million vaccinated persons) It is much higher, so this year's influenza guidelines in our country also clearly stated that GBS is not a contraindication for influenza vaccine. The
study shows that there is no difference in safety between quadrivalent and trivalent inactivated influenza vaccines, and there is no significant difference in safety between domestic and imported influenza vaccines.
16. What else can we do besides actively vaccinating
?
In the face of influenza, in addition to influenza vaccination, taking daily protective measures can also effectively reduce the infection and spread of influenza, including:
➊ pay attention to fostering good hygiene and personal hygiene for children;
start with the most basic personal hygiene and pay attention to life Behavior prevention, wash your hands frequently, rinse your mouth frequently, drink more water, clear your nose frequently, avoid the habit of picking your nose, and keep your mouth and nose clean.
➋ Home isolation;
Pay attention to the natural disinfection of indoor ventilation and air convection. Strengthen the awareness of home isolation, pay attention to home isolation (washing hands frequently, sharing meals, not sharing towels, etc.) after the family has flu-like symptoms. You should not bring illness to school or work to avoid cross-infection in the collective environment. Try not to visit people with flu at home. You can use telephone greetings. During flu season, take your children as little as possible or not to densely populated public places.
➌ Pay attention to strengthening exercise and keeping warm, ensuring adequate sleep and regular work and rest;
supervise children to do more outdoor sports, adhere to aerobic exercise, improve body resistance, increase or decrease clothes in time, especially when sweating, change dry clothes in time to avoid sudden cold heat. Maintaining adequate sleep and regular work and rest can maintain a good immune state.
➍ In autumn and winter, pay attention to balanced nutrition.
In winter, there are few outdoor activities, and the sunshine time is short, the skin light synthesis is less vitamin D, so it is recommended to supplement vitamin D 400-600 units per day in autumn and winter. To develop good eating habits, a balanced diet. Eat more fruits and vegetables.
Author's public number: Hua Shao popular science time
disseminates the latest and most authoritative evidence-based medicine to everyone
long press to identify the QR code on the right. Follow>>
Supervisor fanfan
typesetting baita
Introduction to the flu vaccine
Are you in your heart now?
tells everyone a good news. Dr. Dingxiang and Dingxiang’s mother
have jointly established a number of high-quality outpatient clinics.
"vaccine appointment platform"
provides
appointment services for multiple vaccines including flu vaccines. , After entering the appointment page, you can click "Registration of vaccination requirements" , we will find the flu vaccine for you as soon as possible.
References
1. Technical guidelines for influenza vaccination in ChinaSouth (2020-2021)
2. WHO:
https://www.who.int/influenza/vaccines/virus/recommendations/2021_south/en/
3. Hong Kong Department of Health Epidemic Express:
https://www.chp.gov. hk/files/pdf/fluexpress_week38_24_9_2020_eng.pdf
4. U.S. CDC Epidemic Weekly Report: https://www.cdc.gov/flu/weekly/index.htm
5. U.S. CDC|Types of influenza viruses: https://www.cdc.gov/ flu/about/viruses/types.htm
6. China National Influenza Center>Influenza weekly report:
http://www.chinaivdc.cn/cnic/zyzx/lgzb/202009/t20200919_219246.htm
7. For development and production in the northern hemisphere 2020-2021 Candidate vaccine strains and efficacy test reagents for influenza season vaccine: https://www.who.int/influenza/vaccines/virus/candidates_reagents/2020_21_north/en/
