2023 edition of influenza vaccination handbook
Recently, a new strain has appeared in COVID-19.
According to the evaluation of the World Health Organization on August 9th, the mutant EG.5 shows the characteristics of enhanced transmission ability and immune escape ability.
If there is a peak in November in the future, it is very likely to form mixed infection with this year’s influenza virus.
The World Health Organization (WHO) has released the candidate strains of seasonal influenza vaccine in the northern hemisphere in 2023-2024, and our influenza vaccine has also arrived this year.
Components of tetravalent chicken embryo culture vaccine:
A/Victoria/4897/2022 (H1N1) PDM09-like virus
A/Darwin/9/2021 (H3N2)-like virus
B/Australia/1359417/2021 virus (B/Victoria pedigree)
B/Phuket/3073/2013-like virus (B/Yamagata lineage)
Tetravalent cell culture or recombinant protein vaccine components:
A/Wisconsin/67/2022(H1N1)pdm09-like virus
A/Darwin/6/2021 (H3N2)-like virus
B/Australia/1359417/2021 virus (B/Victoria pedigree)
B/Phuket/3073/2013-like virus (B/Yamagata lineage)
Components of trivalent chicken embryo culture vaccine:
A/Victoria/4897/2022 (H1N1) PDM09-like virus
A/Darwin/9/2021 (H3N2)-like virus
B/Australia/1359417/2021 virus (B/Victoria pedigree)
Trivalent cell culture or recombinant protein vaccine components:
A/Wisconsin/67/2022(H1N1)pdm09-like virus
A/Darwin/6/2021 (H3N2)-like virus
B/Australia/1359417/2021 virus (B/Victoria pedigree)
Now that the flu vaccine is in place, let’s talk about the flu virus and this year’s flu vaccine.
1. How terrible is the flu? Why do you suggest vaccination?
Influenza (influenza for short) is an acute respiratory infectious disease caused by influenza virus. It is spread by airborne droplets and people are generally susceptible, and influenza can kill people.
A considerable number of people don’t take the flu seriously, thinking that it is just a slightly worse cold.
In fact, the seasonal epidemic of influenza every year can lead to 3-5 million severe cases and 290,000-650,000 deaths worldwide. The annual influenza attack rate of adults in the world can reach 5%-10%, and that of children is as high as 20%.
This means that in the high season of influenza, one in every 10 adults is infected with influenza; One out of every five children will get the flu. And influenza will break out every 10-40 years, causing serious health and economic burden.
For example, in the United States, on average, 36,000 people die of influenza every year, which is more than deaths caused by alcohol or traffic accidents. As far as the United States is concerned, the annual economic losses caused directly or indirectly by the flu are as much as $7 billion.
In recent years, the incidence and mortality of influenza in China have shown a steep upward trend. According to the data of China Center for Disease Control and Prevention, in the first five months of 2019 alone, the number of reported cases of influenza reached 1.77 million, exceeding the total number of reported cases of influenza in the past four years.
In the past February and March of 2023, the positive rate of influenza virus detection exceeded 25.1%, forming a large-scale epidemic.
Vaccination against influenza every year is the most effective means to prevent influenza, which can significantly reduce the risk of influenza and serious complications. Therefore, WHO suggests that people should be vaccinated every year to prevent influenza and its complications.
However, in China, the importance of influenza vaccine has not been fully recognized by the whole society. Influenza vaccine is a self-funded "non-immunization program vaccine" with a low vaccination rate.
Second, how to vaccinate to prevent influenza virus more effectively?
1. Inoculate every year
Influenza virus is easy to mutate. In order to match the ever-changing influenza virus, the influenza vaccine recommended by the World Health Organization will update one or more strains in most seasons, and the vaccine strains are exactly the same as those in the previous epidemic season.
In order to ensure the maximum protection of the vaccinated population, even if the composition of influenza vaccine is exactly the same as that of the previous epidemic season, considering that the immunity of most vaccinators will gradually weaken over time, influenza vaccine still needs to be vaccinated every year.
2. Inoculate in advance
Clinically, the season in which influenza occurs most often varies according to different regions. In China, the annual cycle of influenza changes with the increase of the latitude of the earth. Generally, it is more prevalent in the northern provinces above 33 degrees north latitude, with the peak in January and February every year, and the southernmost provinces south of 27 degrees north latitude have the peak in April and June every year. In the mid-latitude areas between the two, there are two very obvious flu peaks every year.
Usually after 2-4 weeks of influenza vaccination, antibodies with protective level can be produced. Therefore, it is recommended to vaccinate the influenza vaccine 1-2 months before the peak of influenza epidemic every year, so as to effectively play the protective role of the vaccine.
3. Inoculation on demand
Besides trivalent and tetravalent influenza vaccines, there are also three types of influenza vaccines: children, adults and general vaccines, and even the vaccination methods are different. You can choose the most suitable seasonal influenza vaccine for vaccination according to your own situation.
Three, ten hot issues of influenza vaccine
1. How many shots should the flu vaccine take every year?
It depends on age:
Children and adults aged 9 and above:Only one dose is needed;
Children aged 6 months to 8 years:Children aged 6 months to 8 years who are vaccinated for the first time or have been vaccinated with influenza vaccine below 2 doses in the past should be vaccinated with 2 doses, with an interval of ≥4 weeks; Children who have been vaccinated with 2 or more doses of influenza vaccine before are recommended to be vaccinated with 1 dose.
2. Can I get the flu vaccine if I am allergic to eggs or milk?
In all authoritative documents and guidelines at home and abroad, people who are allergic to eggs are not considered as taboos for influenza vaccination.
In fact, if you are allergic to any food, you can get the flu vaccine normally. There is no need to confirm whether you are allergic to a certain food before vaccination. If you have allergic symptoms that require urgent medical intervention after eating eggs, such as anaphylactic shock, it is recommended to vaccinate in medical institutions that identify and manage serious allergic diseases.
3. Who really can’t get the flu vaccine?
Those who are allergic to the ingredients contained in the vaccine include excipients, formaldehyde, Triton X-100, etc. Other people with severe allergies; Those with a history of Guillain-Barre syndrome; Patients with uncontrolled epilepsy and other progressive neurological diseases.
In addition, critically ill patients with various diseases should be used with caution; Patients with acute fever, acute infection and acute attack of chronic diseases should be vaccinated after recovery. For different kinds of vaccines from different manufacturers, the vaccination contraindications listed in the instructions are slightly different. Please refer to the vaccine instructions for details.
Special attention should be paid to the contraindications of live attenuated influenza vaccine.(At present, only nasal spray influenza is an attenuated live vaccine listed in China):
① Persons with low immune function due to drug use, HIV infection and other reasons;
② Children and adolescents who have been treated with drugs containing aspirin or salicylic acid for a long time;
③ Children with asthma aged 2-4 years;
4 pregnant women;
⑤ Patients with Guillain-Barre syndrome (GBS) history;
⑥ Those who used antiviral drugs such as oseltamivir and zanamivir 48 hours before inoculation, or those who used palamivir 5 days before inoculation, or those who used balofloxacin 17 days before inoculation.
4. Will you still get the flu after the flu vaccine?
This is possible, because the virus circulating in some areas may not be the influenza virus contained in the vaccine. In addition, it should be noted that influenza vaccine can only prevent influenza, but not the common cold at the same time.
5. Is it necessary to have an interval of more than one year between influenza vaccination and last year’s influenza vaccination?
"Vaccination every year" does not mean that this year’s influenza vaccination time must be a whole year apart from last year’s. Accurately speaking, the "year" here refers to "every flu season that spans natural years".
The influenza vaccine of the current season will be listed before the epidemic season of that year, and it can usually be vaccinated in August and September, and the validity period will end in March of the following year. That is to say, the flu vaccine given in August and September of that year was the same batch as that given before March of the following year. The flu vaccine in August and September of the following year is the next epidemic season.
Then, if you were vaccinated in August and September of that year, you don’t need to be vaccinated in March of the following year. On the contrary, if you were vaccinated before March of the following year, you still need to be vaccinated in August and September of the following year. There is no saying that the interval must be one year, mainly depending on whether the vaccine you are vaccinated belongs to the season.
6. Can people who have had the flu within one year get the flu vaccine?
Having a history of influenza in the past is not a taboo for vaccination. In addition, influenza viruses are prone to mutation, so it is possible to prevent influenza viruses prevalent in the current season by vaccination. Therefore, vaccination is still needed.
7. Can I get a flu vaccine during pregnancy and lactation?
A large number of studies at home and abroad have confirmed that "pregnant women have a higher risk of severe illness, death and adverse pregnancy outcome after suffering from influenza", that is, if pregnant women are infected with influenza virus, it may bring serious harm to both the fetus and themselves.
Therefore, pregnant women should be vaccinated against influenza more than others. And pregnant women can be vaccinated with inactivated influenza vaccine at any stage of pregnancy. If you are pregnant or plan to be pregnant during the flu season, you should get the flu vaccine.
Under the premise of the instructions, lactating women can also be vaccinated with influenza vaccine, and they can breastfeed normally after vaccination.
8. What is the difference between different influenza vaccines?
At present, there are trivalent inactivated influenza vaccine (IIV3), tetravalent inactivated influenza vaccine (IIV4) and trivalent attenuated live vaccine (LAIV3) that have been approved for marketing, among which IIV3 includes split vaccine and subunit vaccine, and IIV4 is split vaccine, and attenuated vaccine is the nasal spray vaccine mentioned earlier.
The difference between inactivated vaccine and attenuated live vaccine is that the former does not contain active virus components while the latter contains attenuated virus components. They can all trigger the immune response of the human body.
In addition, at present, the inactivated and attenuated influenza vaccines listed in China are inoculated in different ways: the inactivated vaccine is intramuscular injection, and the attenuated live vaccine is intranasal spraying.
The difference between trivalent and tetravalent is that the latter has one more pedigree of influenza B than the former (which can be simply understood as preventing one more strain of influenza B virus), and there is no difference in the preventive effect of influenza A contained in the latter. All of them can be inoculated to prevent influenza, and there is no priority recommendation, that is, when the vaccine is available, whatever is used can be chosen voluntarily according to their own conditions.
9. There is a scheduling conflict between influenza vaccine and other vaccines. Which vaccines can be vaccinated at the same time?
Inactivated influenza vaccine, other inactivated vaccines and attenuated live vaccines, such as pneumococcal vaccine, live attenuated herpes zoster vaccine, varicella vaccine, measles vaccine and DTP vaccine, can be inoculated in different parts at the same time;
After vaccination with live attenuated influenza vaccine, other live attenuated influenza vaccines can only be vaccinated after an interval of more than 28 days;
Older people over 65 can be vaccinated with influenza vaccine and pneumococcal vaccine at the same time.
Other special provisions shall be subject to the vaccine instructions of specific manufacturers.
10. After taking antibiotics and antiviral drugs, how long will it take to get the flu vaccine?
There is no taboo to get flu vaccine after antibiotic use.
However, taking influenza antiviral drugs 48 hours before vaccination is not recommended (it can be vaccinated after 48 hours).
Although there are a few very small and low-quality literature reports that taking antibiotics may reduce the immune response of influenza vaccine, it is not clear whether this has clinical significance or not, and it has not yet become a consensus.
But then again, if you are taking medicine, the high probability is that you are unwell or even in the acute stage of the disease, then it is recommended to suspend vaccination. At least wait until the symptoms improve and the condition is stable, or consider vaccination after stopping taking medicine.
References:
[1]World Health Organization. Fact sheeton influenza(seasonal).In. [http://www.who.int/en/news-room/fact-sheets/detail/influenza-(seasonal)].
[2] Gong Zhenyu, Gong Xunliang. WHO’s recommendation on the composition of influenza vaccine virus strains used in the northern hemisphere during the influenza season from 2023 to 2024 [J]. Preventive Medicine, 2023,35 (05): 460. DOI: 10.19485/J.CNKI.ISSN 2096-5087.
[3] China Center for Disease Control and Prevention. The national epidemic situation of legal infectious diseases in .http://www.nhc.gov.cn/jkj/s2907/new_list.shtml? tdsourcetag=s_pcqq_aiomsgaccessed July,2019.
[4] Technical Guidelines for Influenza Vaccination in China (2022-2023).
[5] Liu Xiaoxue, Song Yifan, Zhang Zhaonan, et al. Analysis on the coverage of influenza vaccine estimation report in China in 2014-2021 [J]. China Journal of Viral Diseases, 2023,13 (03): 226-232. DOI: 10.16505/J.2095-0136.
[6]Hagan et al. Antibiotics-Driven Gut Microbiome PerturbationAlters Immunity to Vaccines in Humans. 2019, Cell 178, 1313–1328. full text：https://www.cell.com/cell/fulltext/S0092-8674(19)30898-0
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