How to get the flu vaccine this year? All your questions are here

As the hot summer passes and the weather gets cooler, more and more inquiries about flu vaccines are being received online and offline.

Many parents are overwhelmed by the variety of flu vaccines on clinic posters, appointment forms or mobile phones - what are the differences? Which one can the child get? Do the whole family need to get it?

Let’s answer these questions one by one today.

What types of influenza vaccines are available in mainland my country this year?

A: From a technical point of view, there will be three types of influenza vaccines this year:

① Influenza inactivated (split) vaccine (trivalent/quadrivalent, injection)

② Inactivated influenza (subunit) vaccine (trivalent/quadrivalent, injection)

③ Live attenuated influenza vaccine (trivalent, nasal spray)

Among them, infants and young children aged 6 months to 3 years can only be vaccinated with ① inactivated influenza (lysate) vaccine; adults over 18 years old can be vaccinated with ① inactivated influenza (lysate) vaccine and ② inactivated influenza (subunit) vaccine; and children and adolescents aged 3 to 17 years old can be vaccinated with all three of the above influenza vaccines.

(Specific vaccine supply is subject to local actual conditions)

Split, subunit and live attenuated vaccines

What do they all mean?

Answer: Both “split” and “subunit” vaccines are “inactivated” vaccines (commonly known as “dead vaccines”), and do not contain live viruses.

1

Influenza “split” vaccine

The vaccine does not contain the "whole body" of the virus, but the virus is "dismembered", filtered, purified, and made into a vaccine, which can reduce adverse reactions. Currently, most brands of inactivated influenza vaccines are "split" vaccines.

2

Influenza “subunit” vaccines

It has one more process than the "lysis" vaccine, which further removes the internal proteins of the virus and extracts only the HA (neuraminidase) and NA (hemagglutinin) components. It has higher purity, fewer impurities, and is theoretically safer, and the effect is no weaker than the "lysis" vaccine.

3

Live attenuated influenza vaccine

The live attenuated influenza vaccine simulates the natural infection of the influenza virus . The weakened virus that cannot cause disease is sprayed into the nasal cavity, which can produce mucosal immunity, humoral immunity and cellular immunity.

What do “trivalent” and “quadrivalent” mean? Which one should I choose?

Answer: The "valent" in vaccine (note that it is not "media" or "order") refers to the number of types of pathogens that the vaccine can prevent - such as 4-valent meningococcal conjugate vaccine, 9-valent HPV vaccine, 13-valent pneumococcal conjugate vaccine, etc.

In terms of quantity, the quadrivalent influenza vaccine can prevent one more subtype of influenza virus than the trivalent one.

However, since March 2020, the Global Influenza Surveillance Network has no longer detected the "B/Yamagata" strain (the one that is additional to the trivalent strain in the quadrivalent strain).

Therefore, the World Health Organization believes that the current flu vaccine no longer needs to contain this ingredient . In this year (2024/2025 flu season), the United States will also only use trivalent flu vaccines.

In short, the trivalent vaccine is enough; if there is only the quadrivalent vaccine, of course you can get it.

After all, the World Health Organization cannot currently confirm that the B/Yamagata influenza virus is "extinct" and needs to "continue monitoring."

Due to various reasons, the "quadrivalent" influenza vaccine may be more abundant in mainland China. You don't have to insist on "only taking the trivalent" or "only taking the quadrivalent", just take whatever is available.

With so many types of flu vaccines, which one is the best?

Answer: The "Technical Guidelines for Influenza Vaccine Immunization in China" states: For people who can be vaccinated with different types of vaccines from different manufacturers, "you can voluntarily receive any type of influenza vaccine, and there is no priority recommendation."

Therefore, as long as the vaccine is produced using the same process, there is no essential difference between brands.

Specifically (emphasis! To be tested!):

If you want protection that develops quickly, lasts longer, and is less painful , you can choose a nasal spray of the live attenuated influenza vaccine.

If you want to have fewer adverse reactions and have money available , you can choose inactivated influenza (subunit) vaccine.

If you are looking for good quality, low price and high cost-effectiveness , it is better to get the inactivated (split) influenza vaccine.

A brand of flu vaccine was recalled

What should we do with those who have been beaten?

Answer: Recently, a certain brand of influenza vaccine decided to proactively suspend the supply and use of the 2024-2025 influenza season because it monitored that the "potency" of the vaccine (which can reflect the protective effect of the vaccine) was showing a downward trend, and the use was suspended as a precautionary measure.

Please note that the manufacturer has only found a downward trend, not that it has become ineffective or deteriorated, and there are no safety issues. Those who have already been vaccinated do not need to worry or get a booster shot. Those who have not received or are about to receive the second shot can switch to a different brand.

When is the best time to get a flu shot?

A: Generally speaking, you can get the vaccine as soon as it is available locally. September and October are usually good times to get the flu vaccine. The CDC recommends that everyone should get the flu vaccine by the end of October.

Even if you don't get the vaccine before the end of October, you can still get it throughout the flu season. Pregnant women and some babies who need two flu shots are recommended to get vaccinated a little earlier.

Got the flu shot now

Will there be no protection by the beginning of next year?

A: No. The protective efficacy of inactivated influenza vaccine generally begins to decline after 6 months; however, children still have a certain protective effect after 12 months of vaccination with live attenuated influenza vaccine.

As long as it is administered in a timely and standardized manner, any flu vaccine can provide protection throughout the flu season.

The child is under 3 years old

Have received 2 flu shots before?

Why do some doctors say that 2 injections are needed?

Some only require 1 needle?

A: If the vaccinating physician administers the flu vaccine according to national guidelines, then:

(1) 6 months to 8 years old: 2 doses of influenza vaccine are required for the first time, with an interval of ≥ 4 weeks; if the vaccine has been given before, only 1 dose is required;

(2) Children 9 years and above and adults: 1 dose per year.

(3) However, if the vaccinating physician follows the procedures in the instructions for a specific brand of influenza vaccine, the following requirements may be given: 6 months to 3 years old: 2 doses per year, with an interval of ≥ 4 weeks; over 3 years old: 1 dose per year.

Both options are acceptable.

My child just got the 13-valent pneumonia vaccine yesterday.

Can I get a flu shot tomorrow?

Answer: According to the instructions, the nasal spray live attenuated influenza vaccine needs to be administered at least 1 month apart from another live attenuated vaccine (such as measles, mumps and rubella vaccine, varicella vaccine, live attenuated Japanese encephalitis vaccine, etc.).

Scientifically, since the injected inactivated influenza (split/subunit) vaccine is a "dead vaccine", it can be administered at the same time as any other vaccine, or at any time interval without affecting each other.

My baby is allergic to eggs/milk

Can I get a flu shot?

Answer: Yes.

In the 2015 and later editions of the Pharmacopoeia of the People's Republic of China, "egg allergy" is no longer a contraindication to influenza vaccination. ** Milk allergy is not a contraindication to vaccination. ** Before vaccination, there is no need to confirm whether you are allergic to a certain food.

The pharmacopoeia stipulates that the ovalbumin content in influenza vaccines should not exceed 500 ng/ml (exceeding this value may cause allergic reactions). With the improvement of production technology, the current maximum ovalbumin content in influenza vaccines does not exceed 140 ng/ml[7].

Studies have found that people who are allergic to eggs did not experience severe allergic reactions after receiving inactivated influenza vaccines and live attenuated influenza vaccines. If the instructions for a certain influenza vaccine list "egg allergy" as a contraindication, just switch to another brand.

My baby has a cold, can he get a flu shot?

Answer: It depends.

If you only have mild cold symptoms, such as occasional cough, runny nose, nasal congestion, mild diarrhea and fever (fever here refers to fever without obvious discomfort), eat, sleep and activities are normal, and there are no other discomfort symptoms, then you can get the flu vaccine normally.

The flu vaccine is not recommended for people who have had an acute, severe allergic reaction to the flu vaccine in the past.

My baby got the flu vaccine last December.

It’s not even a year yet, can I still play?

A: Yes. The composition of the flu vaccine is adjusted every year, and it is recommended to be vaccinated every year.

The "year" here refers to the "flu season that spans a natural year" - in September, December 2023 and even March 2024, the vaccine for the "2023/2024 flu season" will be administered; and from September 2024 to March 2025, the vaccine for the "2024/2025 flu season" will be administered . The interval between the two does not need to be greater than one full year.

Why I got a flu shot last year

Or do you have a fever or cough?

Answer: First of all, the protective efficacy of the influenza vaccine is not 100%, and it cannot guarantee that you will not get sick after getting the vaccine, but it can significantly reduce the risk of illness, severe illness, death, and complications.

Secondly, the incubation period of influenza is usually 1 to 4 days, and it usually takes 2-4 weeks (inactivated) or 3-5 days (attenuated) after vaccination to produce antibodies. If you have been infected with the virus before this, you will indeed "get the flu even after getting the vaccine."

In addition, the symptoms of many diseases (such as the common cold, whooping cough, mycoplasma pneumonia, adenovirus infection, etc.) have certain similarities (all may include fever, runny nose and cough), and the influenza vaccine cannot prevent these diseases.

Finally, if only a few people in a family, office, factory, school, or class get the flu vaccine, then an immune barrier for the population cannot be formed, the virus will continue to spread, and individuals will not be able to "stay immune."

Who needs to get the flu vaccine?

Answer: If there are no contraindications to vaccination, it is recommended that all people aged ≥6 months receive influenza vaccination every year.

The following groups are recommended for vaccination first:

(1) Medical personnel. Including clinical personnel, public health personnel and health quarantine personnel;

(2) Participants and support staff of large-scale events;

(3) Vulnerable people and employees in places where people gather, such as nursing homes, long-term care institutions, and welfare homes;

(4) People in key places, such as teachers and students in childcare institutions, primary and secondary schools, and prison and detention center personnel;

(5) Other high-risk groups, such as people aged 60 years and above, children aged 6 months to 5 years, patients with chronic diseases, family members and caregivers of infants under 6 months old, and pregnant women or women who are planning to become pregnant during the influenza season.

The baby has received the pentavalent vaccine

It contains the ingredient "Haemophilus influenzae type b"

Do I no longer need to get a flu shot?

Answer: We still have to fight!

Although the word "influenza" is included in its name, the "Haemophilus influenzae type b vaccine (Hib)" (or the pentavalent vaccine or quadrivalent vaccine containing this ingredient) prevents invasive diseases caused by the bacteria "Haemophilus influenzae type b" , such as pneumonia, meningitis, epiglottitis, bacteremia, etc., but cannot prevent influenza.

To prevent influenza virus infection, it is still necessary to get the influenza vaccine as early as possible.

How do I know I'm calling

This year's "new" flu vaccine

Or is it the “old” flu vaccine from last year?

A: The World Health Organization announced the recommended strains for this year's northern hemisphere influenza vaccine in February 2024. Compared with last year, only one component of influenza A (H3N2) has changed:

Generally speaking, influenza vaccines with a production date after April this year can be guaranteed to be "new vaccines".

To be on the safe side, you can check the strain type on the vaccine packaging box/instructions before vaccination, or consult the vaccinating doctor directly to see if it is from this year or last year.

References

[1] Yang Xiaoming, Gao Fu, Yu Yongxin, et al. Contemporary New Vaccines[M]. Beijing: Higher Education Press, 2020

[2]Wang Y, Zhang Y, Wu H, et al. Safety and immunogenicity of a quadrivalent

inactivated subunit non-adjuvanted influenza vaccine: A randomized, double-blind,

active-controlled phase 1 clinical trial [J]. Vaccine, 2021, 39(29): 3871-8.

DOI:10.1016/j.vaccine.2021.05.070.

[3]Barría Maria Ines, Luis GJ, Cheryl S,et al.Localized mucosal response to intranasal live attenuated influenza vaccine in adults.[J].Journal of Infectious Diseases, 2013(1):115-124.DOI:10.1093/infdis/jis641.

[4]https://www.who.int/publications/m/item/recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2024-2025-northern-hemisphere-influenza-season

[5]https://www.cdc.gov/flu/prevent/trivalent.htm

[6]https://cdn.who.int/media/docs/default-source/influenza/who-influenza-recommendations/vcm-northern-hemisphere-recommendation-2023-2024/202302_qanda_recommendation.pdf?sfvrsn=4f30952b_1

[7] Chinese Center for Disease Control and Prevention. Technical Guidelines for Influenza Vaccination in China (2023-2024)

[8]https://mp.weixin.qq.com/s/y-B8e5GLJ2hn3cgsD_y5dg

[9]https://www.cdc.gov/flu/prevent/vaccinations.htm#when

[10]Turner PJ, Southern J, Andrews NJ, et al. Safety of live attenuated influenza

vaccine in young people with egg allergy: multicentre prospective cohort study [J].

BMJ, 2015, 351: h6291. DOI:10.1136/bmj.h6291.

[11]https://www.who.int/zh/news/item/23-02-2024-recommendations-announced-for-influenza-vaccine-composition-for-the-2024-2025-northern-hemisphere-influenza-season

Planning and production

Source: Health Express (ID: D- HealthExpress)

Author: Ms. Wang from the Vaccine Department, Master of Public Health from Fudan University, former deputy chief physician of the Centers for Disease Control and Prevention

Editor: Yang Yaping

Proofread by Xu Lai and Lin Lin