CDC Study Points to Potential Benefits of Newer Flu Vaccines (2024)

January 31, 2024 – A recent CDC study suggests that vaccination with non-egg-based flu vaccines might improve the antibody response to circulating flu viruses over that of traditional egg-based vaccines, which are the most common flu vaccines worldwide. The study looked at people’s immune response to various flu vaccines to determine which vaccines induced the best antibody response to circulating influenza viruses. The findings of this study have potential implications for flu vaccination strategy and are part of an ongoing effort to develop better flu vaccines and use existing flu vaccines to maximum effect.

For more than 70 years, most influenza (flu) vaccines have been produced by growing influenza viruses in chicken eggs. One drawback of this production method is that it often introduces changes to the viruses as they adapt to grow in eggs. These so-called “egg-adapted changes” can render the vaccine viruses significantly different from circulating “wild” flu viruses. As a result, egg-based vaccines can prompt a person’s immune system to direct antibodies at targets, or “epitopes,” on the vaccine viruses that are not found on circulating viruses. This could result in reduced vaccine effectiveness (VE). Moreover, as CDC research has shown, this antibody response could be reinforced by repeated egg-based vaccination, which could contribute to further reductions in VE over time.

Now, a CDC study published in January in Nature Communications reports that multiple seasons of being vaccinated with non-egg-based flu vaccines may help refocus people’s vaccine-induced immune responses to better target circulating influenza viruses. Two non-egg-based flu vaccines—the recombinant flu vaccine and the cell culture-basedflu vaccine—were introduced in the United States during the 2013-14 flu season. The study, which looked at data from a randomized clinical trial conducted during the 2018-2019 and 2019-2020 influenza seasons, compared antibody responses following vaccination with recombinant, cell culture-based, or standard egg-based influenza vaccines among 1,400 people.

The results indicate that vaccination with recombinant influenza vaccine induced the most robust antibody responses against multiple vaccine viruses. They also indicate that repeated vaccination with non-egg-based flu vaccines could overcome the effect of prior repeated vaccination with egg-based vaccines. Redirecting the antibody responses away from egg-adapted epitopes resulted in higher antibody responses to cell-grown viruses that better represent circulating viruses.

The findings could inform decision-making related to optimal vaccination strategies for people in different age groups and populations.

For one, vaccination with non-egg-based flu vaccines could be especially beneficial for people who have been repeatedly vaccinated with egg-based vaccines. This could include health care personnel who have annual vaccination requirements and older adults, who tend to have been vaccinated more frequently than other groups of people. The study also adds to the evidence that when young children are first immunized against influenza (called being “primed”), they may benefit from getting a non-egg-based vaccine, as a person’s first exposure to influenza virus can play a role in shaping their immune response to subsequent influenza virus infection or flu vaccinations.

Currently, recombinant and cell-based flu vaccines are the only flu vaccines made without the use of eggs that are licensed for use in the United States. The flu viruses used in the cell-based vaccines are grown in cultured cells of mammalian origin. Recombinant flu vaccines do not require the use of a candidate vaccine virus (CVV) for production because they are created synthetically.

Some observational studies have shown greater protection against flu among people who received cell-based inactivated influenza vaccines compared with those who received standard-dose egg-based vaccines. Nevertheless, egg-based vaccines remain the most widely available flu vaccines and are an important preventive tool. The benefits of vaccination with any flu vaccine, including egg-based flu vaccine, still far outweigh the potential risks of not getting vaccinated. Currently CDC does not have a preference for the use of any one flu vaccine over another except among people 65 years and older. When available, CDC recommends people 65 years and older get a high-dose, an adjuvanted, or a recombinant flu vaccinebecause a review of existing studies suggested that, in this age group, these vaccines are potentially more effective than standard-dose unadjuvanted flu vaccines.

While vaccine effectiveness can vary, studies show that flu vaccination reduces the risk of flu illness by between 40% and 60% among the overall population during seasons when most circulating flu viruses are well-matched to those used to make flu vaccines. In people who get vaccinated but still get sick, flu vaccine has been shown to reduce severity of illness, taking flu from “Wild to Mild.” CDC estimatesthat during the 2022-2023 season, flu vaccination prevented about 6 million flu-related illnesses, 3 million medical visits, 65,000 hospitalizations, and 3,700 deaths. CDC recommends everyone 6 months and older get an annual flu vaccine.

If you have questions about which vaccine is best for you, talk to your doctor or other health care professional. More information on approved flu vaccines for the current flu season and age indications for each vaccine are available in CDC’s Table: U.S. Influenza Vaccine Products for the 2023-2024 Season.

CDC Study Points to Potential Benefits of Newer Flu Vaccines (2024)


CDC Study Points to Potential Benefits of Newer Flu Vaccines? ›

January 31, 2024 – A recent CDC study suggests that vaccination with non-egg-based flu vaccines might improve the antibody response to circulating flu viruses over that of traditional egg-based vaccines, which are the most common flu vaccines worldwide.

Why is it important for the CDC to update the flu vaccine? ›

Flu viruses are constantly changing, so flu vaccines may be updated from one season to the next to protect against the viruses that research suggests will be common during the upcoming flu season. Your protection from a flu vaccine declines over time.

What is the CDC advice on flu shots? ›

Everyone 6 months and older in the United States, with rare exception, should get an influenza (flu) vaccine every season. CDC's Advisory Committee on Immunization Practices has made this “universal” recommendation since the 2010-2011 influenza season.

Why do scientists need to make a new flu vaccine each year? ›

Because new strains appear frequently, the seasonal flu vaccine usually changes each year, as scientists determine how the virus has mutated and spread.

What are the positives of getting the flu vaccine? ›

The flu vaccine can lower your risk of getting the flu. It also can lower the risk of having serious illness from the flu and needing to stay in the hospital or dying from the flu.

Why do flu vaccines need to be updated? ›

Vaccination helps prevent the spread of influenza. Annual vaccination is required because influenza viruses are constantly evolving and the body's immune response to influenza vaccination may not persist beyond a year. A new vaccine is designed each year to target the changes in the circulating influenza viruses.

How long after a flu shot does Guillain-Barré develop? ›

Risk of GBS is maximum in the first 2–3 weeks post vaccination, but in most cases the estimated risk was one to two cases per million vaccinations.

What is a religious reason for not getting the flu shot? ›

According to Ruijs (16,17), Orthodox Protestant parents who refuse vaccination on religious grounds (17) claim that vaccination is an act of interfering with divine providence. Those who actually vaccinated their children consider the side-effects of vaccination as a God's sign that they made a wrong decision.

How effective is the flu shot in 2024? ›

March 1, 2024 -- The vaccines for this flu season are 41% to 44% effective in preventing flu-related hospitalization in adults and 52% to 61% effective for children, according to estimates in the CDC's Morbidity and Mortality Weekly Report issued Thursday.

What is the science behind the flu shot? ›

Recombinant Flu Vaccines

The HAs of an influenza virus are antigens. Antigens are features of the influenza virus that are recognized by the immune system and that trigger a protective immune response. Most flu vaccines are designed to trigger an immune response against the HAs of circulating influenza viruses.

Can you suggest why influenza vaccine HAs to be changed each year? ›

Genetic data: Flu viruses are constantly changing, and all flu viruses undergo genetic changes over time. A flu virus' genome consists of all the genetic information that makes up the virus.

Are flu vaccines still made in eggs? ›

To get the vaccines ready for humans, scientists alter the viruses so they can't cause the flu. The vaccines also are purified, meaning all but a trace amount of egg protein is removed. Because the egg proteins are removed, even if you are allergic to eggs, you can still get a flu shot.

What is the downside of a flu jab? ›

The most common side effects of the flu vaccine are mild and get better within 1 to 2 days. They can include: pain or soreness where the injection was given. a slightly raised temperature.

How long is the flu shot good for? ›

Yes, the flu shot wears off in about six months. The flu shot does not provide long-lasting protection, which is another reason we need to get one every year. When should I get a flu shot? We typically suggest getting the flu shot in the early fall, before the virus starts circulating in the community.

How long do flu antibodies last? ›

After about 6 months, your immunity starts to fade. This falling level of protection (from a lessening amount of antibodies), combined with ever-mutating flu viruses, means it's important to be vaccinated for the flu every year.

Why is it important to adapt vaccine against flu continuously? ›

Why do we need flu vaccinations every year? Flu viruses are constantly adapting and changing and as a result the immune response developed against a specific strain of flu may not always offer protection against a new strain. This means that last year's vaccine will not be effective against this year's flu.

Can you suggest why influenza vaccine has to be changed each year? ›

Genetic data: Flu viruses are constantly changing, and all flu viruses undergo genetic changes over time. A flu virus' genome consists of all the genetic information that makes up the virus.

How important is the flu vaccine this year? ›

Flu vaccination reduces the risk of flu illness, hospitalization, and death in addition to having been shown to have other important benefits. Likewise, getting a COVID-19 vaccine is the best protection against COVID-19, but those vaccines do not protect against flu.

What are some of the current challenges to production of the influenza vaccine? ›

The nature of the influenza virus as a constantly evolving pathogenic threat to humans via antigenic changes is a persistent problem that significantly interferes with current vaccination efforts. The two mechanisms altering the genetic composition of the virus are the antigenic drift and shift.


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