Vaccine Info

Influenza Vaccines

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Last reviewed
June 18, 2021

Influenza vaccines, known as flu shots, protect people against the influenza viruses that research indicates will be most common during the upcoming flu season. Most importantly, influenza vaccines do not cause the seasonal flu since they are made with either killed or weakened viruses, says the U.S. CDC.

The most common flu shot in the Northern Hemisphere are quadrivalent vaccines that protect people against four viruses: influenza A (H1N1) virus, influenza A (H3N2) virus, and two influenza B viruses, said the CDC on August 21, 2020.

Influenza vaccine types are widely available: inactivated influenza vaccines (IIV) and live attenuated influenza vaccines (LAIV), says the WHO. Two new influenza vaccines have been licensed for use in people aged 65 and older; a quadrivalent high-dose influenza vaccine and a quadrivalent adjuvanted influenza vaccine.

The WHO, PAHO, EMA, and the US Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee published influenza vaccine composition recommendations for the 2021-2022 flu season. The detailed information is published on this webpage

Most people over 6-months of age are encouraged to get vaccinated every flu season since influenza infections can create severe consequences, said the CDC in 2010-11.

Quadrivalent Influenza Vaccines: 2021-2022 Flu Season

6 months and older:

Afluria is an inactivated quadrivalent influenza vaccine indicated for active immunization against influenza disease caused by influenza virus subtypes A and type B.

Fluarix is prepared from influenza viruses propagated in embryonated chicken eggs.

Flulaval is a quadrivalent, split-virion, inactivated influenza virus vaccine prepared from virus propagated in the allantoic cavity of embryonated hens’ eggs.

Fluzone Quadrivalent is an inactivated vaccine indicated for the prevention of influenza disease caused by influenza A subtype viruses and type B viruses

2-49 years of age:

FluMist is an Intranasal vaccine that is a live quadrivalent vaccine formulated to contain four vaccine virus strains.

Flucelvax is a cell culture-based flu vaccine to help offer protection against 4 flu virus strains 

18-64 years of age:

Flublok is made without the use of eggs. Therefore, it is not subject to the mutations that are sometimes introduced into the vaccine during egg adaptation that can cause the traditional vaccines to be ineffective.

65 years and older:

Fluad consists of an inactivated, quadrivalent influenza virus antigen produced in eggs and an oil-in-water emulsion adjuvant, MF59C.1.

Fluzone High-Dose contains 4 times the antigen of standard-dose inactivated influenza vaccines.

Trivalent Influenza Vaccine: 2021-2022 Flu Season

65 years and older:

Fluad consists of an inactivated, trivalent influenza virus antigen produced in eggs and an oil-in-water emulsion adjuvant, MF59C.1.

Influenza Vaccine Candidates

Existing flu vaccines contain weakened or inactivated influenza viruses with a mix of hemagglutinins (HAs), the proteins that stud their surfaces. These vaccines primarily aim to trigger antibody responses against HA’s top part or head. Genetic changes in flu viruses rarely alter most of the head. But a small amount of the head reassorts, or mutates, frequently, allowing new viral strains to dodge any immune memory and forcing flu vaccine makers to prepare new formulations each year, with updated HAs, wrote Jon Cohen, a staff writer for Science.

Flu-v Influenza Vaccine is a synthetic universal flu vaccine candidate that offers protection across a broad influenza spectrum forcing 1+NP forcing vaccine candidate consists of MVA, a replication-deficient pox viral vector safely tested in thousands of patients, to generate a strong immune reaction against Matrix 1 (M1) Nucleoprotein (NP) influenza antigens. 

NasoVAX is a recombinant intranasal vaccine that is being developed for both seasonal and pandemic use.

Redeeflu is a nasal vaccine candidate utilizing a proprietary M2 deleted, single replication influenza virus.

Zoonotic Influenza News 2021

Please visit the latest Avian and Swine Influenza News.

Influenza Vaccine News 2021

June 15, 2021 - The Journal of Experimental Medicine published a study led by Yale researchers that found common respiratory viruses jump-start the activity of interferon-stimulated genes, early-response molecules in the immune system, which can stop the SARS-CoV-2 virus replication within a person’s airway tissues infected with the common cold.

June 14, 2021 - The PAHO reported influenza B detections accounted for most of the meager numbers of influenza detections reported worldwide.

June 14, 2021 - Seqirus US and Novavax Inc. announced the first study to demonstrate the safety, immunogenicity, and efficacy profile of a COVID-19 vaccine candidate when co-administered with seasonal influenza vaccines. The data non-peer-reviewed is now available on medRxiv.

June 8, 2021 - The JAMA published a population-based cohort study with a mean follow-up duration of 3.6 years; maternal influenza vaccination during pregnancy was not significantly associated with an increased risk of adverse early childhood health outcomes.

June 4, 2021 - Nationwide, during week #21, the U.S. CDC reported 1.1% of patient visits reported through ILINet were due to Influenza-like Illness. This percentage is below the national baseline of 2.6%.

June 1, 2021 - The first doses of Seqirus’s enhanced influenza vaccine, destined for the U.K., come off a new high-speed fill-and-finish line in Liverpool, UK. Seqirus Liverpool is the largest vaccine manufacturing facility in the U.K., producing over 50m doses of seasonal influenza vaccine each year, with the ability to increase production to 200m doses in the event of an influenza pandemic.

May 28, 2021 - The U.S. CDC confirmed it performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses used for developing new influenza vaccines and to monitor evolutionary changes that continually occur in circulating influenza viruses. The CDC reported it antigenically characterized 9 influenza viruses collected in the United States from September 27, 2020, to May 22, 2021.

May 3, 2021 - Seqirus-US announced Phase 3 clinical data demonstrating that the company's cell-based quadrivalent seasonal influenza vaccine (QIVc) was as safe and immunogenic as a standard quadrivalent seasonal influenza vaccine (QIV) in children six months through <4 years of age during the U.S. 2019/20 influenza season.

April 29, 2021 - Peer-reviewed research: Efficacy of live attenuated and inactivated influenza vaccines among children in rural India: A 2-year, randomized, triple-blind, placebo-controlled trial. In this study, LAIV and IIV vaccines were safe and moderately efficacious against influenza virus infection among Indian children.

April 20, 2021 - Seqirus, part of CSL Limited (ASX: CSL), announced new real-world evidence on the company's MF59® adjuvanted, trivalent influenza vaccine (aTIV) peer-reviewed medical journal Clinical Infectious Diseases. Study results indicate aTIV was more effective in reducing influenza-related medical encounters than standard egg-based quadrivalent influenza vaccine and high-dose trivalent influenza vaccine among adults 65 and older during the 2017/18 and 2018/19 U.S. influenza seasons.

April 15, 2021 - Longeveron Inc. (NASDAQ: LGVN) announced today the completion of the Company’s Phase I/II clinical study of the use of Lomecel-B to improve immune response to influenza vaccine in subjects with Aging Frailty. Lomecel-B is an allogeneic, bone marrow-derived medicinal signaling cell (MSC) product manufactured under current good manufacturing practices (cGMP) by Longeveron. It is anticipated that the top-line trial results will be announced in the 3rd quarter of 2021. Lomecel-B can reduce inflammation associated with Aging Frailty and promote an anti-inflammatory state by releasing anti-inflammatory molecules, which can balance the immune system and improve the function of B lymphocytes. As B cells are responsible for antibody production in response to vaccines, Lomecel-B may boost antibody generation and immunity following vaccination in subjects with Aging Frailty.

March 30, 2021 - The European Medicines Agency issued recommendations for the influenza virus strains that vaccine manufacturers should include in vaccines to prevent seasonal influenza from autumn 2021.

March 27, 2021 - A study conducted in France published in The Lancet concluded 'Among patients admitted to hospital with community-acquired pneumonia who met clinical stability criteria, discontinuing β-lactam treatment after 3 days was non-inferior to 8 days of treatment. These findings could allow a substantial reduction of antibiotic consumption.'

March 24, 2021 - Researchers at the University of Washington School of Medicine announced they had developed experimental flu shots that protect animals from a wide variety of seasonal and pandemic influenza strains. If proven safe and effective, these next-generation influenza vaccines may replace current seasonal options by protecting against many more strains that current vaccines do not adequately cover. A study appears in the March 24 edition of the journal Nature.

March 19, 2021 - The Australian Technical Advisory Group on Immunisation released advice for immunization providers in its Statement on administering seasonal influenza vaccines in 2021. This year both flu and COVID-19 vaccines will be available in Australia. It is important to plan vaccination timing to give the best protection against both of these potentially serious diseases.

March 18, 2021 -  A paper published in the Journal of General Internal Medicine, physician-researchers at Beth Israel Deaconess Medical Center assessed the relative impact of COVID-19 on patients hospitalized with the viral infection in March and April 2020 versus patients hospitalized with influenza during the last five flu seasons at the medical center. Overall, the team demonstrated that COVID-19 cases resulted in significantly more weekly hospitalizations, more use of mechanical ventilation, and higher mortality rates than influenza.

March 8, 2021 - Certain patients have an increased risk of influenza infections and poor serologic response to standard influenza vaccination. A new study found tandem high-dose influenza vaccination leads to more robust and more durable seroprotection in high-risk patients.

March 4, 2021 - Seqirus announced that the U.S. Food and Drug Administration had approved FLUCELVAX® QUADRIVALENT, the company’s cell-based quadrivalent influenza vaccine, for an expanded age indication for people two years of age and older.

March 3, 2021 - RESEARCH ARTICLE INFLUENZA: Broad neutralization of H1 and H3 viruses by adjuvanted influenza HA stem vaccines in nonhuman primates. Antibodies elicited by these headless HA stabilized-stem vaccines neutralized diverse H1 and H3 influenza viruses. They shared a mode of recognition analogous to human bnAbs, suggesting that these vaccines have the potential to confer broadly protective immunity against diverse viruses responsible for seasonal and pandemic influenza infections in humans.

March 1, 2021 - PLOS reported 'the global burden of influenza-associated lower respiratory tract infections and hospitalizations among adults: A systematic review and meta-analysis. In this meta-analysis, the researchers estimated influenza viruses are associated with over 5 million hospitalizations worldwide per year. Together, the available data demonstrate the importance of influenza viruses as a cause of severe disease and hospitalizations in younger and older adults worldwide.'

February 26, 2021 - The WHO issued recommended composition of influenza virus vaccines for use in the 2021 - 2022 northern hemisphere influenza season.

February 26, 2021 - The National IHR Focal Point for the Russian Federation recently notified the WHO of avian influenza A(H5N8) in seven human clinical specimens. These are the first reported detection of avian influenza A(H5N8) in humans. According to the latest notifications from the World Organization for Animal Health, Afghanistan became the latest country to report highly pathogenic H5N8 avian influenza in poultry.

February 24, 2021 - Russian authorities reported the detection of influenza A(H5N8) virus infection in seven poultry workers in an outbreak of highly pathogenic avian influenza (HPAI) A(H5N8) virus on a poultry farm in the south of Russia. All seven human cases were reported to be mild or asymptomatic. HPAI A(H5N8) viruses circulated in European bird populations since 2014, causing large outbreaks and affected several million birds and poultry.

February 22, 2021 - MAJOR ARTICLE: Impact of the Influenza Vaccine on COVID-19 Infection Rates and Severity. The odds of testing positive for COVID-19 were reduced in patients who received an influenza vaccine compared to those who did not by 24%.

February 17, 2021 - Twice annually, the WHO organizes consultations with an advisory group of experts to analyze influenza virus surveillance data generated by the WHO Global Influenza Surveillance and Response System (GISRS) and issues recommendations on the composition of influenza vaccines for the following influenza season. These recommendations are used by the national vaccine regulatory agencies and the pharmaceutical companies to develop, produce and license influenza vaccines.

February 9, 2021 - Study published by The Lancet: Prevention of influenza during mismatched seasons in older adults with an MF59-adjuvanted quadrivalent influenza vaccine: a randomized, controlled, multicentre, phase 3 efficacy study. Summary: The prespecified criterion for showing the efficacy of aQIV in older adults was not met during the influenza seasons with high amounts of vaccine strain mismatch. Vaccine efficacy was higher against influenza cases associated with higher fever, representing a more clinically significant disease.

February 9, 2021 - The findings of a systematic review and meta-analysis published by The JAMA Network suggest that given the similarity in immunogenicity between the reduced dose intradermal and full dose intramuscular influenza vaccine, the low-dose intradermal vaccine could be a reasonable alternative to standard-dose intramuscular vaccination. It will be important to determine if this dose-sparing finding holds across age groups and newer vaccines, particularly when recent high-dose formulations have demonstrated improved immunogenicity in older adults in whom immune responses have historically struggled.

February 8, 2021 - GAVI article: How COVID-19 is altering cold and flu seasons. Pandemic restrictions and wider use of flu vaccines may have explained 2020’s record low cases of seasonal flu, but what will the picture look like in tropical countries with year-round flu?

February 3, 2021 - BioCryst Pharmaceuticals, Inc. announced that the U.S. Food and Drug Administration had approved a supplemental new drug application for RAPIVAB® (peramivir injection), expanding the patient population of RAPIVAB for the treatment of acute uncomplicated influenza to include patients six months and older who have been symptomatic for no more than two days. Before this FDA approval, RAPIVAB had been indicated for patients two years and older.

February 2, 2021 - Study: A replication-competent adenovirus-vectored influenza vaccine induces durable systemic and mucosal immunity. Intranasal influenza vaccine spurred strong immune response in the Phase 1 study and reported the U.S. NIH.

January 23, 2021 - Study: Clinical and Economic Outcomes Associated with Cell-Based Quadrivalent Influenza Vaccine vs. Standard-Dose Egg-Based Quadrivalent Influenza Vaccines during the 2018–19 Influenza Season in the United States. Among the overall cohort, QIVc had higher adjusted rVEs against hospitalizations/ER visits related to influenza, all-cause hospitalizations, and hospitalizations/ER visits associated with any respiratory event than QIVe-SD. The adjusted annualized all-cause total costs were higher for QIVe-SD compared to QIVc ((+$461); p < 0.05).

January 19, 2021 - Researchers observed decreased effectiveness of influenza vaccine with increasing time since vaccination for prevention of influenza A(H3N2), influenza A(H1N1)pdm09, and influenza B (Yamagata)-associated hospitalizations among adults. The maximum vaccine effectiveness (VE) was observed shortly after vaccination, followed by an absolute decline in VE of about 8 to 9% per month post-vaccination.

January 15, 2021 - The Massachusetts Department of Public Health is removing the vaccination requirement which applied to all children over the age of 6 months attending Massachusetts child care, pre-school, kindergarten, K-12, or college due to the “mild” flu season and the fledgling efforts to administer the COVID-19 vaccine.

January 14, 2021 - JAMA Network Original Investigation - Safety, Reactogenicity, and Health-Related Quality of Life After Trivalent Adjuvanted vs. Trivalent High-Dose Inactivated Influenza Vaccines in Older Adults. In a randomized clinical trial of 757 older adults (378 receiving aIIV3 and 379 receiving HD-IIV3), the proportion of participants with moderate-to-severe injection-site pain was not higher after aIIV3 than HD-IIV3. No vaccine-related serious adverse events occurred, and postvaccination health-related quality of life was similar between aIIV3 and IIV3-HD groups. These findings suggest that a safety standpoint, aIIV3 or HD-IIV3, is an acceptable option to prevent influenza in older adults.

January 12, 2021 - Over 80% of those aged 65 and over in England have received the flu vaccine so far this year, the highest uptake ever achieved, reported the NHS. Flu vaccine uptake rates are higher than last season for all other eligible groups. This includes an uptake rate of 51.5% in clinical at-risk groups (aged under 65 years), which is the highest achieved in the last seven seasons.

January 12, 2021 - JAMA Network article: Broad, Durable Antibody Response in Universal Flu Vaccine Trial.

January 9, 2021 - A study published in the International Journal of Infectious Diseases found early administration of Oseltamivir (Tamiflu) is associated with a reduction in 30-day readmissions and composite-outcome of 30-day readmissions and mortality in adult hospitalized influenza patients when compared to delayed/no-treatment.

Universal Influenza Vaccine Research

A key focus of influenza research programs is developing a universal flu vaccine that provides robust, long-lasting protection against multiple flu subtypes, rather than a select few. Such a vaccine would eliminate the need to update and administer the seasonal flu vaccine each year. It could protect against newly emerging flu strains, potentially including those that could cause a flu pandemic.

Influenza Medicines

Several medications, such as Tamiflu or Xofluza (Baloxavir Marboxil), can reduce the seasonal flu's severity and duration. Still, they're most effective in the first 48 hours after experiencing influenza symptoms. Access to these medicines requires a healthcare provider's prescription.

    Influenza FAQs

    Note: This page's content is aggregated from the US CDC, the WHO, pharmaceutical manufacturers, university studies, and the Precision Vaccinations news network. This content is reviewed by healthcare professionals, such as Dr. Robert Carlson.

    Clinical Trials

    No clinical trials found