Influenza vaccine

New CDC study shows flu vaccine prevented more than 7 million flu illnesses, 109,000 flu hospitalizations, and 8,000 flu deaths during the 2017-2018 flu season. 


Influenza viruses mutate each year and influenza vaccination is recommended every fall for all people age 6 months or older and less they’ve had a severe allergic reaction to influenza vaccination.

Ideally, the vaccine is provided before the end of October, but should be offered to all unvaccinated people throughout the influenza season.

Influenza vaccination rates declined by 6% in 2017-18 to only 37% in those 18 years and older.

Influenza vaccine effectiveness in 2017-2018 was 38%, and was estimated to have prevented 7.1 million ilnesses, 109,000 hospitalizations and 8000 deaths.


2020-2021 seasons inactivated influenza vaccine, given by intramuscular injection, will contain components of four different influenza viruses.

The inactivated influenza vaccines are approved for people age 6 months or older. 

Higher dose inactivated influenza vaccines are offered to people age 65 years or older.

Influenza is more severe in the elderly than in younger age groups, but influenza vaccines lack effectiveness in this older demographic due to a waning of the immune system with age.


A recombinant influenza vaccine manufactured without influenza viruses or eggs is available for people age 18 years or older. 

Live-attenuated influenza vaccine given as a nasal spray is approved for people with normally functioning immune system’s who are age 2-49 years old.

Recommended for health care workers to avoid transmitting infection to patients.

Influenza is unique among respiratory viral agents in that effective intervention to prevent transmission is present, that is vaccination.

Most effective means to protect susceptible individuals and decreasing viral transmission within a community.

Is administered to prevent individuals recipients from getting complications from influenza not, to control the spread of an epidemic throughout the community.

Cornerstone of prevention is annual vaccination.

Predominate influenza strains vary from year-to-year, affect the intensity and severity of the influenza season as well as the effectiveness of influenza vaccines.

When the vaccine and infecting viral agent are antigenically similar the vaccine prevents illness in 70-90% of healthy adults under the age of 65 years.

Least effective in those with the highest risk-young children, elderly and immunosuppressed individuals.

The antibody response and protection provided by the vaccine are lower among adults 65 years of age or older, than among younger adults.

A meta-analysis showed that influenza vaccine protection was 59% effective of the trivalent influenza vaccine in adults aged 18-65 and 83% of the live attenuated vaccines and children (Osterholm MT et al).

Trivalent influenza vaccines contain three antigens: 2 typeA lineage, usually H3N2  and each one two type B lineages Victoria or Yamagata.

Vaccination, although not it levels of other vaccines, provide some protection and may prevent complications such as pneumonia, hospitalization, and death and while patients may still develop influenza are likely to be at lower risk for associated complications.

Vaccination in oncology patients may result in less robust immune responses, but most patients have a moderate degree of immunologic protection developed against disease and should be utilized.

Administered to elderly patients with COPD decreases hospitalization rates by 52% for influenza and pneumonia and is associated with a 70% reduction in all-cause mortality.

Reduces related pulmonary infections, physician visits, hospitalizations and deaths among high risk individuals, decreases otitis media among children and absenteeism.

Prioritized populations include: children 6-23 months of age, ages 65 or older, pregnant women, nursing home and long-term facility dwellers, individuals aged 6 months to 18 years on aspirin therapy, healthcare workers with direct patient contact, household contacts of children 6 months of age or younger, patients aged 2-64 years with chronic medical conditions.

Maternal vaccination is associated with reduced risk of influenza virus infections and hospitalizations for newborns up to six months of age.

Recommended for routine vaccination of all children 6-59 months with trivalent inactivated influenza vaccine.

Pregnant women are at increased risk for complications from influenza.

It is recommended that all pregnant women be vaccinated with the trivalent during any trimester of pregnancy.

Maternal vaccination protects infants from influenza like illness during the first six months of life.

Trivalent inactivated vaccine is the primary method of vaccination for the majority at risk population.

Compared to standard dose vaccine, high-dose trivalent inactivated influenza vaccine (IIV3-HD)improves antibody responses to influenza among adults 65 years of age or older (DiazGranados CA et al).

High-dose trivalent inactivated influenza vaccine contains 4 times as much hemagglutinin as is contained in standard vaccines.


There are three types of influenza vaccines: inactivated, recombinant, and live-attenuated.

Two types of vaccine exist for seasonal influenza: one containing inactivated viruses and the other containing live attenuated viruses.

Both types of vaccines are trivalent.

Trivalent inactivated influenza vaccine is poorly immunogenic in young children, effective in only 59% in children older than two years.

Intranasal live attenuated influenza vaccine effective immunologically in 69-95.6% of children ages 2-7, but it cannot be used in children under two years of age because of increased hospitalization rate, or in children under age 5 with a history of wheezing, as it increases the risk of wheezing.

The three components of the vaccines are updated annually on the basis of national and international factors.

The influenza vaccine can protect for 6 months and last throughout the flu system.

Influenza protection up to 6 months is consistent for 91 to 180 days after vaccination among 60% of participants (Radin j).

During the 2017–2018 influenza season,vaccination was calculated to have prevented an estimated 7.1 million illnesses, 3.7 million medical visits, 109,000 hospitalizations, and 8,000 deaths.


After 189 days vaccine effectiveness decreases to 11%.

Efficacy of vaccines related to age, health, of the recipients and by extent of antigenic similarity between the strains included in the vaccines and those in the circulation months after.

Two distinct type B lines exist but only one can be included in the vaccines.

A study of inactivated and live attenuated vaccines that was randomized, double blind and placebo controlled given to healthy adults in the fall of 2007-2008: the inactivated vaccine was 50% more efficacious in preventing laboratory confirmed symptomatic influenza A, mainly H3N2, than the live virus (Monto).

Maternal immunization during pregnancy reduces influenza illness by 63% in infants up to 6 months of age and averts approximately one third of all febrile respiratory illnesses in mothers and young infants in A Bangladesh study (Zaman).

Antigenic drift in virus may occur after formulation of the year’s vaccine has taken place making the vaccine less protective.

Made from purified virions grown in hens’ eggs and are made to contain at least grams of the hemagglutinin of represented stains per 0.5 ml.

Live, attenuated influenza vaccine administered intranasally and approved for use among healthy persons 5-49 years of age who are not pregnant.

When administered to children in an intervention school: there was significant, but relatively modest, reductions in symptoms of respiratory illness and visits to physicians among households as compared to non-intervention schools, absenteeism from elementary and high school (but not middle school) was reduced associated was the number of paid workers days missed.

Currently influenza vaccine strategies have a small effect on mortality and morbidity in the end-stage renal disease population (McGrath LJ et al).

Live attenuated trivalent vaccine in young children is highly effective.

Live attenuated vaccine shows high efficacy when epidemic influenza viruses are not well matched to recommended vaccine antigens.

Affects metabolism of theophylline, but does not affect warfarin metabolism (Renton KW,Iorio A).

Inactivated vaccine are administered intramuscularly and approved for use in patients with high-risk conditions.

Comparison of the efficacies of inactivated and live attenuated vaccines reveals similar levels of efficacy.

Ohmit study of adults age 18-46 revealed 74% efficacy against culture confirmed type A (H3N2) influenza infections.

Quadravalent combination vaccine contains three times the amount of antigens included in the standard dose vaccine.

Quadravalent vaccine is produced without influenza virus or eggs and is approved in person is 18 years and older.

Quadravaent vaccine indices greater antibody response than ubadjuvanted standard dose vaccines and adults 50-64 years old.

Quadravaent vaccine 30% more effective than the standard dose in unajuvanted Quadravaent vaccine in preventing influence in adults 50 years or older in randomized controlled studies and more effective in those 50-64-year-old and more effective in those 65 years old and older.

Trivalent contains four times the amount of antigen and included in the standard does vaccine and is approved for persons 65 years and older, and induces greater antibody responses than unadvanted standard those vaccines in adults greater than 65 years.

Adjuvanted vaccine is trivalent and contains an oil in water emulsion of squalene that increases the immune response, it is approved for use in person is greater than 65 years old and induced a greater antibody response than unadjuvanted standard dose vaccines in adults more than 65 years

Flu vaccine 2018-2019 recommendations:

Vaccination against seasonal influenza is recommended for all individuals aged 6 months or older, including pregnant women.

Quadrivalent vaccines offer broader coverage against influenza B viruses, which primarily infect children.

The intranasal live-attenuated vaccine is recommended as an option.

Recombinant high dose and adjuvanted vaccines elicit greater antibody responses than standard dose unajuvanted vaccines are more effective among older patients in preventing influenza.

Flublok, a quadrivalent recumbent formulation has no egg protein and is an alternative for individuals age 18 or older who are allergic to eggs.

Flu Vaccine Recommendations for the 2019-2020 Season

The influenza vaccine should be offered by the end of October and continue to be offered as long is influenza circulating in the community.

In most adults, serum antibody levels peak about two weeks after vaccination.

Early vaccination may result in suboptimal immunity before the end of the influenza season, especially in older adults.

Children who require two doses should receive the first dose as early as possible so that second dose can be given by the end of October.

FluMist Quadrivalent, The intranasally administered live attenuated influenza vaccine is approved for use in healthy non-pregnant persons to-49 years old.

High does vaccine Fluzon High-dose Is an inactivated trivalent vaccine that contains four times the amount of antigen included in standard those influenza vaccine is approved for persons 65 years or older.


Randomized trials comparing standard dose influenza vaccine with high dose vaccine: high dose vaccine reduced symptomatic influenza.

Fluad is an adjuvant inactivated trivalent influenza vaccine for using individual 65 years and older.

Pregnant women should be vaccinated against influenza without regard to the trimester of pregnancy, but they should not receive the live attenuated vaccine.

The live attenuated influenza vaccine should not be used in immunocompromised persons.

Influenza can cause millions of illnesses, hundreds of thousands of hospitalizations, and tens of thousands of deaths worldwide each season.

Annual influenza vaccination offers important protection against influenza illness and its potential serious complications.

CDC and the Advisory Committee on Immunization Practices (ACIP) recommend routine annual influenza vaccination for all persons 6 months of age and older who do not have contraindications to vaccination.

CDC and ACIP recommend that vaccination be offered by the end of October.

Choices include inactivated, recombinant, or live attenuated influenza vaccines.

People 65 years of age and older may receive the trivalent influenza vaccine with adjuvant or the trivalent high-dose vaccine.

No preferential recommendation is made for one influenza vaccine type over another.

In patients with high-risk cardiovascular disease, high-dose trivalent inactivated influenza vaccine, compared with standard dose quadrivalent inactivated influenza vaccine, did not significantly reduce all cause mortality or cardiopulmonary hospitalizations.

Vaccination is particularly important for persons who are at increased risk for severe illness and complications from influenza.:

People who are immunocompromised

Pregnant and postpartum women

Children and adolescents (aged 6 months through 18 years)

Residents of nursing homes and other long-term care facilities

American Indians/Alaska Natives

People who are extremely obese

Healthcare personnel

Household contacts and caregivers of children under 5 years of age and adults 50 years of age and older

Household contacts and caregivers of persons with medical conditions that put them at increased risk for severe illness and complications from influenza.

Adverse effects: associated with Guillain Barre syndrome in about 1-2 cases per million persons vaccinated.

Soreness at the injection site is uncommon.

Most common adverse reactions are runny nose, nasal congestion, fever, sore throat, and soreness at the injection site.

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