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1. Inactivated Seasonal
Influenza Vaccines
By
Dr. Ashraf El-Adawy
Consultant Chest Physcian
TB TEAM Expert - WHO

2. Inactivated Seasonal Influenza Vaccine
(Flu Shot)
Q. What is flu ?
 Seasonal influenza, or ‘the flu’ as it is often called, is an acute viral infection
that mainly affects the respiratory system, caused by an influenza virus.
 The influenza virus is an orthomyxovirus that is classified antigenically as type
A, B and C.
 Type A influenza viruses are further classified into subtypes according to two
kinds of proteins on its surface : haemagglutinin (H) and neuraminidase (N).
 Among the many subtypes of type A viruses, influenza A (H1N1) and A (H3N2)
subtypes circulate among humans as a seasonal Influenza strains.
 Type B influenza virus is not categorised into subtypes, but lineages. There are
two influenza B lineages which circulate, Yamagata and Victoria, and these can
be further broken down into different strains.
 Human influenza A and B viruses can cause seasonal influenza epidemics.
 Influenza caused by type C virus occurs much less frequently than types A and
B and are not thought to cause seasonal epidemics ,that is why only influenza
A and B viruses are included in seasonal influenza vaccines.
Q. Is flu serious?
 Seasonal influenza is a serious public health problem, it has been estimated
that in developed countries, annual influenza epidemics infect about 10–20% of
the population each season.
 Worldwide, annual influenza epidemics are estimated to result in ~1 billion
cases of flu, ~3–5 million cases of severe illness and 300 000–500 000 deaths
annually.
 Seasonal influenza epidemics can cause febrile illnesses that range in severity
from mild to debilitating and can lead in some instances to hospitalization and
even cause death, mainly among high-risk groups, mostly occur as a

3. consequence of fulminant viral pneumonia or of secondary respiratory
bacterial infections.
Q.Who can get influenza?
 Anyone, including healthy people, can get the flu, and people of any age can
develop serious problems related to flu.
 The highest risk of complications from influenza occurs especially, in the very
young children, the elderly, those with pre-existing medical conditions and
pregnant women but even healthy people can get severe influenza.
Q.When is influenza activity highest?
 Although influenza epidemics occur yearly, the timing, severity, and length of the
season vary from year to year.
 In the Northern Hemisphere, the season is generally from October to May, with
peak activity in January or February, whereas in the Southern Hemisphere, it is
generally from May to October, with peak activity in July or August.
Q.What is the best way to prevent influenza ?
 Influenza vaccination is the primary tool to prevent influenza infection rather
than antiviral chemoprophylaxis.
 The protection of influenza vaccine depends on inducing humoral immunity,
namely neutralizing antibodies against viral capsular antigens, which boost the
immune system against the serotypes included in the vaccine.
Influenza (flu) is a contagious respiratory disease that can lead to serious
complications, hospitalization, or even death. Anyone can get the flu, including
people who are otherwise healthy and vaccination is the single best way to
prevent influenza and its complications.

4. Q.How influenza viruses change ?
 Influenza viruses are constantly changing , The antigenic evolution of influenza
viruses forms the primary basis for the occurrence of seasonal influenza
epidemics and occasional pandemics.
 Influenza viruses can change in two different ways , both antigenic drift and
antigenic shift are terms used to describe ways in which the flu viruses change
over time , A drift is a minor change while a shift is a major one.
"Antigenic drift"
o Occurs through relatively minor genetic changes to the H and N genes of both
influenza A and B that happen continually over time, and as they lack a poof-
reading mechanism , the small errors that occur when the virus copies itself
are left uncorrected.
o When a flu virus mutates or changes slightly, new strains of influenza viruses
appear and replace older strains.
o As it looks different to our immune system, when a new strain of human
influenza virus emerges, antibody protection that may have developed after
infection or vaccination with an older strain may not provide protection
against the new strain. Thus, the influenza vaccine is updated on a yearly basis
to keep up with the changes in influenza viruses.
o Seasonal influenza viruses evolve continuously (antigenic drift), which means
that people can get infected multiple times throughout their lives. Therefore
the components of seasonal influenza vaccines are reviewed frequently
(currently biannually) and updated periodically to ensure continued
effectiveness of the vaccines.
o In most years, one or two of the three virus strains in the influenza vaccine are
updated to keep up with the changes in the circulating flu viruses, this usually
requires seasonal influenza vaccines to be reformulated annually..
" Antigenic shift"
o An abrupt, major change in the influenza A viruses, resulting in a new influenza
virus subtype that can infect humans and has a hemagglutinin protein or
hemagglutinin and neuraminidase protein combination that has not been seen

5. in humans before & to which general populations are immunologically naïve..
o New subtypes of influenza A virus can emerge among humans through direct
transmission of an animal influenza virus to humans “Adaptive mutation ” or
through “Reassortment ” or genetic exchange of genes derived from an
animal influenza virus (e.g avian viruses) and a human influenza virus during
co-infection of a human or pig (serving as a mixing vessel) .
o Antigenic shift results in a new influenza A subtype , If it is introduced into the
human population, if most people have little or no protection against the new
virus, and if the virus can spread easily from person to person, a pandemic
(worldwide spread) may occur .
 Influenza viruses are changing by antigenic drift all the time, but antigenic
shift happens only occasionally.
 Influenza type A viruses undergo both kinds of changes, influenza type B
viruses change only by the more gradual process of antigenic drift.
Q.Why do I need a flu vaccine every year?
 Every flu season is different, A flu vaccine is needed every season for two reasons:
First, the body’s immune response from vaccination declines over time, so an
annual vaccine is needed for optimal protection , Even if the strains have not
changed, getting influenza vaccine every year is necessary to maximize
protection.
 Second, because flu viruses are constantly changing (Antigenic drift) , which may
occur in one or more influenza virus strains, , the seasonal influenza vaccine must
be re-made (updated ) each year to protect against the most recent and most
commonly circulating viruses.
Q.What is the recommended composition of seasonal influenza
vaccines?
 Influenza vaccines are manufactured in two forms: Inactivated influenza
vaccines (IIVs) and live-attenuated virus vaccines (LAIVs).

6.  As the LAIV is not yet available in the Middle east, influenza vaccination
guidelines will focus on IIV (mainly TIV) .
 Traditional seasonal flu vaccines (called "trivalent" vaccines) protects against
the influenza viruses that research indicates will be most common during the
upcoming season & are made to protect against three strains, an influenza A
(H1N1) , and influenza A (H3N2) , and an influenza B virus.
Recommended composition of influenza virus vaccines for use in the
2016-2017 Northern hemisphere influenza season
The Trivalent inactivated seasonal influenza vaccines (TIV) include a mixture of 2
influenza A strains and 1 influenza B strain thought most likely to circulate in the
upcoming season.
– an A/California/7/2009 (H1N1)pdm09-like virus
– an A/Hong Kong/4801/2014 (H3N2)-like virus
– a B/Brisbane/60/2008-like virus (B/Victoria lineage).
 Recently, from 2015 in USA & Australia , a newer quadrivalent influenza
vaccines (QIV) contain the same strains as trivalent vaccine (TIV) plus an
additional second B strain has been introduced.
Q.How are the vaccines made?
 Each year, before influenza season starts, one or more virus strains in the
vaccine might be changed and based on the global surveillance data for
influenza viruses ,the World Health Organization recommends the strains that
they believe will, be circulating in the upcoming influenza season.
 To ensure optimal vaccine efficacy against prevailing strains in both the
northern and southern hemispheres, the antigenic composition of the vaccines
is revised twice annually and adjusted to the antigenic characteristics of
circulating influenza viruses.

7.  The recommendations are based on informations collected from more than
100 national influenza centers in over 100 countries that conduct year-round
influenza surveillance.
 In February, the World Health Organization makes recommendations
concerning the virus strains to be included in vaccine production for the
forthcoming winter in the Northern Hemisphere,It takes about 6 months for
vaccine manufacturers to grow the viruses in chicken eggs
 Flu vaccine is produced by private manufacturers, and the timing of availability
depends on when production is completed, shipments began in August and
will continue throughout September and October until all vaccine is
distributed.
 A second recommendation is made in September which relates to vaccines to
be used for the winter in the Southern Hemisphere
Q.When should I get Seasonal Influenza Vaccine?
 People get vaccinated against influenza as soon as vaccine becomes available in
their community, if possible by October.
 In general vaccination before December is best since this timing ensures that
protective antibodies are in place before flu activity is typically at its highest.
However, flu season can last as late as May so getting vaccinated later throughout
the flu season , even in January or later, could still provide protective benefit.
Q.How do seasonal influenza vaccines work?
 The standard flu vaccine (or, the "flu shot") is made from flu viruses that have
been grown on fertilized chicken eggs. The viruses are killed during
manufacturing, a process known as “inactivation.” These inactivated viruses are a
source of proteins or antigens that trigger a protective antibody response.
 The vaccine is generally effective against the influenza virus within two weeks of
administration, Antibodies against flu viruses may last for six months or longer,
and sometimes even up to one year.

8.  The vaccine is only effective against the strains of the virus that match the vaccine
Q.What does vaccine “match” and “mismatch” mean?
 Influenza viruses are constantly changing, including during the time between
vaccine virus selection and the influenza season or they can even change within
the course of one flu season.
 If these changes lead to antigenic differences between the circulating seasonal
influenza viruses and those viruses that are included in the seasonal influenza
vaccine, then the vaccine and circulating viruses may not be closely related
“vaccine mismatch”.
 The degree of similarity or difference between the circulating viruses and the
viruses in the vaccines is often referred to as “vaccine match” or “vaccine
mismatch”.
Q. Can the vaccine provide protection even if the vaccine is not a "good"
match?
 It's not possible to predict with certainty which flu viruses will predominate during
a given season, there is always the possibility of a less than optimal match
between circulating viruses and the viruses in the vaccine.
 It’s important to remember that even when the viruses are not closely matched,
the vaccine can still protect many people and prevent flu-related complications.
Such protection is possible because antibodies made in response to the vaccine
can provide some protection (called cross-protection) against different, but
related strains of influenza viruses.
 In addition, even when there is a less than optimal match or lower effectiveness
against one virus, it's important to remember that the flu vaccine is designed to
protect against three flu viruses.
 For these reasons, even during seasons when there is a less than optimal match, it
is recommended to give annual flu vaccination (or re-vaccination, if the vaccine
strains are identical) , This is particularly important for people at high risk for
serious flu complications, and their close contacts.

9. Q. How much protection does the seasonal influenza vaccine provide?
 The ability of flu vaccine to protect a person (vaccine effectiveness) depends
on various factors, including the age and health status of the person being
vaccinated, and also the similarity or “match” between the viruses used to
make the vaccine and those circulating in the community.
 During seasons when most circulating influenza viruses are similar to the
viruses in the influenza vaccine, the vaccine can reduce the risk of illness
caused by influenza virus infection by about 50-60% among the overall
population.
 The vaccine effectiveness may be lower among persons with chronic medical
conditions and among the elderly, as compared to healthy young adults and
children.
Q. Can people still get influenza if they have had the influenza vaccine?
 Protection is never 100%, and some people can still get the flu after being
vaccinated. It is possible to get influenza-like illness even if you have been
vaccinated because of the following reasons:
1. Since it takes about two weeks to build protective antibodies after
receiving the vaccine, it is possible for someone to become infected in that
time period or shortly before getting vaccinated. This can result in
someone erroneously believing they developed the disease from the
vaccination.
2. You may be exposed to a virus not included in the vaccine and develop
illness.
3. Respiratory pathogens that are not related to influenza viruses can cause
“flu-like” symptoms (such as rhinovirus). The influenza vaccine does not
protect you against these pathogens.
4. Unfortunately, some people can remain unprotected from flu despite
getting the vaccine ,This is more likely to occur among people that have
weakened immune systems ,However, even among people with weakened
immune systems, the flu vaccine can still help prevent influenza
complications.

10. Q. WHO should get vaccinated?
 WHO recommends annual seasonal influenza vaccination for:
a) Highest priority group.:
Pregnant women (at any stage of pregnancy)
b) 4 other priority groups (in no order of priority) are:
1. Health-care workers
2. Children aged 6 months to 5 years
3. Elderly(≥65 years of age)
4. Individuals with specific chronic medical condition
Medical conditions that are associated with an increased risk of influenza
disease complications and for which individuals are eligible for vaccination
Cardiac diseases  Coronary artery disease
 Congestive heart failure
 Cyanotic congenital heart disease
Chronic pulmonary disorders  Bronchial asthma
 Chronic obstructive pulmonary disease (COPD)
 Bronchiectasis
 Suppurative lung disease
 Cystic fibrosis
Chronic neurological
conditions
 Hereditary and degenerative CNS diseases (including
multiple sclerosis)
 Seizure disorders
 Spinal cord injuries
 Neuromuscular disorders
Immunocompromising
conditions
 Immunocompromised due to disease or treatment
(e.g. malignancy, transplantation and /or chronic
steroid use ,immunosuppressive drugs)
 Asplenia or splenic dysfunction
 HIV infection
Diabetes & metabolic
disorders

11. Haematological disorders  Haemoglobinopathies
Chronic Renal disease  Chronic renal failure
Chronic liver disease  Defined as histological evidence of fibrosis or cirrhosis, or
clinical evidence of chronic liver cell failure.
Morbid Obesity  Defined as body mass index (BMI) ≥40 kg/m2
Health care workers (HCWs) should use every opportunity to give
Inactivated seasonal influenza vaccine to individuals at risk who have not
been immunized during the current season, even after influenza activity has
been documented in the community
 Health-care workers are an important priority group for influenza vaccination,
not only to protect the individual and maintain health-care services during influenza
epidemics, but also to reduce spread of influenza to vulnerable patient groups,
Vaccination of HCWs should be considered part of a broader infection control policy
for health-care facilities.
 In the absence of contraindications, refusal of HCWs who have direct patient
contact to be immunized annually against influenza implies failure in their duty of
care to patients.
Q. Should pregnant women receive the trivalent inactivated influenza
vaccine?
 When compared with nonpregnant women, pregnant women infected with
influenza virus are prone to severe illnesses with higher morbidity and
mortality.They also have a greater risk for serious problems for their infants and

12. during delivery. Hence, seasonal influenza vaccine is commonly used during
pregnancy.
 Pregnant women, both healthy pregnant women and those with chronic health
conditions, are at increased risk of influenza related complications and
hospitalization. (The risk increases with length of gestation i.e. it is higher in the
third than in the second trimester)
 Infants born during influenza season to vaccinated women are less likely to be
premature, small for gestational age, and low birth weight , there is no evidence
that influenza vaccine causes any harm to mother or baby when administered to a
pregnant woman.
 Trivalent inactivated Influenza vaccine is considered safe for use in pregnant
women at at any stage of pregnancy, WHO considers pregnant women as a high
priority group and recommends immunization.
 Furthermore, Children aged <6 months are not eligible to receive currently
licensed influenza vaccines and should be protected against influenza through
vaccination of their mothers during pregnancy (via passive transfer of antibodies
across the placenta and through breast milk).
 Pregnant women should receive inactivated vaccine (flu shot) but should NOT
receive the live attenuated vaccine (nasal spray).
Q. Is trivalent inactivated influenza vaccine safe for breastfeeding
mothers?
 Yes. The trivalent inactivated vaccine (TIV) is safe for breastfeeding mothers and
their babies (via breast milk) ,Women who are breastfeeding may receive either
either inactivated vaccine or live attenuated vaccine (nasal spray)
Pregnancy and breast-feeding are not considered contraindications to
inactivated seasonal influenza vaccination

13. Q. How does trivalent inactivated influenza vaccine given & What is the
dosage and frequency of administration ?
Dose:
 A full dose (0.5 mL) of influenza vaccine should be used for all age groups ,
including children 6 to 35 months of age who are receiving influenza
immunization.
 Contrary to dosing information in product monographs, the National Advisory
Committee on Immunization (NACI) is no longer recommending 0.25 mL doses
for children 6 to 35 months of age.
 This recommendation is based on evidence showing improved antibody
response without increase in reactogenicity in children receiving the 0.5 mL
dose , so children receiving 0.25 mL doses will be considered inadequately
immunized.
Site of administration:
 TIV should be administered intramuscularly (IM).
 The anterolateral thigh is the recommended site in infants 6 -12 months of age.
 The deltoid muscle is the recommended site in adults and children over 12
months of age (nursing assessment is required to determine if the deltoid
muscle mass is of sufficient size).
frequency of administration:
 Children 6 months to <9 years of age receiving seasonal influenza vaccine for
the first time should be given two doses, with a minimum interval of four
weeks between doses, they are then recommended to receive one dose per
year thereafter.
 Adults and Children who have been previously immunized with seasonal
influenza vaccine are to receive one dose of influenza vaccine each year.
**Children less than 9 years of age require 2 doses given at a minimum of 4 weeks apart if they have never received
seasonal influenza vaccine in a previous year.

14. Q. How should influenza vaccines be stored ?
 All influenza vaccines must be maintained at refrigerator temperature (2°C to
8°C) at all times during handling, storage and transport.
 Vaccine should not be stored in the refrigerator door or crisper compartment
and frequent opening of the refrigerator door should be avoided.
 The vaccine should not be frozen.
 Vaccine should be transported in an insulated container with ice packs.
 Vaccine should be stored in original packaging in order to be protected from
light.
Q. Can inactivated seasonal influenza vaccine be administered
simultaneously with other vaccines?
 Injectable inactivated seasonal influenza vaccine does not interfere with the
effectiveness of other vaccines, it can be given at the same time or at any time
before or after administration of other inactivated vaccines (e.g. Hepatitis B
vaccine) or live attenuated vaccines (e.g. Measles,mumps and rubella vaccine).
 For concomitant parenteral injections, different injection sites and separate
needles and syringes should be used.
Q. Can the inactivated vaccine cause influenza?
 No. . Neither the injectable (inactivated) vaccine nor the live attenuated (nasal
spray) vaccine can cause influenza , The injectable influenza vaccine contains
only killed viruses and cannot cause influenza disease.
 Fewer than 1% of people who are vaccinated develop influenza-like symptoms,
such as mild fever and muscle aches, after vaccination , These side effects are
not the same as having the actual disease.

15. Q. What are the side effects of the flu shot?
In general, Flu shots are safe and well-tolerated
1. local side effects (Injection site reactions) :
 Swelling ,redness and pain at the injection site, are common after receiving
inactivated influenza vaccine and occur in more than 10% of people.
 Fever, tiredness and myalgia (muscle aches) also occur commonly (1–10%) .
 Injection site reactions are common but are generally classified as mild and
transient ,These side effects may commence within a few hours of
vaccination and can last for 1–2 days.
 In children aged <5 years, these adverse events may be more pronounced.
 Post-vaccination symptoms may mimic influenza ,Experiencing these non-
specific side effects does not mean that you are getting influenza.
2. As with any vaccine, there is an extremely rare possibility of a life-threatening
allergic reaction called anaphylaxis :
 This can include hives, difficulty breathing, or swelling of the throat, tongue
or lips. For this reason it is important to stay in the clinic for 15 minutes after
getting any vaccine.
 This reaction can be treated, and occurs in less than 1 in a million people
who get the vaccine.
3. Guillain-Barré syndrome:
 In very rare instances , the flu shot has been associated with Guillain-Barré
Syndrome (GBS) , about 1 case per million doses /year from influenza
vaccine.
 However, the potential risk of GBS recurrence associated with influenza
vaccination must be balanced against the risk of GBS associated with
influenza infection itself.
 The risk of GBS associated with influenza infection is larger than that
associated with influenza vaccination.

16. 4. Oculo-respiratory syndrome (ORS):
 During the 2000/2001 influenza season, Health Canada had received an
increased number of reports of vaccine-associated symptoms and signs
that were subsequently described as oculorespiratory syndrome (ORS)
 ORS is defined as the presence of bilateral red eyes plus one or more
respiratory symptoms (cough, wheeze, chest tightness, difficulty
breathing, difficulty swallowing, hoarseness or sore throat) with or without
facial oedema ,that starts within 24 hours of vaccination, , and generally
resolving within 48 hours of symptom onset,symptoms are typically mild
and resolve quickly without specific treatment
 Oculorespiratory Syndrome (ORS) was found during the 2000-2001
influenza season, few cases have been reported since then
 Recommendations for subsequent immunization following a report of ORS
are based on a risk/benefit assessment and the severity of symptoms as
perceived by the individual who experienced the symptoms.
Q. Who should NOT be given the trivalent inactivated influenza vaccine?
Anyone who has:
1. had a life-threatening anaphylactic reaction to a previous dose of influenza
vaccine, or to any of the vaccine components with the exception of egg .
( NOTE - Egg allergy is no longer considered a reason not to get the flu vaccine).
2. had developed Guillain-Barré Syndrome (GBS) within six weeks of a previous
dose influenza vaccination
3. had experienced severe Oculorespiratory Syndrome (ORS ) that included
lower respiratory symptoms within 24 hours of receiving influenza vaccine
(pending consultation with the Medical Officer of Health to review the risks
and benefits of further influenza immunization) .
4. Inactivated influenza vaccines are not licensed for use in infants less than 6
months of age.

17. Precautions:
 Postpone vaccination in persons with serious acute illness until their symptoms
have resolved (there is no need to delay vaccination because of minor illness, such
as a cold, with or without fever) .
Administration of influenza vaccine to egg allergic persons:
 Influenza vaccines are grown in eggs and there has been concern that residual
egg protein (ovalbumin) could cause allergic reactions in egg-allergic recipients.
However, all studies to date have suggested that this risk is very low.
 Due to changes in vaccine manufacturing , the amount of egg protein in the
majority of influenza vaccines has been reduced.
 People with egg allergy, including egg-induced anaphylaxis, can usually be safely
vaccinated with inactivated influenza vaccines that have less than 1 μg of residual
egg ovalbumin per dose.
 The Product Information of the vaccine to be given should be checked for the
vaccine’s ovalbumin content prior to vaccine administration.
 The risk of an allergic reaction to influenza vaccine in patients with egg allergy is
very low, likely due to the very low amount of ovalbumin in the vaccines. Any such
theoretical risk is far outweighed by the very real risk of such patients remaining
unvaccinated. Thus all patients with egg allergy of any severity, including
anaphylaxis, should receive influenza vaccine. Skin testing with the vaccine and
dividing the dose are not necessary.
 Even though the risk of anaphylaxis associated with influenza vaccination of a
person with egg allergy is very low, it is essential that such patients are vaccinated
in facilities with staff that are able to recognise and treat anaphylaxis.
 Egg-allergic individuals should receive inactivated influenza vaccine in a setting
where anaphylaxis can be recognized and treated and should be observed for 30
minutes after vaccination.. Egg allergic individuals should not receive their
influenza vaccine from a pharmacy or other non-medical office setting

18.  To deal with anaphylactic or hypersensitivity reactions, immediate treatment,
including epinephrine 1:1000, should be easily accessible during the administration
of the vaccine.
Egg allergy is no longer considered a contraindication for TIV. Those with
confirmed egg anaphylaxis and non-anaphylactic egg allergy can be given an
influenza vaccine with an ovalbumin content <0.1μg per dose.
Flu Vaccines are very safe , effective and have been used for more than
60 years, It is much safer to get the vaccine than to get
Influenza illness.

19. References
1. Vaccine effectiveness estimates for seasonal influenza vaccines -WHO
February 2015
2. Recommended composition of influenza virus vaccines for use in the 2016-2017
northern hemisphere influenza season -WHO February 2016
3. Global Advisory Committee on Vaccine Safety (GACVS) ,information sheet
,observed rate of influenza vaccine reactions -WHO July 2012
4. Vaccines against influenza , WHO position paper – November 2012
5. Seasonal Influenza - Fact sheet –WHO-March 2014
6. National Advisory Committee on Immunization (NACI) -Statement on Seasonal
Influenza Vaccine for 2013-2014- Public Health Agency of Canada
7. Influenza Surveillance Protocol For Ontario Hospitals-July 2014
8. Influenza (Flu) Vaccines Fact sheet- Toronto Public Health - September 2014
9. Immunization Action Coalition Saint Paul, Minnesota-2015
10. Alberta Health Services Immunization Program Revised December 15, 2014
11. Canadian Immunization Guide - National Advisory Committee on Immunization
(NACI)† Statement on Seasonal Influenza Vaccine for 2015-2016
12. Update on Egg Allergy and Influenza Vaccine (Nov 2011) - Centers for Disease
Control and Prevention(CDC) Advisory Committee on Immunization Practices
(ACIP) 2011 and the American Academy of Pediatrics’ (AAP) Committee on
Infectious Diseases 2011
13. Centers for Disease Control and Prevention(CDC) - ACIP 2015-2016 influenza
vaccine guidelines
14. Influenza vaccines for Australians | NCIRS Fact sheet: July 2015
15. Community case management during an influenza outbreak- WHO 2011

20. Health care workers (HCWs) should use every opportunity to give
Inactivated seasonal influenza vaccine to individuals at risk who have not been
immunized during the current season, even after influenza activity has been
documented in the community
.

23. Flu vaccine can:
Keep you from getting flu,
Make flu less severe if you do get it, and
Keep you from spreading flu to your family and other people.