1. Influenza and Influenza Vaccine
Epidemiology and Prevention of Vaccine-Preventable Diseases
National Center for Immunization and Respiratory Diseases
Centers for Disease Control and Prevention
Revised May 2009

2. Influenza Antigenic Changes
Antigenic Shift
major change, new subtype
caused by exchange of gene segments
may result in pandemic
Example of antigenic shift
H2N2 virus circulated in
H3N2 virus appeared in 1968 and completely replaced H2N2 virus

3. Influenza Antigenic Changes
Antigenic Drift
minor change, same subtype
caused by point mutations in gene
may result in epidemic
Example of antigenic drift
in , A/Panama/2007/99 (H3N2) virus was dominant
A/Fujian/411/2002 (H3N2) appeared in late 2003 and caused widespread illness in

4. Influenza Clinical Features
Incubation period 2 days (range 1-4 days)
Abrupt onset of fever, myalgia, sore throat, nonproductive cough, headache
Severity of illness depends on prior experience with related variants

5. Influenza Complications
Pneumonia
secondary bacterial
primary influenza viral
Reye syndrome
Myocarditis
Death per 1,000 cases

6. Impact of Influenza-United States, 1990-1999
Approximately 36,000 influenza-associated deaths during each influenza season
Persons 65 years of age and older account for more than 90% of deaths
Higher mortality during seasons when influenza type A (H3N2) viruses predominate

7. Impact of Influenza-United States, 1990-1999
Highest rates of complications and hospitalization among young children and person 65 years and older
Average of more than 200,000 influenza-related excess hospitalizations
57% of hospitalizations among persons younger than 65 years of age
Greater number of hospitalizations during type A (H3N2) epidemics

8. Influenza Among School-Aged Children
typically have the highest attack rates during community outbreaks of influenza
serve as a major source of transmission of influenza within communities

9. Month of Peak Influenza Activity United States, 1976-2008
47%
19%
13%
13% 3% 3%
MMWR 2006;55:22

10. Influenza Vaccines Inactivated subunit (TIV) intramuscular trivalent
split virus and subunit types
duration of immunity 1 year or less
Live attenuated vaccine (LAIV)
intranasal
duration of immunity at least 1 year

11. Inactivated Influenza Vaccine Efficacy
70%-90% effective among healthy persons younger than 65 years of age
30%-40% effective among frail elderly persons
50%-60% effective in preventing hospitalization
80% effective in preventing death

12. Influenza and Complications Among Nursing Home Residents
Vaccinated*
Unvaccinated
RR=1.9
RR=2.0
RR=2.5
RR=4.2
*Inactivated influenza vaccine. Genesee County, MI,

13. LAIV Efficacy in Healthy Children
87% effective against culture-confirmed influenza in children 5-7 years old
27% reduction in febrile otitis media (OM)
28% reduction in OM with accompanying antibiotic use
Decreased fever and OM in vaccine recipients who developed influenza

14. LAIV Efficacy in Healthy Adults
20% fewer severe febrile illness episodes
24% fewer febrile upper respiratory illness episodes
27% fewer lost work days due to febrile upper respiratory illness
18%-37% fewer days of healthcare provider visits due to febrile illness
41%-45% fewer days of antibiotic use

15. Timing of Influenza Vaccine Programs
Influenza activity can occur as early as October
In more than 80% of seasons since 1976, peak influenza activity has not occurred until January or later
In more than 60% of seasons the peak was in February or later

16. Timing of Influenza Vaccine Programs
Providers should begin offering vaccine soon after it becomes available, if possible by October
To avoid missed opportunities for vaccination, providers should offer vaccine during routine healthcare visits or during hospitalizations whenever vaccine is available

17. Inactivated Influenza Vaccine Schedule
Dose
0.25 mL
0.50 mL
Age
Group
6-35 mos
3-8 yrs
>9 yrs
No.
Doses
1* or 2 1
*Only one dose is needed if the child received 2 doses of influenza vaccine during the previous influenza season

18. Influenza Vaccination of Children
Children 6 months through 8 years of age who did not receive the recommended second dose of influenza vaccine in the initial year that they received influenza vaccine should receive 2 doses during the next influenza season*
Children 6 months through 8 years of age who are being vaccinated two or more seasons after receiving an influenza vaccine for the first time should receive a single annual dose, regardless of the number of doses administered previously
*applies only to the influenza season that follows the first season that a child younger than 9 years receives influenza vaccine

19. Influenza Vaccination Schedule
• All children younger than 9 years receiving seasonal influenza vaccine for the first time this season should receive 2 doses, separated by 4 weeks • Children younger than 9 years who received a seasonal vaccine for the first time last season but who received only 1 dose should receive 2 doses this season
MMWR 2010;59 (early release) From the Immunization Update webcast (originally broadcast August 5, 2010

20. Influenza Vaccination Schedule
• Children younger than 9 years who did not receive at least 1 dose of a 2009 monovalent vaccine should receive 2 doses of seasonal vaccine this season • Children younger than 9 years whose 2009 pandemic vaccine history is not known should receive 2 doses this season
MMWR 2010;59 (early release) From the Immunization Update webcast (originally broadcast August 5, 2010

21. Live Attenuated Influenza Vaccine Indications
Healthy*, nonpregnant persons 2 through 49 years of age, including
healthy children
healthcare personnel
persons in close contact with high-risk groups
persons who want to reduce their risk of influenza
*Persons who do not have medical conditions that increase their risk for complications of influenza

22. Fluzone High-Dose TIV
• Approved only for persons 65 years of age or older • Each dose contains 4 times as much hemagglutinin as the regular formulation of Fluzone for adults • ACIP has not expressed a preference for the high dose Fluzone formulation or any other inactivated vaccine for use in persons 65 years and older
MMWR 2010;59 (early release) From the Immunization Update webcast (originally broadcast August 5, 2010

23. Inactivated Influenza Vaccine Adverse Reactions
Local reactions 15%-20%
Fever, malaise not common
Allergic reactions rare
Neurological very rare reactions

24. Live Attenuated Influenza Vaccine Adverse Reactions
Children
no significant increase in URI symptoms, fever, or other systemic symptoms
significantly increased risk of asthma or reactive airways disease in children months of age
Adults
significantly increased rate of cough, runny nose, nasal congestion, sore throat, and chills reported among vaccine recipients
no increase in the occurrence of fever
No serious adverse reactions identified
These symptoms were reported in 10 to 40 percent of both vaccine and placebo recipients. LAIV not licensed for children <60 months of age.

25. Inactivated Influenza Vaccine Contraindications and Precautions
Severe allergic reaction to a vaccine component (e.g., egg) or following a prior dose of vaccine
Moderate or severe acute illness
History of Guillian Barré syndrome within 6 weeks following a previous dose of TIV (precaution)

26. Live Attenuated Influenza Vaccine Contraindications and Precautions
Children younger than 2 years of age*
Persons 50 years of age or older*
Persons with chronic medical conditions*
Children and adolescents receiving long-term aspirin therapy*
*These persons should receive inactivated influenza vaccine

27. Live Attenuated Influenza Vaccine Contraindications and Precautions
Immunosuppression from any cause*
Pregnant women*
Severe (anaphylactic) allergy to egg or other vaccine components
History of Guillian-Barré syndrome
Children younger than 5 years with recurrent wheezing*
Moderate or severe acute illness
*These persons should receive inactivated influenza vaccine