Influenza Infection Health Risks and Influenza Vaccination

Seasonal Influenza epidemics cause significant morbidity and mortality worldwide. The World Health Organization puts the global burden of the disease at 3-5 million cases of severe illness with around 250,000 to 500,000 deaths annually (1). In the United States alone, the Centers for Disease Control (CDC) estimate that between 5-20% of the population contracts influenza annually with more than 200,000 hospitalizations for complications from the virus (2).

History of Influenza Virus and Flu Vaccination

In 1933, researchers discovered that influenza was a viral illness. Shortly thereafter, in 1938, Jonas Salk and Thomas Francis created the first influenza vaccine (3). In the 1940s, a vaccine against the strains influenza A and B was created using embroynated chicken eggs − a technique for vaccine creation still in use today (4). Effective for only two seasons due to antigenic drift, the necessity to reformulate the vaccine prompted the World Health Organization to create an influenza surveillance network to identify drifted strains (5). Since 1973, the WHO has provided recommendations on the composition of the influenza vaccine using data provided via this Global Influenza Surveillance Network (6). The most recent recommendations from the WHO for composition of the vaccine are available on their website (7).

Influenza vaccines

Most of the current seasonal vaccines include 3 influenza strains − two A strains and one B strain − although a vaccine containing two strains of each is also available. These are created using embroynated eggs or, more recently, through cell cultures (5, 8, 9). The vaccine is available in several formulations − including trivalent inactivated vaccines (TIV), live attenuated influenza vaccines (LAIV) and quadrivalent LAIV − with TIVs administered via intramuscular injection and the latter available as nasal spray (5, 8, 9).

As the influenza seasons occur at different times in the northern and southern hemispheres, vaccine composition is revised twice per year based on data from the WHO global influenza surveillance network in order to optimize efficacy against the prevailing strains in each region (8).

Influenza vaccination recommendations by WHO and CDC

The Centers for Disease Control and Prevention in the United States (CDC) recommends routine annual influenza vaccination for all persons older than 6 months, with exception for individuals for whom it is contraindicated (9). Similarly, the World Health Organization recommends routine vaccination with priority given to pregnant women, children aged 6-59 months, the elderly, and individuals with specific chronic medical conditions, and suggests that vaccination is particularly important for health care workers and people who are at high risk for serious complications from influenza (9). Like the WHO, the CDC also suggests prioritizing vaccination for individuals at high risk for developing complications from influenza, including pregnant women, children, and the elderly, and suggests individuals with such medical conditions as asthma, heart disease, kidney, liver or blood disorders should also be vaccinated (see the CDC website for a full list of individuals considered high risk) (10).

CDC-recommended best practice is to provide the vaccination before onset of influenza activity in the community and should continue as long as viruses are circulating (11). Patients are encouraged to discuss with their physicians regarding any questions related to flu vaccination, particularly if they have an egg allergy, if they are feeling unwell already, or have ever had Guillain-Barré Syndrome (12).

Influenza vaccination effectiveness

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months (13). Each season since 2004−05, CDC has estimated the effectiveness of seasonal influenza vaccine in preventing medically attended acute respiratory illness (ARI) associated with laboratory-confirmed influenza. This season, early estimates of influenza vaccine effectiveness are possible because of widespread, early circulation of influenza viruses. By January 3, 2015, 46 states were experiencing widespread flu activity, with predominance of influenza A (H3N2) viruses (14). This report presents an initial estimate of seasonal influenza vaccine effectiveness at preventing laboratory-confirmed influenza virus infection associated with medically attended ARI based on data from 2,321 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (Flu VE) during November 10, 2014−January 2, 2015. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self−rated health, and days from illness onset to enrollment) against laboratory-confirmed influenza associated with medically attended ARI was 23% (95% confidence interval [CI] = 8%−36%). This interim VE estimate is relatively low compared with previous seasons when circulating viruses and vaccine viruses were well-matched and likely reflects the fact that more than two-thirds of circulating A (H3N2) viruses are antigenically and genetically different (drifted) from the A (H3N2) vaccine component of 2014−15 Northern Hemisphere seasonal influenza vaccines (14).

Globally, in data collected by the WHO from April through August 2015 for countries in the Southern Hemisphere, interim estimates of vaccine effectiveness were reported for three countries: Australia, New Zealand and South Africa. Estimates ranged from a low of 23% effectiveness against influenza A in ambulatory patients in both New Zealand and South Africa to a high of 87% for inpatients against H1N1 (15).

In the Northern hemisphere, WHO estimates of vaccine effectiveness for the 2014-15 season included data from the USA, Canada, the UK and Spain, focusing on prevention of laboratory-confirmed infections with influenza A. For the A strain, effectiveness estimates ranged from a low of 3% in the UK to a high of 55% in Spain. In influenza B, interim effectiveness estimates were provided only for the USA (45%) and Spain (61%) (16).

These early, low VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with the currently circulating A (H3N2) viruses as well as other viruses that might circulate later in the season, including influenza B viruses. Even when VE is reduced, vaccination still prevents some illness and serious influenza-related complications, including thousands of hospitalizations and deaths (17). Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated, including persons who might already have been ill with influenza this season.

Key Message

Influenza Viral infection is cause of significant morbidity and mortality, especially for high-risk population group. According to WHO data, there is an increase in influenza activity in the western Asia region, including Qatar (18).

The influenza vaccine was developed to provide immunity against certain viral strains each year. The WHO and CDC recommend annual vaccination for high−risk population. One Canadian study showed that the strongest predictor of intention to recommend the H1N1 vaccine to patients was the health professional’s own intention to be vaccinated (19).

In Qatar, the national immunization program under Supreme Council of Health (SCH) follows World Health Organization (WHO) recommendations and provides vaccination programs to public and all health care providers (HCPs) accordingly. Current WHO and CDC recommendation are that all health care providers need to receive annual flu vaccination. The ideal vaccination rate among HCPs is 100%, but a study has suggested that vaccination of 80% of HCPs is sufficient to reduce transmission and provide herd immunity in a safe level within healthcare facilities (20). US Department of Health and Human Services has set a future target goal to reach an influenza vaccination rate of 90% by 2020 (21).

In 2006, Qatar’s largest tertiary care center, Hamad Medical Center (HMC), started an influenza vaccine campaign. HMC infection control department data showed consistent low compliance with influenza vaccination despite conducting the vaccine campaign yearly and with easy accessibility. In a 2015 pediatric influenza vaccination study, the vaccination coverage among health care providers was higher (67.7%) than previously reported rates, however, the concerning part is that there was a statistically lower percentage of HCP who were willing to retake the seasonal flu vaccine (19). To decrease influenza-related morbidity and mortality, we all − health care providers and other community members − need to work together with SCH and other health institutions to continue improving the influenza vaccination rate in our Qatar community.

References and for further reading:

  1. World Health Organization. Factsheet No. 211: Influenza (Seasonal) 2014 [Available here]
  2. Centers for Disease Control and Prevention. Seasonal influenza Q&A 2015 [Available here]
  3. Davis CP. Flu Vaccine (Seasonal and Pandemic Flu) 2015 [Available here]
  4. Crovari P, Alberti M, Alicino C. History and evolution of influenza vaccines. J Prev Med Hyg. 2011;52(3):91-4.
  5. Krammer F, Palese P. Advances in the development of influenza virus vaccines. Nat Rev Drug Discov. 2015;14(3):167-82.
  6. World Health Organization. Influenza: Influenza vaccine viruses and reagents 2015 [Available here]
  7. World Health Organization. WHO recommendations on the composition of influenza virus vaccines 2015 [Available here]
  8. Vaccines against influenza WHO position paper - November 2012. Wkly Epidemiol Rec. 2012;87(47):461-76.
  9. Centers for Disease Control and Prevention. Vaccination: Who Should Do It, Who Should Not and Who Should Take Precautions 2015 [Available here]
  10. Centers for Disease Control and Prevention. People at High Risk of Developing Flu–Related Complications 2015 [Available here]
  11. Centers for Disease Control and Prevention. Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2015–16 Influenza Season. Morbidity and Mortality Weekly Report (MMWR). 2015 Aug 7;64(30):818-25.
  12. Prevention CfDCa. Vaccination: Who Should Do It, Who Should Not and Who Should Take Precautions 2015 [Available here]
  13. Grohskopf LA, Olsen SJ, Sokolow LZ, Bresee JS, Cox NJ, Broder KR, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP) -- United States, 2014-15 influenza season. MMWR Morb Mortal Wkly Rep. 2014;63(32):691-7.
  14. Centers for Disease Control and Prevention. FluView: 2014-2015 Influenza Season Week 53 ending January 3, 2014 2015 [Available here]
  15. Sternal J, Hammond A, Besselaar T, Jackson S, Vandemaele K, Zhang W. Review of the 2015 influenza season in the southern hemisphere. Weekly Epidemiological Record. 2015;48(90):645-60.
  16. Hammond A, Gusbi N, Sosa P, Fitzner J, Besselaar T, Vandemaele K, et al. Review of the 2014-15 influenza season in the northern hemisphere. Weekly Epidemiological Record. 2015;23(90):281-96.
  17. Fry AM, Kim IK, Reed C, Thompson M, Chaves SS, Finelli L, et al. Modeling the effect of different vaccine effectiveness estimates on the number of vaccine-prevented influenza-associated hospitalizations in older adults. Clin Infect Dis. 2014;59(3):406-9.
  18. World Health Organization. Influenza update no. 231 2015 Nov 30 [Available here]
  19. Alhammadi A, Khalifa M, Abdulrahman H, Almuslemani E, Alhothi A, Janahi M. Attitudes and perceptions among the pediatric health care providers toward influenza vaccination in Qatar: A cross-sectional study. Vaccine. 2015;33(32):3821-8.
  20. Salgado CD, Giannetta ET, Hayden FG, Farr BM. Preventing nosocomial influenza by improving the vaccine acceptance rate of clinicians. Infect Control Hosp Epidemiol. 2004;25(11):923-8.
  21. National Vaccine Advisory Committee. Strategies to achieve the healthy people 2020 annual influenza vaccine coverage goal for health-care personnel: recommendations from the national vaccine advisory committee. Public Health Rep. 2013;128(1):7-25.

Written for January 2016 by
Sharda Udassi, MD, FAAP
Director of Quality and Safety, Pediatrics
Senior Attending Physician
Division of General Academic Pediatrics
Sidra Medical & Research Center
Qatar Foundation


Karen Neves MA, MLIS
Clinical Librarian
Library Services
Sidra Medical & Research Center
Qatar Foundation