Flu vaccine, even when just 20% effective, saves tens of thousands of lives

Each winter, many people wonder whether its worth getting a flu shot while health officials repeatedly warn against n...

Posted: May 1, 2018 8:49 AM
Updated: May 1, 2018 8:49 AM

Each winter, many people wonder whether its worth getting a flu shot while health officials repeatedly warn against not getting one.

Now a new study sheds light on the benefit of doing so. Even when the flu shot is just 20% effective it can still reduce US doctor visits due to illness by an estimated 20 million in a single year, the new report published in the scientific journal PNAS (Proceedings of the National Academy of Sciences of the United States) finds.

Based on US vaccination rate averages, the flu shot saves 61,000 people from death

Vaccination also prevents 129,000 hospitalizations

In addition, vaccination also can prevent thousands of hospitalizations and deaths, the study authors estimated based on the average vaccination coverage rate in the United States.

"Getting vaccinated against influenza is beneficial to the individual and to the community even when the vaccine is of relatively low efficacy," said Burton H. Singer, co-author of the study and an adjunct professor for the Emerging Pathogens Institute at University of Florida in Gainesville.

Caused by viruses, flu is a contagious respiratory illness with mild to severe symptoms that can sometimes lead to death. The flu virus evolves rapidly and new viruses circulate in different parts of the world, so each year scientists must reformulate the vaccine. Add to that an imperfect manufacturing process and even a 'good match' reformulation may not be as effective as scientists would like.

In fact, the Centers for Disease Control and Prevention estimated just 36% effectiveness for the 2017-18 seasonal vaccine as of February 3. (The season ends in May.)

For the new study, Singer and his colleagues created a mathematical model of flu transmission and vaccination to evaluate how much illness is prevented by even a very low effectiveness flu vaccine. The research team found that at the average rate of US coverage even a poor vaccine would prevent a significant amount of illnesses, hospitalizations and deaths.

For example, at just 43% coverage (the average rate of Americans who received a flu shot for the years 2012 through 2017), a vaccine with just 20% effectiveness could avert more than 20 million infections or illnesses as compared to not getting the vaccine. In addition, 129,000 hospitalizations and 61,000 deaths could be prevented.

Based on the model, if more people got a flu shot, say half of the US population, the same 20% effective flu shot would prevent an additional 3.63 million infections, 21,987 hospitalizations and 8,479 deaths.

"When a vaccine is fully effective on 50% or more of the people who are vaccinated, you need to primarily focus on vaccinating young children," said Singer. The reason? Children are still building immunity and they pass germs around at school.

"As efficacy of the vaccine decreases, it becomes increasingly important for the elderly to be vaccinated in addition to young children," said Singer, since the elderly are more likely to develop complications from the flu, such as pneumonia, which can be deadly.

The CDC reported a total of 160 flu-related deaths in children and 30,064 flu-related hospitalizations overall between October 1, 2017 and April 21, 2018. The highest rate of hospitalization occurred among adults 65 years old and older.

Richard Webby, a flu scientist who is part of the World Health Organization's advisory board and a member of St. Jude Children's Research Hospital's Department of Infectious Diseases, said "effectiveness estimates go up and down based on a number of factors including match of vaccine and circulating strain and probably other factors we don't fully understand."

"The take home message from the past few seasons is that there is much room for improvement," said Webby, who was not involved in the research.

Still, more people, particularly the elderly, need to get vaccinated even when the vaccine effectiveness is lower than hoped, Webby said: "This study suggests that even with a less than optimal vaccine there is still much public health benefit that can be achieved if these are used properly and widely."

Minnesota Coronavirus Cases

Data is updated nightly.

Cases: 449492

Reported Deaths: 6047
CountyCasesDeaths
Hennepin933031483
Ramsey40134741
Dakota33159344
Anoka31061365
Washington20220230
Stearns17922188
St. Louis13730242
Scott1199496
Wright11656104
Olmsted1054775
Sherburne822065
Carver696436
Clay653981
Rice610769
Kandiyohi554871
Blue Earth543233
Crow Wing484877
Otter Tail457967
Chisago453336
Benton421086
Winona390046
Douglas375766
Nobles371746
Mower367829
Goodhue349259
Polk328958
McLeod325745
Morrison312145
Beltrami311048
Lyon302538
Becker286239
Itasca285243
Isanti282941
Carlton280943
Steele27489
Pine267013
Freeborn247923
Todd232230
Nicollet225436
Brown215534
Mille Lacs214545
Le Sueur210715
Cass207723
Meeker200033
Waseca190116
Wabasha17243
Martin170826
Roseau165717
Hubbard149538
Redwood139827
Renville137540
Houston137213
Dodge13544
Chippewa131632
Cottonwood127718
Fillmore12435
Wadena120117
Rock110312
Sibley10857
Aitkin108333
Faribault106716
Watonwan10678
Pennington99715
Kanabec98018
Pipestone94723
Yellow Medicine93715
Murray8935
Jackson86010
Swift83518
Pope7415
Marshall70315
Stevens7018
Clearwater68514
Lac qui Parle65716
Lake64915
Wilkin6269
Koochiching59710
Lincoln4871
Big Stone4603
Unassigned43668
Grant4298
Norman4248
Mahnomen4107
Kittson37220
Red Lake3174
Traverse2523
Lake of the Woods1951
Cook1150

Iowa Coronavirus Cases

Data is updated nightly.

Cases: 307088

Reported Deaths: 4340
CountyCasesDeaths
Polk46016457
Linn17864278
Scott15566166
Black Hawk13875238
Woodbury13040177
Johnson1216051
Dubuque11434153
Pottawattamie9047113
Dallas896572
Story871235
Webster470172
Cerro Gordo467871
Sioux456157
Clinton451863
Warren449038
Marshall428662
Buena Vista393829
Muscatine392278
Des Moines383641
Plymouth351468
Wapello346598
Jasper324059
Lee318131
Marion305752
Jones272649
Henry264831
Carroll255934
Bremer246848
Crawford232324
Washington220332
Boone219517
Benton210150
Mahaska195037
Jackson193031
Tama188758
Dickinson186227
Kossuth174844
Delaware174536
Clay169820
Wright165224
Fayette163623
Hamilton160730
Buchanan160423
Winneshiek156919
Harrison156762
Hardin155529
Cedar154219
Clayton151548
Butler149224
Page144915
Floyd139836
Cherokee139227
Mills136916
Lyon135732
Poweshiek133924
Hancock130724
Allamakee129628
Iowa126022
Calhoun12299
Grundy121626
Jefferson121325
Madison12129
Winnebago119729
Mitchell116235
Louisa115430
Cass113942
Chickasaw112212
Sac111115
Emmet110831
Appanoose110740
Union109222
Humboldt105819
Guthrie103424
Shelby103427
Franklin102718
Unassigned9410
Palo Alto90910
Montgomery86423
Keokuk85626
Howard84419
Monroe81319
Clarke7987
Pocahontas77711
Ida74730
Davis69421
Greene6947
Adair69020
Lucas6589
Monona64616
Osceola6419
Worth6133
Taylor5949
Fremont5176
Van Buren49713
Decatur4934
Ringgold44311
Wayne41721
Audubon4158
Adams2973
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