Mayo Dr. speaks on understanding herd immunity

Dr. Gregory Poland, a Mayo Clinic infectious diseases expert and director of the Vaccine Research Group, explains the idea behind herd immunity.

Posted: May 4, 2020 1:29 PM
Updated: May 4, 2020 4:15 PM

ROCHESTER, Minn. - The concept of herd immunity, or community immunity, has sparked debate about whether it would control the spread of COIVD-19. According to the Centers for Disease Control and Prevention (CDC), herd immunity is a situation in which sufficient proportions of a population are immune to an infectious disease to make its spread from person to person unlikely.

"Herd immunity basically means, if you could envision a circle, let's say, of 100 people inside this circle and if you can imagine the susceptible people being in the center of that, the more immune people around the susceptible people, the less likely is it that the virus can penetrate in and actually infect somebody," says Dr. Poland.

Acquiring herd immunity can happen with two approaches, and can come with a deadly cost, according to Dr. Poland.

"There are really only two ways. (The first is) you become immune because you got infected. In the context of COVID-19 that means you have to be willing to accept a lot of severe illnesses and even deaths to get there," he explains. "You've seen some countries do this and say, 'No restrictions, we're going to go for herd immunity.' In some countries, for example, some of them have done that and they've had very high death rates compared to countries that didn’t."

"Or you have a strategy like a vaccine, where you can make somebody immune by tricking the body into thinking it has seen the virus, make antibodies and that antibody be protective," says Dr. Poland.

Dr. Poland says the consequence of going the latter route and implementing social distancing practices means waiting for a vaccine to be developed.

"That means we have lower number of cases, but we push them out longer and slower so we don't overwhelm the medical system. And at some point we have therapies or a vaccine and overall reduce the burden of infection," says Dr. Poland.

The next big question tends to be how much herd immunity is needed to effectively control the spread of COVID-19? Dr. Poland says that's not yet known.

"We know with influenza we need somewhere around 60% of the population to be immune to have herd protection, with measles it's about 95%. The novel coronavirus is probably going to fall into the neighborhood of 70% or so," says Dr. Poland.

Minnesota Coronavirus Cases

Data is updated nightly.

Cases: 697182

Reported Deaths: 8169
CountyCasesDeaths
Hennepin1427711862
Ramsey59431953
Dakota53075503
Anoka48987486
Washington31228315
Stearns25428242
St. Louis20900339
Scott20039146
Wright18954165
Olmsted16269112
Sherburne13840106
Carver1237052
Clay936897
Rice9278125
Blue Earth888747
Crow Wing8070102
Kandiyohi753292
Chisago733858
Otter Tail689897
Benton6653102
Mower576238
Winona564852
Goodhue560581
Douglas549484
Beltrami534672
Itasca532572
Steele520221
McLeod519665
Isanti500470
Morrison478263
Nobles455650
Becker455060
Polk444575
Freeborn438142
Lyon402454
Carlton399160
Nicollet387848
Pine384026
Mille Lacs363860
Brown358244
Cass355536
Le Sueur348230
Todd333034
Meeker314049
Waseca297626
Martin271633
Wabasha25005
Dodge24865
Hubbard241941
Roseau238224
Houston211217
Redwood206642
Fillmore204510
Renville204248
Pennington196022
Wadena192927
Faribault184925
Sibley180310
Cottonwood179424
Chippewa173439
Kanabec168329
Aitkin159239
Watonwan157211
Rock142919
Jackson136112
Pope13378
Yellow Medicine128720
Pipestone126126
Koochiching125119
Swift120319
Murray117610
Stevens110011
Clearwater109218
Marshall107619
Lake94321
Wilkin91014
Lac qui Parle89424
Mahnomen7339
Big Stone7024
Grant6938
Norman6829
Lincoln6724
Kittson54222
Unassigned52893
Red Lake5067
Traverse4375
Lake of the Woods4204
Cook2150

Iowa Coronavirus Cases

Data is updated nightly.

Cases: 443535

Reported Deaths: 6420
CountyCasesDeaths
Polk69441683
Linn26618363
Scott23312265
Black Hawk19397338
Woodbury17483233
Johnson1698692
Dubuque14775221
Pottawattamie13369186
Dallas13048102
Story1211448
Warren707893
Webster6479103
Cerro Gordo6370105
Clinton635898
Des Moines618084
Muscatine5985109
Marshall586981
Sioux547676
Jasper532076
Lee529084
Wapello5230128
Unassigned50150
Buena Vista479442
Marion464086
Plymouth442185
Henry351341
Jones341159
Bremer331365
Washington330454
Crawford326844
Carroll326553
Benton325756
Boone318636
Mahaska282754
Dickinson276547
Kossuth257471
Clay255629
Jackson253844
Tama246073
Hardin244547
Buchanan244238
Delaware240143
Cedar228025
Fayette227945
Page225724
Wright221741
Winneshiek219237
Hamilton216752
Harrison205476
Madison199920
Clayton199758
Floyd195742
Butler191936
Poweshiek188837
Mills188225
Iowa185927
Cherokee184740
Allamakee181152
Jefferson178238
Lyon178041
Calhoun172213
Hancock170336
Winnebago170131
Cass164356
Louisa161651
Grundy161335
Appanoose158149
Shelby156539
Emmet153241
Franklin152224
Humboldt151626
Union149937
Sac147922
Mitchell146143
Guthrie142132
Chickasaw141618
Palo Alto134527
Clarke130226
Montgomery127940
Keokuk121332
Monroe118733
Howard118422
Ida109838
Davis105025
Greene103012
Pocahontas102623
Monona99034
Lucas98523
Adair97734
Worth9558
Osceola84717
Decatur76710
Fremont76511
Van Buren75221
Taylor73412
Wayne66323
Ringgold63027
Audubon60114
Adams4254
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