Why do some people get side effects after COVID-19 vaccines?

Temporary side effects after COVID-19 vaccines are normal and a sign your immune system is revving up.

Posted: Jun 14, 2021 5:02 PM

Why do some people get side effects after COVID-19 vaccines?

Temporary side effects including headache, fatigue and fever are signs the immune system is revving up -- a normal response to vaccines. And they’re common.

“The day after getting these vaccines, I wouldn’t plan anything that was strenuous physical activity,” said Dr. Peter Marks, the U.S. Food and Drug Administration’s vaccine chief, who experienced fatigue after his first dose.

Here's what’s happening: The immune system has two main arms, and the first kicks in as soon as the body detects a foreign intruder. White blood cells swarm to the site, prompting inflammation that’s responsible for chills, soreness, fatigue and other side effects.

This rapid-response step of your immune system tends to wane with age, one reason younger people report side effects more often than older adults. Also, some vaccines simply elicit more reactions than others.

That said, everyone reacts differently. If you didn’t feel anything a day or two after either dose, that doesn’t mean the vaccine isn't working.

Behind the scenes, the shots also set in motion the second part of your immune system, which will provide the real protection from the virus by producing antibodies.

Another nuisance side effect: As the immune system activates, it also sometimes causes temporary swelling in lymph nodes, such as those under the arm. Women are encouraged to schedule routine mammograms ahead of COVID-19 vaccination to avoid a swollen node being mistaken for cancer.

Not all side effects are routine. But after hundreds of millions of vaccine doses administered around the world — and intense safety monitoring — few serious risks have been identified. A tiny percentage of people who got vaccines made by AstraZeneca and Johnson & Johnson reported an unusual type of blood clot. Some countries reserved those shots for older adults but regulatory authorities say the benefits of offering them still outweigh the risks.

People also occasionally have serious allergic reactions. That's why you're asked to stick around for about 15 minutes after getting any type of COVID-19 vaccine — to ensure any reaction can be promptly treated.

Finally, authorities are trying to determine whether temporary heart inflammation that can occur with many types of infections also might be a rare side effect after the mRNA vaccines, the kind made by Pfizer and Moderna. U.S. health officials can't yet tell if there's a link but say they're monitoring a small number of reports, mostly male teens or young adults.

Mississippi Coronavirus Cases

Data is updated nightly.

Cases: 500709

Reported Deaths: 9977
CountyCasesDeaths
Harrison34312538
DeSoto32080403
Hinds31924627
Jackson24482379
Rankin21983390
Lee15530235
Madison14574280
Jones13838242
Forrest13447251
Lauderdale11985316
Lowndes11030188
Lamar10508135
Pearl River9503237
Lafayette8547139
Hancock7728126
Washington7422157
Oktibbeha7142131
Monroe6769176
Warren6682176
Pontotoc6659102
Neshoba6635206
Panola6520131
Marshall6462134
Bolivar6313148
Union602494
Pike5817152
Alcorn5667101
Lincoln5433135
George496779
Scott472698
Tippah469081
Prentiss466881
Leflore4657144
Itawamba4633105
Adams4586119
Tate4584110
Copiah448592
Simpson4445116
Yazoo443987
Wayne439772
Covington428794
Sunflower4237105
Marion4225108
Coahoma4159104
Leake408288
Newton381679
Grenada3706108
Stone359764
Tishomingo359692
Attala331489
Jasper329965
Winston314291
Clay307976
Chickasaw299667
Clarke292494
Calhoun279346
Holmes267887
Smith263850
Yalobusha233747
Tallahatchie227151
Greene219048
Walthall218763
Lawrence212440
Perry205356
Amite205155
Webster202746
Noxubee186640
Montgomery179656
Jefferson Davis171542
Carroll168838
Tunica159439
Benton148738
Kemper141941
Choctaw133426
Claiborne132437
Humphreys129238
Franklin120028
Quitman106428
Wilkinson105139
Jefferson94534
Sharkey64020
Issaquena1937
Unassigned00

Alabama Coronavirus Cases

Cases: 817054

Reported Deaths: 15320
CountyCasesDeaths
Jefferson1145501922
Mobile724601333
Madison52172694
Shelby37533348
Baldwin37192547
Tuscaloosa35044606
Montgomery34067734
Lee23195245
Calhoun22205476
Morgan20754376
Etowah19811497
Marshall18317302
Houston17345411
St. Clair15983339
Cullman15383292
Limestone15298198
Elmore15161284
Lauderdale14225294
Talladega13802276
DeKalb12622260
Walker11162369
Blount10162175
Autauga9954146
Jackson9844182
Coffee9195191
Dale8880185
Colbert8826201
Tallapoosa7071198
Escambia6764130
Covington6699183
Chilton6627161
Russell627959
Franklin5955105
Chambers5567142
Marion4982126
Dallas4936200
Clarke474583
Pike4722105
Geneva4566126
Winston4502103
Lawrence4296117
Bibb424086
Barbour356676
Marengo337789
Monroe331463
Randolph328763
Butler325696
Pickens315682
Henry311965
Hale311088
Cherokee301760
Fayette291879
Washington251351
Cleburne247360
Crenshaw244375
Clay241768
Macon232363
Lamar222047
Conecuh185853
Coosa179739
Lowndes174564
Wilcox167939
Bullock151644
Perry138340
Sumter132738
Greene126644
Choctaw88127
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Clear cool and dry to begin your weekend, but both afternoons should be a little bit above what we expect for this time of year temperature wise. Rain chances begin to return late Sunday night, with at least two chances for storms over the next week, summer could be strong.
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