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: 350070

Reported Deaths: 7590
CountyCasesDeaths
Hinds24512449
DeSoto23513283
Harrison21172335
Rankin15798293
Jackson15735254
Madison11171227
Lee10903180
Jones9223169
Forrest9027163
Lauderdale8087244
Lamar724890
Lowndes7199152
Lafayette6631125
Washington5661140
Pearl River5357154
Oktibbeha503198
Bolivar5004134
Warren4817128
Panola4812112
Marshall4739106
Pontotoc452473
Hancock440388
Neshoba4401181
Union438979
Monroe4369138
Lincoln4228116
Pike3739114
Leflore3676125
Alcorn355374
Tate354988
Sunflower351094
Adams347490
Scott346677
Yazoo342977
Copiah330869
Simpson327191
Itawamba317281
Coahoma315685
Tippah312869
Prentiss302563
Covington302384
Marion289882
Leake288676
Wayne280945
George277351
Grenada272188
Newton266864
Tishomingo240770
Winston238084
Stone235338
Jasper234748
Attala228674
Chickasaw221460
Holmes202574
Clay201954
Clarke189580
Tallahatchie185642
Calhoun183232
Smith183036
Yalobusha173641
Walthall150449
Lawrence145426
Greene141935
Amite139144
Noxubee137235
Perry136138
Montgomery133944
Carroll127031
Webster124332
Jefferson Davis119834
Tunica116127
Benton107825
Claiborne105931
Kemper104429
Humphreys102333
Franklin88424
Quitman86319
Choctaw83119
Wilkinson79332
Jefferson72228
Sharkey51918
Issaquena1746
Unassigned00

Alabama Coronavirus Cases

Cases: 592417

Reported Deaths: 11542
CountyCasesDeaths
Jefferson861091591
Mobile49771865
Madison37714533
Shelby27501259
Tuscaloosa27344465
Montgomery26343628
Baldwin25860329
Lee17336181
Calhoun15498334
Morgan15225291
Etowah15060370
Marshall13198236
Houston12191293
Elmore10977219
St. Clair10852252
Limestone10816158
Cullman10610206
Lauderdale10305254
DeKalb9594192
Talladega9005188
Walker7840288
Autauga7615114
Jackson7431117
Blount7417139
Colbert6752142
Coffee6443132
Dale5723117
Russell482243
Chilton4810117
Covington4804125
Franklin462781
Tallapoosa4571156
Escambia451083
Chambers3987125
Dallas3751163
Clarke372263
Marion3470107
Pike334079
Lawrence3277100
Winston300773
Bibb292865
Geneva288383
Marengo262967
Barbour253761
Pickens247762
Butler242472
Hale236778
Fayette228165
Henry216545
Monroe204541
Randolph202844
Cherokee200748
Washington186839
Macon171552
Crenshaw170658
Clay167159
Cleburne161845
Lamar151938
Lowndes146255
Wilcox132331
Bullock126542
Conecuh122132
Coosa119529
Perry111228
Sumter110633
Greene99337
Choctaw64425
Out of AL00
Unassigned00
Tupelo
Clear
81° wxIcon
Hi: 86° Lo: 64°
Feels Like: 82°
Columbus
Clear
82° wxIcon
Hi: 87° Lo: 64°
Feels Like: 84°
Oxford
Clear
81° wxIcon
Hi: 85° Lo: 61°
Feels Like: 81°
Starkville
Clear
79° wxIcon
Hi: 85° Lo: 63°
Feels Like: 81°
Wednesday starts off in the nice middle 60s, even some towns down into the lower 60s. We will stay with plenty of sunshine as we go through the day. Most of our high temperatures on Wednesday will be well into the 80s to near 90 degrees in the afternoon.
WTVA Radar
WTVA Temperatures
WTVA Severe Weather