CDC study finds Pfizer, Moderna vaccines are 90% effective after two doses in real-world conditions

Under real world conditions, the Pfizer and Moderna Covid-19 vaccines provide highly effective protection, according to a new report from the...

Posted: Mar 29, 2021 4:15 PM
Updated: Mar 29, 2021 11:15 PM

Under real world conditions, the Pfizer and Moderna Covid-19 vaccines provide highly effective protection, according to a new report from the US Centers for Disease Control and Prevention.

At full vaccination, the vaccines were 90% effective at preventing infections, including infections that had no symptoms. At least 14 days after first dose but before second dose, they were 80% protective, according to the agency's Morbidity and Mortality Weekly Report published Monday. The CDC said it is the first of many planned Covid-19 vaccine effectiveness studies.

The study looked at how the vaccines protected nearly 4,000 health care workers and first responders. The volunteers in the study worked in eight locations around the country and had been observed from mid-December to mid-March.

The CDC tested volunteers routinely regardless of symptoms. The CDC also monitored the volunteers through text message, e-mail and direct medical reports. The volunteers also did a nasal swab once a week.

Most of the volunteers, more than 62%, had received both doses of either a Pfizer or Moderna Covid-19 vaccine. More than 12% had received just a single dose.

Among the 2,961 people vaccinated with one or more doses and the 989 unvaccinated participants, a total of 205 had a positive PCR test for Covid-19. One hundred sixty-one infections were identified when participants were unvaccinated; eight were identified among those partially immunized and three were identified among those fully immunized -- more than 14 days after their second dose of vaccine. Thirty-three identified cases were excluded because the person's immune status was not clear.

More than 87% of Covid-19 cases had symptoms. Nearly 23% of the cases sought help from a doctor. There were two hospitalizations, but no deaths.

The results of this study are similar to what scientists saw in clinical trials for the vaccines, but studies like this are important to show how effective the vaccines are, particularly in a population that, through their work, can encounters a large number of people who have Covid-19.

The results showing the level of protection from a single dose after two weeks are similar to findings from other recent studies in the UK and Israel.

'Reducing the risk for transmissible infection, which can occur among persons with asymptomatic infection or among persons several days before symptoms onset, is especially important among health care personnel, first responders, and other essential and frontline workers given their potential to transmit the virus through frequent close contact with patients and the public,' the report concluded.

'This study is tremendously encouraging,' CDC Director Dr. Rochelle Walensky said Monday at the White House Covid-19 briefing. 'These findings also underscore the importance of getting both of the recommended doses of the vaccine in order to get the greatest level of protection against Covid-19, especially as our concerns about variants escalate.'

'Our national vaccination efforts are working,' Walensky added.

The US has made a big push to get people vaccinated. As of Monday, nearly 29% of the US population -- more than 95 million people -- have received at least one dose, and nearly 16% of the population -- about 52.6 million people -- are fully vaccinated, CDC data shows. Among those 18 and older, more than 1 in 5 are fully vaccinated.

'Get vaccinated when you can,' Walensky said. 'So that all those people that we all love will still be here when this pandemic ends.'

Mississippi Coronavirus Cases

Data is updated nightly.

Cases: 501097

Reported Deaths: 9990
CountyCasesDeaths
Harrison34338538
DeSoto32117403
Hinds31939628
Jackson24494382
Rankin21995390
Lee15543235
Madison14581280
Jones13851242
Forrest13453251
Lauderdale11991317
Lowndes11050188
Lamar10521135
Pearl River9533237
Lafayette8550140
Hancock7732127
Washington7438158
Oktibbeha7146131
Monroe6777177
Warren6694176
Pontotoc6664102
Neshoba6637206
Panola6531131
Marshall6467134
Bolivar6317148
Union602894
Pike5820152
Alcorn5669101
Lincoln5436135
George496879
Scott472898
Tippah469281
Prentiss467281
Leflore4658144
Itawamba4636105
Tate4588111
Adams4587119
Copiah448592
Simpson4446116
Yazoo444187
Wayne439772
Covington428894
Sunflower4239105
Marion4226108
Coahoma4160105
Leake408288
Newton381779
Grenada3707108
Stone360364
Tishomingo359792
Attala331589
Jasper329965
Winston314291
Clay308076
Chickasaw300367
Clarke292494
Calhoun279446
Holmes267987
Smith264050
Yalobusha234047
Tallahatchie228051
Greene219348
Walthall218763
Lawrence212940
Perry205556
Amite205156
Webster202946
Noxubee186740
Montgomery179656
Jefferson Davis171743
Carroll169138
Tunica159839
Benton148838
Kemper141941
Choctaw133426
Claiborne132737
Humphreys129538
Franklin120228
Quitman106428
Wilkinson105139
Jefferson94534
Sharkey64120
Issaquena1937
Unassigned00

Alabama Coronavirus Cases

Cases: 819597

Reported Deaths: 15406
CountyCasesDeaths
Jefferson1147901924
Mobile725791338
Madison52306697
Shelby37597350
Baldwin37245552
Tuscaloosa35101612
Montgomery34106740
Lee23526246
Calhoun22225488
Morgan20941378
Etowah19825500
Marshall18361304
Houston17384412
St. Clair16054339
Cullman15443293
Limestone15343199
Elmore15241286
Lauderdale14302295
Talladega13836283
DeKalb12649261
Walker11202370
Blount10192176
Autauga10043148
Jackson9871184
Coffee9210191
Dale8897185
Colbert8860201
Tallapoosa7084198
Escambia6772134
Covington6712183
Chilton6641162
Russell636659
Franklin5959105
Chambers5607142
Marion5005127
Dallas4973200
Pike4795106
Clarke475584
Geneva4571127
Winston4516103
Lawrence4321117
Bibb425186
Barbour357776
Marengo338090
Monroe331464
Randolph329764
Butler326396
Pickens316284
Henry312666
Hale311388
Cherokee302860
Fayette292880
Washington251551
Cleburne247760
Crenshaw245275
Clay243368
Macon234663
Lamar224147
Conecuh186153
Coosa180240
Lowndes175164
Wilcox168839
Bullock151644
Perry138840
Sumter133038
Greene126744
Choctaw88527
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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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