Ongoing trial shows Pfizer Covid-19 vaccine remains highly effective after six months

The ongoing Phase 3 clinical trial of Pfizer/BioNTech's coronavirus vaccine confirms its protection remains high for at least six months after the second dos...

Posted: Apr 1, 2021 9:32 AM
Updated: Apr 1, 2021 3:30 PM

The ongoing Phase 3 clinical trial of Pfizer/BioNTech's coronavirus vaccine confirms its protection remains high for at least six months after the second dose, the companies said Thursday.

Protection likely lasts even longer than that, vaccine experts say, but they say having data showing good protection six months after people were vaccinated is good news.

The vaccine remains more than 91% effective against disease with any symptoms for six months, the companies said in a statement. And it appeared to be fully effective against the worrying B.1.351 variant of the virus, which is the dominant strain circulating in South Africa and which researchers feared had evolved to evade the protection of vaccines, the companies said.

'The vaccine was 100% effective against severe disease as defined by the U.S. Centers for Disease Control and Prevention (CDC), and 95.3% effective against severe COVID-19 as defined by the U.S. Food and Drug Administration (FDA),' Pfizer and BioNTech said in a joint statement.

The findings indicate protection will last even longer than six months, vaccine experts said.

'The information coming from Pfizer-BioNTech is good news with evidence that those enrolled in the clinical trials last year are still protected. So we know that immunity will not be short-lived,' Dr. Peter Hotez, a vaccine expert and dean of the school of tropical medicine at Baylor College of Medicine, told CNN.

'Hopefully the protection might last years, but we won't know until we know.'

On Wednesday, the companies said a small trial of volunteers aged 12 to 15 showed 100% efficacy in that age group.

'These data confirm the favorable efficacy and safety profile of our vaccine and position us to submit a Biologics License Application to the U.S. FDA,' Albert Bourla, Pfizer's chairman and chief executive officer, said in a statement. A BLA is an application for full approval. The vaccine currently has emergency use authorization, EUA, which falls short of full approval.

'The high vaccine efficacy observed through up to six months following a second dose and against the variant prevalent in South Africa provides further confidence in our vaccine's overall effectiveness.'

Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases, agreed that protection from these vaccines is likely to last longer than six months.

'They know at six months it's clearly there. It more than likely will be even longer. Time will tell,' Fauci told CNN.

Studies of people's immune responses after being vaccinated against coronavirus show they produce high levels of antibodies and then, after a few weeks, the body produces immune cells, known as B cells, that continue to produce fresh protective antibodies, Fauci noted. That makes for lasting immune protection.

Pfizer has been studying the vaccine in more than 46,000 volunteers and has noted 927 cases of confirmed Covid-19.

'From the 927 confirmed symptomatic cases of COVID-19 in the trial, 850 cases of COVID-19 were in the placebo group and 77 cases were in the BNT162b2 group, corresponding to vaccine efficacy of 91.3%,' it said.

'In South Africa, where the B.1.351 lineage is prevalent and 800 participants were enrolled, nine cases of COVID-19 were observed, all in the placebo group, indicating vaccine efficacy of 100%,' the company said.

'Vaccine safety has now been evaluated in more than 44,000 participants aged 16 years and older with more than 12,000 vaccinated participants having at least six months of follow-up after their second dose.'

Dr. Scott Hensley, an immunologist at the University of Pennsylvania who has studied mRNA vaccines like Pfizer's and Moderna's for years, says the strong protection after six months means the vaccines are likely to protect people for even longer -- years, possibly.

'The vaccine elicits such high levels of antibodies that even when confronted with a variant ... there's still meaningful protection,' Hensley told CNN.

'These mRNA vaccines -- it really seems the level of antibodies they elicit are so high, they are persistent. And the combination of having very high levels of antibodies and persistent levels of protection are the recipe for a very long level of protection against these variants,' Hensley added.

'I would not be surprised if this is a vaccine that we only get once.'

Both Pfizer and Moderna use a technology called messenger RNA or mRNA delivery as the basis of their vaccines. The approach has been tested against other viruses and studies in animals and people show they stimulate a strong and broad immune response.

The companies have received emergency use authorization from the US Food and Drug Administration and Pfizer says it will now seek full approval. As part of the process, they both must continue their clinical trials for two years and will continue to report safety and efficacy data as they get it.

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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