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: 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
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