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How long will coronavirus vaccines protect people?

Ian Haydon helped test Moderna's coronavirus vaccine last year. Now, he's helping test the tweaked version of that vaccine designed to fight a new, more cont...

Posted: Apr 5, 2021 9:06 AM

Ian Haydon helped test Moderna's coronavirus vaccine last year. Now, he's helping test the tweaked version of that vaccine designed to fight a new, more contagious variant.

"A year ago I tried the Moderna vaccine to see if it was safe. (Spoiler: It is!) Now, on my #COVIDvaccine anniversary, I'm happy to share that I just got a 3rd dose. This booster experiment will reveal (1) if strain-adapted vaccines boost immunity & (2) whether they are safe," Haydon, a communications specialist at the University of Washington, said via Twitter last Saturday.

"It's unclear whether this new tweaked version is even going to be necessary," Haydon told CNN in a telephone interview.

"But it's being developed and tested now so that we have it in hand."

Doctors are worried that coronavirus may end up being like influenza, which requires a new vaccine every year both because the circulating strains mutate fast and because immunity from the vaccine wears off quickly.

Although initial evidence suggests immunity from vaccination against coronavirus provides long-lasting protection, vaccine makers have begun making and testing versions of their vaccines that protect against worrying variants of the virus. That includes the B.1.351 version first seen in South Africa, which carries a mutation that, in lab experiments, appears to allow it to evade the human immune response a little.

The latest report from vaccine maker Pfizer shows people in South Africa who got its coronavirus vaccine after B.1.351 became the dominant circulating virus were still very strongly protected from infection -- something that backs up laboratory experiments that have shown the vaccine causes such a strong and broad immune response that it provides a cushion against any effects of mutant viruses.

"It is still matched enough that we have good protection," said Scott Hensley, an immunologist and vaccine expert at the University of Pennsylvania.

But vaccine makers are not taking chances. The trial Haydon is taking part in is testing not only a third dose of Moderna vaccine tweaked to protect specifically against B.1.351 -- that's what he got -- but a third dose of original vaccine in some volunteers, too, to see if the boosted immune response is both safe and provides an advantage.

A report out last month from Pfizer suggests people who get both doses keep strong immunity for at least six months. Experts have been at pains to point out that doesn't mean immunity stops at six months. It means that's the longest volunteers in the trials have been followed to see what their immunity is. It's likely to last much longer, Hensley said.

"I would not be surprised if we learned a year from now that these vaccines are still producing a strong immune response," Hensley told CNN.

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

That would make the vaccine more akin to vaccines against measles than flu vaccines. Vaccination against measles protects against infection for life in 96% of people.

Protection from Pfizer's two-dose vaccine remains above 91% even at six months, according to the company. It has released the details in a statement, not a formal scientific publication, and the data covers only a few thousand people. But if it holds up, that's an indication that both the Pfizer and Moderna vaccines elicit a long-lasting immune response, experts say.

Hensley says the technology used by both vaccines -- delivery of genetic material known as messenger RNA of mRNA -- is especially potent.

"The antibody responses elicited by these mRNA vaccines are incredibly high. What we know in animal models with other mRNA vaccines that have been tested previously -- we know that those antibody responses are incredibly long-lived and they don't drop over time," said Hensley, whose lab has been testing experimental mRNA vaccines for years.

While the coronavirus vaccines are of course new -- the virus has only been around since the end of 2019 -- the mRNA technology has been studied for many years and used to make vaccines against influenza, Ebola and Zika virus.

Several studies have indicated this with coronavirus vaccine.

In January, a team led by Dr. Alicia Widge at the National Institute of Allergy and Infectious Diseases wrote the New England Journal of Medicine to say their research showed two doses of Moderna's vaccine produced plenty of antibodies that declined only very slightly over time. The vaccine also caused the body to produce immune cells known as T cells and B cells that can keep defenses going for years. The vaccine-induced immune response was stronger and less variable than the immune response that follows a natural infection, they found.

Another study in the New England Journal of Medicine in February showed blood taken from people who got Pfizer/BioNTech's Covid-19 vaccine continued to produce an immune response against B.1.351.

"Although we do not yet know exactly what level of neutralization is required for protection against Covid-19 disease or infection, our experience with other vaccines tells us that it is likely that the Pfizer vaccine offers relatively good protection against this new variant," Scott Weaver, director of the Institute for Human Infections and Immunity at University of Texas Medical Branch, told CNN at the time.

Nonetheless, last month, South African virologists argued that there's growing evidence the vaccines being developed do not work as well against B.1.351 and urged vaccine makes to start tweaking their formulas now.

Although he's taking part in clinical trials that require regular blood draws to check his immunity, Haydon has no idea how well protected he is from the virus.

"I know that early on in the trial, myself and all the participants did develop neutralizing antibodies -- the kind that you are looking for. That was clear many, many months ago," Haydon said. "But the level of those antibodies, and how the levels have changed over time, is not something that I'm told. That is one of the main things that is being evaluated over the study."

He had a strong reaction to the first round of vaccination and said the third dose he just received caused some effects, too.

"Flulike is the right way to describe my symptoms," he said. "I ended up with a fever, chills, a little bit of nausea, headache," he added.

Immunologists say that's a sign the immune system is responding to the vaccine, although people who report no symptoms also develop an immune response, so the symptoms do not appear to suggest someone's having a better response than someone who doesn't develop a fever.

Haydon doesn't know whether his response this time around says anything about what level of immunity he still had from the first dose he was given a year ago.

What he does know is that he cannot behave as if he is completely immune. So he still wears a mask whenever he goes out and has avoided almost all travel.

"We're living in a world where most people aren't vaccinated. The fact that you yourself are vaccinated doesn't change everything for you," Haydon said.

"We still have to take a lot of the same precautions as an unvaccinated person," he added. Although your risk of going to the hospital is greatly diminished, spreading the virus is a major concern. It's not until recently that we started to collect data (showing) that vaccinated people also spread the virus a lot less. So that's a recent discovery and a very good sign."

Indiana Coronavirus Cases

Data is updated nightly.

Cases: 708779

Reported Deaths: 13226
CountyCasesDeaths
Marion966191721
Lake51761946
Allen39224672
Hamilton34549405
St. Joseph34157541
Elkhart27356432
Vanderburgh22081394
Tippecanoe21853212
Porter17935299
Johnson17544374
Hendricks16822310
Clark12697190
Madison12353337
Vigo12219244
Monroe11469166
LaPorte11162204
Delaware10366184
Howard9664211
Kosciusko9134114
Hancock7990139
Bartholomew7893155
Warrick7691155
Floyd7563176
Wayne6906198
Grant6844171
Boone6556100
Morgan6405138
Dubois6085117
Marshall5786108
Dearborn570376
Cass5685102
Henry5579101
Noble542683
Jackson493569
Shelby479495
Lawrence4342118
Gibson429089
Harrison428570
Clinton419753
Montgomery418086
DeKalb411184
Whitley380239
Huntington379880
Miami372865
Knox366689
Steuben365757
Putnam353160
Jasper350946
Wabash347878
Adams338052
Ripley334668
Jefferson313180
White308454
Daviess289499
Wells286481
Decatur279092
Fayette277262
Greene270785
Posey268833
Scott261153
LaGrange253670
Clay253544
Randolph235680
Washington231031
Spencer228031
Jennings225047
Fountain208845
Sullivan207942
Starke204752
Owen192356
Fulton192039
Jay186429
Carroll185920
Perry180736
Orange177853
Rush170724
Vermillion166043
Franklin165635
Tipton161043
Parke144616
Blackford133831
Pike130334
Pulaski113845
Newton104234
Brown100140
Crawford97614
Benton97113
Martin82915
Warren79715
Switzerland7698
Union69910
Ohio55811
Unassigned0408

Ohio Coronavirus Cases

Data is updated nightly.

Cases: 1054807

Reported Deaths: 18991
CountyCasesDeaths
Franklin1225191356
Cuyahoga1074592069
Hamilton783261168
Montgomery50176996
Summit45557909
Lucas40298765
Butler37768570
Stark31513895
Lorain24246473
Warren23910293
Mahoning20946583
Lake20067362
Clermont19459229
Delaware18085130
Licking16149207
Fairfield15757197
Trumbull15627460
Medina14922259
Greene14706236
Clark13660293
Wood12806185
Portage12431196
Allen11352229
Richland11067198
Miami10548214
Muskingum8717127
Wayne8594209
Columbiana8569226
Pickaway8439121
Marion8390135
Tuscarawas8387240
Erie7600154
Hancock6730123
Ross6707146
Geauga6553146
Ashtabula6530165
Scioto6295101
Belmont5634158
Union558447
Lawrence5470102
Jefferson5343147
Huron5314114
Darke5273121
Sandusky5189120
Seneca5139120
Washington5087107
Athens503856
Auglaize476284
Mercer471984
Shelby456590
Knox4397108
Madison423959
Putnam421799
Ashland413488
Fulton410567
Defiance404296
Crawford3883101
Brown386955
Logan374476
Preble371098
Clinton362160
Ottawa357978
Highland347459
Williams328674
Champaign321557
Jackson308551
Guernsey307549
Perry290549
Fayette278048
Morrow275939
Hardin264764
Henry264366
Coshocton259857
Holmes253499
Van Wert239262
Pike233831
Gallia233446
Adams229152
Wyandot227553
Hocking209759
Carroll189447
Paulding168838
Meigs141738
Noble132937
Monroe128941
Morgan106823
Harrison105636
Vinton81614
Unassigned02
Fort Wayne
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Angola
Cloudy
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Huntington
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Feels Like: 30°
Fort Wayne
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Lima
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Significantly cold air settles in across northeast Indiana and northwest Ohio Tuesday night.
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