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 9:27 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."

Mississippi Coronavirus Cases

Data is updated nightly.

Cases: 314710

Reported Deaths: 7254
CountyCasesDeaths
DeSoto21646260
Hinds20369416
Harrison17949309
Rankin13643278
Jackson13450246
Madison10113217
Lee9986174
Jones8384163
Forrest7689152
Lauderdale7198240
Lowndes6403148
Lamar623686
Lafayette6203119
Washington5341134
Bolivar4802132
Oktibbeha462998
Panola4596107
Pearl River4519146
Marshall4450103
Warren4393121
Pontotoc420872
Monroe4115133
Union411176
Neshoba4031176
Lincoln3969110
Hancock379586
Leflore3498125
Sunflower336290
Tate334784
Pike3327105
Scott316274
Alcorn313368
Yazoo311770
Itawamba300577
Copiah297465
Coahoma295579
Simpson295388
Tippah288768
Adams286982
Prentiss280060
Marion269380
Leake268473
Wayne262841
Grenada261587
Covington259881
George248148
Newton246862
Winston227581
Tishomingo227067
Jasper221148
Attala214473
Chickasaw208057
Holmes189174
Clay185554
Stone182833
Tallahatchie178941
Clarke178080
Calhoun170932
Yalobusha164638
Smith162534
Walthall134245
Greene130633
Lawrence128724
Montgomery127142
Noxubee126734
Perry126338
Amite123142
Carroll121829
Webster114532
Jefferson Davis107133
Tunica105726
Claiborne102430
Benton100025
Humphreys96733
Kemper95828
Franklin83923
Quitman81116
Choctaw76418
Wilkinson67531
Jefferson65728
Sharkey50217
Issaquena1686
Unassigned00

Alabama Coronavirus Cases

Cases: 540083

Reported Deaths: 11038
CountyCasesDeaths
Jefferson798481529
Mobile41283809
Madison35157506
Tuscaloosa25925455
Shelby25302249
Montgomery24723593
Baldwin21411310
Lee15993172
Calhoun14574319
Morgan14425280
Etowah13925353
Marshall12280225
Houston10648282
Elmore10158206
Limestone10070151
St. Clair9948245
Cullman9768194
Lauderdale9460243
DeKalb8865188
Talladega8341176
Walker7261278
Autauga7005108
Jackson6840112
Blount6773139
Colbert6322135
Coffee5581118
Dale4877113
Russell445738
Chilton4373113
Franklin426382
Covington4138118
Tallapoosa4044153
Escambia394877
Chambers3596123
Dallas3569153
Clarke351561
Marion3140101
Pike312077
Lawrence303098
Winston275873
Bibb264764
Geneva254178
Marengo249865
Pickens234862
Barbour232056
Hale224078
Butler219169
Fayette212862
Henry189943
Cherokee184845
Randolph182542
Monroe178141
Washington167839
Macon161350
Clay157257
Crenshaw153557
Cleburne149641
Lamar143336
Lowndes140653
Wilcox127430
Bullock123242
Conecuh110829
Coosa109228
Perry107826
Sumter105032
Greene92634
Choctaw61024
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Columbus
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