Two doses of Pfizer and Moderna's Covid-19 vaccine are necessary, officials say, but questions still linger

The United States is holding firm to the strategy to administer two doses of the Moderna and Pfizer/BioNTech Covid-19 vaccines a few weeks apart.

Posted: Mar 4, 2021 10:40 AM
Updated: Mar 4, 2021 12:19 PM

The United States is holding firm to the strategy to administer two doses of the Moderna and Pfizer/BioNTech Covid-19 vaccines a few weeks apart.

Still, the idea of expanding the supply by dispensing only one dose hasn't faded away.


FOX 55: Tracking the COVID-19 Vaccine

The Trump administration's surgeon general, Dr. Jerome Adams, said in a tweet on Tuesday that the good protection available with one shot "is better than great protection for a few."

He later clarified with a second tweet that he wasn't recommending that it was 100% the way to go, but that it was worth "giving states the flexibility to try it."

Although 80.5 million vaccine doses have been administered in the United States and the single-dose Johnson & Johnson vaccine is entering the US supply, demand still far outpaces the number of vaccines available.

That has not swayed vaccine makers, the US Food and Drug Administration or the CDC to shift toward single doses to cover more people sooner.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN's Erin Burnett on Wednesday that Adams' tweets were not accounting for the impact of virus variants, which can decrease the amount of protection from vaccines.

"First of all, I love Jerome Adams. He's really a terrific guy. We worked so well together during the Trump administration," Fauci said. "I think he's incorrect on this."

By going with just one dose, "you're at a very tenuous level. Good enough to do protection, but if you diminish it by fivefold, you fall off the chart of protection."

The mRNA vaccines were authorized for use in the US based on clinical trial data that shows two doses of the vaccines taken a few weeks apart are about 95% effective at preventing symptomatic infection. Clinical trials for both vaccines show that the second dose gives a big boost to protective antibodies.

CDC guidelines continue to advise two doses of the Pfizer and Moderna vaccines, and experts at the CDC's Advisory Committee on Immunization Practices (ACIP) meeting on Monday said there's insufficient scientific evidence to support a vaccination strategy that would delay a second dose or eliminate it all together.

"Five studies have shown that postponing the second mRNA dose may leave some people less protected against the SARS-Cov-2 variants," the CDC's Dr. Heather Scobie said at the ACIP meeting.

Fauci told The Washington Post this week there are "risks on either side" of switching to a single dose or sticking with the two.

Experts worry that a single dose strategy could lead to more coronavirus variants, and create more doubt and confusion during an already complicated vaccine rollout.

"We're telling people [two shots] is what you should do ... and then we say, 'Oops, we changed our mind'?" Fauci said. "I think that would be a messaging challenge, to say the least."

That doesn't mean there won't be more dosing changes to come.

Around the world, researchers are looking into the efficacy of single doses of mRNA vaccines. Meanwhile, the J&J vaccine -- currently authorized as a single-dose vaccine -- is also being trialed as two doses to see if it will provide more protection.

Studying single doses

Some countries are already employing single-dose strategies as a way to stretch their supply and offer some protection to more people.

Since late December, the UK has not told people to skip the second shot, but it has delayed the second doses of the Pfizer/BioNTech vaccine to prioritize first doses. The delay meant that the interval between doses could be extended up to 12 weeks instead of about three.

In reaction to the vaccine schedule change, Pfizer said at the time that it did not test its vaccine this way.

"Pfizer and BioNTech's Phase 3 study for the Covid-19 vaccine was designed to evaluate the vaccine's safety and efficacy following a 2-dose schedule, separated by 21 days," Pfizer said. "There are no data to demonstrate that protection after the first dose is sustained after 21 days."

There has been some research that suggests the Pfizer/BioNTech vaccine provides some protection after one dose.

Researchers at Israel's largest hospital looked at what happened after 7,000 staff got vaccinated with the first dose of the Pfizer/BioNTech vaccine. By the second to fourth week after they got the first shot, rates of symptomatic infection were down by 85%.

However, it's still not clear how long this protection would last. Also, the study noted the people who were vaccinated were "younger and healthier" and may not reflect the broader population.

There's some research, too, that suggests one dose might be enough for people with a previous infection. Two papers published last week in The Lancet found that just one dose of Pfizer/BioNTech's coronavirus vaccine can induce a strong enough immune response in people who have already had the coronavirus that it could protect from future infection. France has already recommended that people previously infection get only one dose.

A
nd in a letter sent to the New England Journal of Medicine in February, Canadian researchers went through the documents Pfizer/BioNTech submitted for the emergency use authorization last year and concluded that a single dose is still at least 90% effective.

"With such a highly protective first dose, the benefits derived from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are offered at least one dose," they added.

But, they noted it's still unclear how long protection lasts with just one dose.

Indiana Coronavirus Cases

Data is updated nightly.

Cases: 704632

Reported Deaths: 13211
CountyCasesDeaths
Marion961411718
Lake51322943
Allen39040670
Hamilton34368405
St. Joseph33865539
Elkhart27197431
Vanderburgh22050394
Tippecanoe21725212
Johnson17475374
Porter17240298
Hendricks16754310
Clark12663190
Madison12321337
Vigo12172244
Monroe11417166
LaPorte10841204
Delaware10325184
Howard9629211
Kosciusko9098113
Hancock7954139
Bartholomew7867155
Warrick7680155
Floyd7543176
Wayne6887198
Grant6773171
Boone6524100
Morgan6379138
Dubois6074117
Marshall5770108
Dearborn568576
Cass5678102
Henry5569100
Noble539383
Jackson492869
Shelby478295
Lawrence4336118
Gibson427789
Harrison427570
Clinton417753
Montgomery417286
DeKalb407984
Huntington377480
Whitley376339
Miami371765
Knox365789
Steuben363357
Putnam352360
Jasper347546
Wabash347377
Adams337852
Ripley333468
Jefferson312180
White307854
Daviess289399
Wells285581
Decatur278592
Fayette277162
Greene270485
Posey268433
Scott260853
Clay253044
LaGrange252170
Randolph234680
Washington230631
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Jennings224747
Fountain208245
Sullivan207542
Starke202652
Owen191956
Fulton190939
Jay185829
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Perry179736
Orange176753
Rush170624
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Franklin165635
Tipton160943
Parke144316
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Pike130234
Pulaski113245
Newton103034
Brown99740
Crawford97514
Benton96413
Martin82515
Warren79315
Switzerland7698
Union69710
Ohio55711
Unassigned0408

Ohio Coronavirus Cases

Data is updated nightly.

Cases: 1050112

Reported Deaths: 18991
CountyCasesDeaths
Franklin1219281356
Cuyahoga1067232069
Hamilton780741168
Montgomery49976996
Summit45252909
Lucas39984765
Butler37678570
Stark31385895
Lorain24111473
Warren23864293
Mahoning20869583
Lake19963362
Clermont19423229
Delaware18002130
Licking16109207
Fairfield15676197
Trumbull15553460
Medina14839259
Greene14643236
Clark13602293
Wood12733185
Portage12353196
Allen11312229
Richland11025198
Miami10525214
Muskingum8702127
Wayne8556209
Columbiana8535226
Pickaway8429121
Tuscarawas8370240
Marion8365135
Erie7554154
Hancock6694123
Ross6693146
Geauga6532146
Ashtabula6470165
Scioto6286101
Belmont5610158
Union557447
Lawrence5465102
Jefferson5303147
Huron5298114
Darke5268121
Sandusky5171120
Seneca5108120
Washington5073107
Athens500656
Auglaize475184
Mercer471184
Shelby455890
Knox4380108
Madison421559
Putnam420799
Ashland412688
Fulton409167
Defiance400896
Crawford3866101
Brown386055
Logan372876
Preble369898
Clinton360560
Ottawa356578
Highland346359
Williams324974
Champaign319257
Jackson307951
Guernsey306149
Perry289649
Fayette277348
Morrow274639
Hardin264164
Henry263566
Coshocton258857
Holmes253099
Van Wert238862
Gallia233346
Pike232931
Adams227852
Wyandot226953
Hocking208959
Carroll189147
Paulding168638
Meigs141538
Noble132837
Monroe128841
Morgan106623
Harrison105236
Vinton81414
Unassigned02
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