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Single Pfizer vaccine shot provides strong protection for those who've had COVID-19, UK studies suggest

Just one dose of Pfizer/BioNTech's coronavirus vaccine can induce a strong enough immune response in people who have already had Covid-19 that it could prote...

Posted: Feb 26, 2021 5:20 PM
Updated: Feb 26, 2021 5:21 PM

Just one dose of Pfizer/BioNTech's coronavirus vaccine can induce a strong enough immune response in people who have already had COVID-19 that it could protect from future disease, according to two new papers published in the journal The Lancet on Thursday.

In the United States, the vaccine is authorized as two doses taken 21 days apart. To protect against COVID-19, the first dose primes the immune system and the second boosts it.

One of those new papers, led by researchers at the University College London and Public Health England, included data on 51 health care workers in London. Among those workers, 24 previously had Covid-19. All of the health care workers received a first dose of the Pfizer/BioNTech vaccine and then were tested for antibodies 19 to 29 days later.

The researchers found that in those who had a previous natural infection, vaccination increased their antibody levels more than 140-fold. "This increase appears to be at least one order of magnitude greater than reported after a conventional prime-boost vaccine strategy in previously uninfected individuals," the researchers wrote in their paper.

The other paper, from researchers at Imperial College London and other institutions in the United Kingdom, included data on 72 health care workers who were vaccinated in late December. Twenty-one of them had evidence of previous coronavirus infection.

The workers provided blood samples at the time of receiving their first dose and then 21 to 25 days after vaccination. The researchers found that people with previous coronavirus infection appeared to generate stronger immune responses to one dose of vaccine compared with those who had not been previously infected.

Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia, told CNN on Friday that the findings in the two new papers are not surprising.

"What these data show is exactly what you'd expect -- that people who've been naturally infected, who already had developed an immune response to this virus, when they're then given that quote unquote first dose have a booster response," Offit said. "In other words, they're acting as if they're getting the second dose."

But for now, Offit emphasized that people who have previously recovered from Covid-19 are recommended to still get both doses of vaccine when it is their turn.

"You could reasonably ask, 'Well, given that there's a shortage of vaccine, why not make this recommendation that anyone who's been previously infected can reasonably get one dose, period?' I think the reason that that didn't happen was largely programmatic," Offit said.

"If you tried to overlay on the current strategy of getting people vaccinated -- that there was a screening test beforehand to see who had been previously exposed and who hadn't -- that would make it much more difficult to roll this vaccine out. So, people just thought, look, give everybody the vaccine," Offit said. "There's no downside. Worst case to worst, you'll get just booster responses when you're vaccinated if you've already been naturally infected."

Offit added, "If you've never been infected with this virus before, that second dose of mRNA vaccine dramatically boosts your T-cell immunity, dramatically boosts your antibody response, and will no doubt give more complete and longer-lived protection."

It's possible a single dose of coronavirus vaccine might be enough to protect people who have recovered from a bout of Covid-19, Dr. Francis Collins, director of the US National Institutes of Health, said on Thursday.

"It does look as if in those individuals, a single dose, basically it's a booster for them because they already had the infection. They already have some antibodies that may be sufficient and they may not need the second dose," Collins told CNN Chief Medical Correspondent Dr. Sanjay Gupta.

Collins said that the NIH is "trying to collect as much data as possible about that right now."

But, he said that a single dose strategy for everyone could result in unforeseen consequences.

"Are those people who are in between first and second actually sitting ducks for getting infected?" Collins asked. "Is that actually a way that we might encourage more mutations to happen because they're only partly protected? The virus has a chance to live a little longer in their system and pick up some changes."

Collins said that until the data show otherwise, the authorized two doses three to four weeks apart is the regimen that should be followed.

New York Coronavirus Cases

County data is updated nightly.

Cases: 2715335

Reported Deaths: 57428
CountyCasesDeaths
Kings34831910956
Queens32527210405
Suffolk2543343681
Nassau2251823328
Bronx2127096803
New York1763044661
Westchester1478212356
Erie1238012040
Monroe969811248
Richmond922471967
Orange61914944
Onondaga59057816
Rockland55357783
Dutchess37798508
Albany34221411
Oneida32950637
Niagara28469418
Broome28056432
Saratoga24400224
Schenectady19229244
Ulster18957290
Rensselaer17260192
Chautauqua14837191
Oswego14047133
Putnam13091101
Chemung12740174
St. Lawrence12724143
Steuben12372189
Ontario11592119
Jefferson11237105
Wayne10115102
Cattaraugus9898156
Cayuga9653113
Sullivan950090
Genesee8556144
Herkimer8228143
Clinton801747
Fulton7768110
Tompkins735961
Madison7285108
Warren721996
Livingston713276
Montgomery7110162
Washington660678
Tioga629773
Cortland605389
Allegany5929120
Columbia5664113
Chenango550895
Orleans543496
Franklin536526
Otsego532162
Wyoming525265
Greene491189
Delaware434451
Lewis416940
Seneca320067
Essex296437
Schoharie265424
Yates197433
Schuyler191920
Hamilton5113
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