Booster shots aren’t necessary right now, US health agencies say. Pfizer is seeking authorization anyway.

Netherlands Pfizer Vaccine Rollout
A healthcare worker in the Netherlands receives the Pfizer vaccine on January 6, 2021.

  • Fully vaccinated Americans don’t need booster shots right away, US health agencies said on Thursday.
  • Pfizer announced earlier that day that it plans to seek authorization for a booster next month.
  • The spread of the Delta variant has raised concerns about how long vaccine protection lasts.
  • See more stories on Insider’s business page.

Pharmaceutical companies and disease experts increasingly disagree about when booster shots might be necessary.

Pfizer announced Thursday that it plans to seek authorization for a booster shot next month. But in a joint statement later the same day, the Food and Drug Administration and Centers for Disease Control and Prevention said Americans don’t need boosters right away.

Pfizer anticipates that a third dose of its existing coronavirus vaccine could be given six to eight months after the first two, the company’s research head, Mikael Dolsten, told Bloomberg.

But research so far indicates that coronavirus vaccine protection lasts for the better part of a year, and likely many months beyond that.

Still, the spread of the Delta variant – the most transmissible version of the virus to date – has raised concerns about the degree to which vaccine protection holds up, and whether it could fade more quickly. Preliminary data from Israel’s health ministry found that Pfizer’s vaccine was 64% protective against coronavirus infections from June to July, when the Delta variant was spreading widely in the country. The vaccine was 94% effective the prior month, before Delta infections surged.

Dolsten told Bloomberg that these findings indicate antibody levels may have faded among vaccinated people in Israel. That could result in more mild breakthrough cases – the term for COVID-19 diagnoses at least two weeks after someone is fully vaccinated.

But many disease experts say that the goal of vaccines has always been to prevent severe disease and death, which the shots still do in the face of Delta. The Israeli data, along with several other studies, show that Pfizer’s vaccine largely prevents hospitalization. Two doses were 93% effective at keeping people in Israel out of the hospital from June to July, and 98% the month prior.

“People who are fully vaccinated are protected from severe disease and death, including from the variants currently circulating in the country such as Delta,” the CDC and FDA wrote. The statement added that “virtually all COVID-19 hospitalizations and deaths are among those who are unvaccinated.”

Preventing mild cases could still curb the virus’ spread

COVID test texas
A healthcare worker administers a COVID-19 test in Houston, Texas, June 25, 2020.

There are benefits to preventing mild coronavirus cases, of course. Nobody wants to get sick, and scientists still don’t know whether mild breakthrough cases can leave people with long-lasting symptoms the way some natural infections do.

Researchers also increasingly suspect that it might be easier for vaccinated people to spread the Delta variant to others. (Studies done before Delta emerged indicated that Pfizer’s and Moderna’s vaccines helped reduce asymptomatic transmission.)

But the CDC stopped monitoring non-severe COVID-19 cases among vaccinated people in May, making the answers to these questions elusive.

Experts don’t even know for sure yet whether vaccines are significantly less effective in the face of Delta. A recent study found that 95% of blood samples from vaccinated people developed neutralizing antibodies against Delta after two doses of Pfizer’s vaccine – a sign that those people would be protected from a symptomatic infection.

A UK analysis, too, found that Pfizer’s vaccine was 88% effective against symptomatic COVID-19 caused by Delta. And a Canadian study similarly found that Pfizer’s vaccine was 87% effective against symptomatic Delta infections.

However, the same studies indicate that just a single dose of Pfizer’s vaccine was either weakly or not at all effective against Delta.

Drug companies’ approach: ‘Better safe than sorry’

Pfizer CEO Albert Bourla
Pfizer CEO Albert Bourla.

Insider recently spoke with nine experts about booster shots, and several predicted that follow-up doses wouldn’t be necessary for another one to five years. Others questioned whether the general public would ever need another round of shots.

But for the most part, pharmaceutical companies have adopted a “better safe than sorry” approach.

“I think for next fall, we, as a community, should rather be two months too early boosting than two months too late,” Moderna CEO StĂ©phane Bancel said at a Goldman Sachs investor conference in June.

Pfizer’s early data does seem to suggest that boosters could offer additional immune protection: A third shot appears to increase neutralizing antibody levels five-to-10-fold compared to the original vaccine.

But US health agencies are looking for a more holistic picture of how vaccine protection holds up over time, based on laboratory, clinical-trial, and real-world data. Studies from pharmaceutical companies are just one part of that, the CDC and FDA said on Thursday.

Ultimately, the decision to roll out boosters will depend on the level of vaccine efficacy that health authorities are willing to accept – a threshold that hasn’t been determined yet. Research might also still reveal that antibody responses only dip in certain groups of people, such as the elderly, people with preexisting health conditions, or those who never caught the disease. So boosters could wind up being recommended for just a limited group.

“We are prepared for booster doses if and when the science demonstrates that they are needed,” the CDC and FDA said.

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The original coronavirus strain has almost disappeared in the US. One chart shows how variants took over.

covid delta variant
A mobile COVID-19 vaccination center in Bolton, England, on June 9, 2021.

  • Coronavirus variants have largely replaced the original strain, rendering it essentially obsolete.
  • The Alpha variant took over as the US’s dominant strain in April. Delta could replace it soon.
  • Scientists aren’t sure whether more contagious variants will evolve from the dominant ones.
  • See more stories on Insider’s business page.

Viruses will do what it takes to survive – even if it means killing off an older, weaker self and replacing it with a more transmissible strain.

For the first several months of the pandemic, however, the coronavirus had no need to become more dangerous: The virus was doing a good job of spreading, with each new infected person passing it to an average of two to three others. At the time, scientists hoped that the original strain of the virus, known as the “wild type,” was already contagious enough that it wouldn’t evolve further.

But as the pandemic swelled and more people got infected, the coronavirus had more opportunities to replicate, and therefore mutate, incurring small, random changes in its genetic sequence. Most mutations are harmless, but every so often a distinct set yields new properties – a variant.

Scientists now estimate that variants have almost completely replaced the original strain in the US, rendering it essentially obsolete.

“Pretty much all the virus that’s circulating right now has one of these variants that make it differ from the original strain that first took off across the world,” Tyler Starr, a postdoctoral research fellow at the Fred Hutchinson Cancer Research Center, told Insider.

The chart below shows how a few variants have dominated the US since February. More than 200 less prevalent strains, including the original version of the virus, are listed as “other.”

The Alpha variant, first identified in the UK in September, became prevalent in the US from February to April, going from 27% to 70% of all circulating strains. It’s about 50% more transmissible than the original strain, according to the Centers for Disease Control and Prevention. Meanwhile, the share of other coronavirus strains (including the original) fell from 20% to 4%.

By May, Alpha had a strong competitor: Delta. An analysis from Public Health England found that the Delta variant was associated with a 60% increased risk of household transmission compared to Alpha, though more recent estimates suggest that difference is closer to 40%.

From May to June, Delta grew from less than 3% of all circulating strains in the US to more than 20%. It’s poised to become the US’s dominant strain within weeks.

“Basically everywhere, once Delta gets there, it does overtake something like the Alpha variant,” Starr said. “That is evidence that, to some degree, it is more transmissible.”

Could an even more contagious variant replace Delta?

variant lab
Researchers sequence coronavirus samples at the University Hospital of Badajoz in Spain on April 15, 2021.

So far, Starr said, coronavirus variants – even Delta – aren’t fundamentally different from the wild type.

“These mutations might be slightly modifying things like transmissibility,” he said, but “that trait was there in the original virus and it’s just being altered slightly.”

In fact, some scientists wonder if the virus is nearing “peak fitness,” the point after which it no longer mutates to become more infectious.

Delta is by far the “fittest” variant to date, according to the World Health Organization. In addition to being more transmissible than other strains, it may also be deadlier: Researchers in Scotland found that getting infected with Delta doubled the risk of hospital admission relative to Alpha. (Previous studies have suggested that the Alpha variant may be 30 to 70% deadlier than the original strain.) Vaccines, of course, significantly lower that risk for both variants.

“Delta is absolutely going up the fitness peak – whether it’s at the top, I think that’s very hard to say until we just don’t see any further change,” Andrew Read, who studies the evolution of infectious diseases at Pennsylvania State University, recently told Insider.

“If Delta takes over the world and nothing changes,” he added, “then we’ll know in a while – a year or two – that it is the most fit.”

But Starr thinks the virus probably won’t ever stop mutating.

“As people continue to get immunity, the virus will continue to evolve to be able to transmit and infect people,” he said. “But at the same time, we’ll have that low-level immune reaction that makes it a much less severe thing over time.”

It’s still possible that an entirely new lineage might replace Delta as the dominant variant, or that two variants – Delta and Alpha, for instance – could combine mutations to produce an even more infectious strain. In the worst-case scenario, the virus could evolve into a “variant of high consequence” – one that’s far more distinct than the variants currently circulating and highly resistant to vaccines. That hasn’t been observed yet.

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Dr. Fauci explains why COVID-19 vaccines work much better than natural immunity to protect you from the coronavirus

fauci gets his first vaccine
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, gives a thumbs up after receiving his first dose of a COVID-19 vaccine at the National Institutes of Health on December 22, 2020 in Bethesda, Maryland.

  • Dr. Anthony Fauci discussed new data suggesting that COVID-19 vaccines “can do better than nature.”
  • People who’ve had prior infections saw their immune response to COVID-19 drastically improve after receiving mRNA vaccines.
  • The finds are a beacon of hope, as new variants (which may reinfect people) circulate the globe.
  • See more stories on Insider’s business page.

Dr. Anthony Fauci is calling it: mRNA COVID-19 vaccines can provide people with better protection against new viral variants than a prior coronavirus infection alone can.

During a White House COVID-19 briefing on Tuesday, Fauci pointed to several new studies, which, when taken together, suggest that the mRNA vaccines from Pfizer and Moderna provide great immune protection against newly circulating viral variants.

According to the data, the vaccines bump up any natural protection people may have had from prior infection substantially.

“Vaccines, actually, at least with regard to SARS-CoV-2 [the coronavirus] can do better than nature,” Fauci, America’s leading infectious disease expert, said. “Vaccination in people previously infected significantly boosts the immune response.”

Two of the studies that Fauci referenced during the briefing have been peer-reviewed, meaning other independent scientists have given them a thumbs up, while two others are still awaiting peer approval. But they all tell a very similar story.

Four studies all show superior protection against variants from vaccines

One study found that people who’d had two doses of an mRNA coronavirus vaccine (either Pfizer’s or Moderna’s) had antibody titer levels “up to 10 times” that of a natural infection, Fauci said, suggesting those vaccines give people’s bodies more fighting power against viral variants than a prior illness can.

“You had interesting increased protection against the variants of concern,” Fauci said.

Another small study showed that previously infected people who got vaccinated were exceptionally well protected against three of the five major variants of concern: the P1 variant, first identified in Brazil, the B.1.1.7 variant from the UK which is now dominant in the US, and the B.1.351 variant, first found in South Africa.

But that’s not all. In another study that Fauci mentioned, people who’d been previously infected with COVID also displayed better T-cell immunity after a single dose of Pfizer’s mRNA vaccine. (T cells can help make infections milder, if people do ever get reinfected.)

“Now, remember these are only laboratory data, have not been proven in the clinic,” Fauci said, pointing out that the new studies are based on blood tests, so it’s hard to know exactly how everything would play out with real-world infections and variants. “But they are really very interesting, and things that we need to follow up on,” he added.

The final study Fauci cited suggested that people who have recovered from a prior COVID-19 infection who then get vaccinated may receive great broadband protection, not just against concerning viral variants, but also against other coronaviruses, like SARS, from their COVID-19 vaccination. That’s a virus-fighting power that people who’ve been infected but not vaccinated don’t get.

“Vaccines are highly efficacious,” Fauci concluded. “They are better than the traditional response you get from natural infection.”

fauci showed this slide during wednesday's briefing, which has a graph showing better antibody protection against variants in previously infected people after vaccination
Messenger RNA vaccines (mRNA) are standing up to variants really well, so far.

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The research is in: People who’ve already had COVID-19 need just one shot

woman receiving covid vaccine
A woman receiving a COVID-19 vaccine in Wales.

  • A single shot of Pfizer or Moderna’s vaccine yields high protection for people who’ve had COVID-19.
  • That’s probably because their bodies are responding to a viral threat they’ve seen before.
  • One expert said giving people who’ve had COVID-19 a second dose was “kind of a wasted shot.”
  • Visit the Business section of Insider for more stories.

In the race to get coronavirus vaccines into arms as quickly as possible, scientists think they’ve found a way to accelerate the process: Give the people who’ve already had COVID-19 just one dose.

Most vaccine-eligible Americans are getting either Pfizer’s or Moderna‘s vaccine, both of which require two doses administered several weeks apart. But a growing chorus of researchers now agrees that a single dose of either vaccine will generate a sufficient immune response among people who’ve already had the coronavirus. Giving them the second dose, research suggests, might essentially waste a good shot.

“For those who’ve been infected and recovered, which is tens of millions of people, they’ll only need one shot, which will make the vaccine go even further,” Dr. James Hildreth, the president of Meharry Medical College, told Insider.

Hildreth served on the Food and Drug Administration advisory committee that recommended all three authorized coronavirus vaccines in the US. The third, from Johnson & Johnson, is a one-shot vaccine, so people who’ve had COVID-19 would get a single dose of that no matter what.

Given that more than 30 million Americans are known to have had COVID-19, that could be up to 15 million Pfizer or Moderna shots that could go to other people.

New research backs up the one-shot strategy

Once a person has had COVID-19, their immune system should recognize the virus if it invades a second time. So when a vaccine spurs the body to start producing antibodies again, it’s logical that the immune system would mount a stronger and quicker defense.

Indeed, a new peer-reviewed study found similar antibody responses among individuals who’d had COVID-19 and received a single dose of Pfizer’s vaccine and individuals who received two doses of the vaccine but had never gotten COVID-19.

The researchers concluded that “a second vaccine dose did not offer previously infected individuals a substantially greater benefit over a single dose.”

After the first dose, nearly 37% of the study participants who’d had COVID-19 experienced significant side effects versus 25% of study participants who’d never had COVID-19. After the second dose, there wasn’t as much difference between the two groups: 51% versus 59%, respectively.

The researchers found that “fever and chills were more common among previously infected vaccine recipients after the first dose, whereas infection-naive individuals were more likely to experience headache, dizziness, or lightheadedness after the second dose.”

‘The first dose ends up serving as the booster’

Registered Nurse Robert Orallo administers the Pfizer Covid-19 vaccine at the Blood Bank of Alaska in Anchorage on March 19, 2021.

In a letter in the New England Journal of Medicine last month, 32 researchers from the Icahn School of Medicine at Mount Sinai wrote that a single-dose strategy for people who’d already had the virus “requires investigation.”

The team found in a small study that people who’d previously had COVID-19 developed 10 to 45 times as many antibodies after their first dose of Pfizer or Moderna’s vaccine as the average uninfected person did. The research is still awaiting peer review.

“The first dose ends up serving as the booster,” Dr. Jeremy Faust, an emergency-medicine physician at Brigham and Women’s hospital, told Insider. “If you’ve been infected, it’s very likely that one dose would be pretty damn good for quite a while.”

There are a few caveats, though: People may need to confirm that they still have antibodies if they were sick a while ago, since antibody levels wane over time. An antibody test would also be required for those who suspect they had COVID-19 but never tested positive. If that antibody test comes back positive, the second shot is most likely redundant.

“What is the point?” Akiko Iwasaki, an immunobiologist at Yale University, told Insider. “It’s kind of a wasted shot.”

‘This is where the policy lags science’

UK testing antibody
A paramedic with a blood sample for a COVID-19 testing program in June.

France in February began recommending a single vaccine dose for people who’ve had COVID-19.

By then, the Mount Sinai research was out, and another preliminary study had also discovered high antibody levels among healthcare workers who’d had COVID-19 before receiving their first shot.

Dr. Mohammad Sajadi, a coauthor of that study, told Insider that COVID-19 patients typically develop antibodies about two to three weeks after their initial infection. But the healthcare workers showed high antibody levels a week after their first shot.

“What that shows you is that individuals who had a prior COVID infection have what we call a recall response or a memory response,” Sajadi said. “For most infections, the second time you see that microorganism, you should get a faster response.”

Then in late February, a UK study found roughly equal antibody levels among people who’d received the first dose of Pfizer’s vaccine and had never gotten COVID-19 and those who’d had COVID-19 but weren’t vaccinated yet. After the people who’d had COVID-19 got their first shot, their antibody levels were 140 times their peak levels before the vaccine.

Yet most countries, including the US, don’t yet recommend a single-dose regimen for people who’ve had COVID-19.

“This is where the policy lags science,” Iwasaki said.

Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, told NBC News in February that the idea was worth considering.

“The data looked really quite impressive – that if you’ve been infected and then you get a single dose, the boost that you get with that single dose is really enormous,” Fauci said. “That is one thing that you might want to consider, but we really want to look carefully at the data first.”

Concerns about long-term immunity

covid vaccine card cdc
An intensive-care-unit nurse, Megan Tschacher, with her vaccination card at UC Health Poudre Valley Hospital in Fort Collins, Colorado, on December 14.

Since scientists haven’t had much time to follow up with vaccine recipients, there’s no consensus yet about how long vaccine-induced immunity lasts. This uncertainty is one reason experts are hesitant to advocate anything other than the standard two-dose regimens of the Pfizer and Moderna vaccines.

Delaying or skipping the second dose places a lot of pressure on the first dose to provide solid, long-term immune protection, Princeton University researchers wrote Tuesday. They expressed concern that switching up the dosing regimen could lead to a “broad range” of outcomes among vaccinated people.

But Iwasaki said people who’d had COVID-19 could probably wait months before getting their second shot – if they need one at all.

“There just isn’t any need to do it so early,” she said.

Scientists are also optimistic that even though antibody levels are known to wane over time, T cells will confer long-term protection for those who’ve had COVID-19. Like antibodies, T cells have impressive powers of recollection that can help the immune system recognize and reattack the coronavirus.

A recent study found that people who previously had COVID-19 mounted a stronger T-cell response to one shot of Pfizer’s vaccine than people who’d never gotten infected did.

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Elon Musk set up a COVID-19 antibody study at SpaceX and got 4,300 employees to take part, according to reports

elon musk space x SpaceX Chief Engineer Elon Musk speaks in front of Crew Dragon cleanroom at SpaceX Headquarters in Hawthorne, California on October 10, 2019. (Photo by Yichuan Cao/NurPhoto via Getty Images)
SpaceX CEO Elon Musk.

  • Elon Musk’s company SpaceX has been regularly testing a group of employees for COVID-19 antibodies.
  • 4,300 employees signed up for a study looking at possible links between antibodies and immunity.
  • “People can have antibodies, but it doesn’t mean they are going to be immune,” said one of the study’s authors.
  • Visit the Business section of Insider for more stories.

Elon Musk’s space exploration company SpaceX has been using its employees to run a COVID-19 antibody study, The Wall Street Journal reported Saturday.

The results of the study were made public in a peer-reviewed paper published in Nature Communications, which lists Elon Musk as a co-author.

According to the study, SpaceX sent an email round to staff asking for volunteers to participate in a regular antibody study to study COVID-19. After that email was sent, 4,300 SpaceX employees signed up to give monthly blood samples so they could be tested for antibodies.

According to the Journal, Musk and SpaceX’s top medical executive Anil Menon worked to bring on various doctors and academics to design the study.

The published study includes data spanning from April – when the testing  started – and June, although regular testing is still ongoing according to the Journal.

The study provides more information in the ongoing efforts to understand how COVID-19 works, and whether a certain number of antibodies could provide a level of immunity.

The study’s findings suggest that people who had only mild COVID-19 symptoms developed fewer antibodies, which might mean they are less likely to have long-term immunity and could therefore get reinfected.

Researchers still working on the study told the Journal they have already observed some instances of reinfection in workers who previously were found to have low numbers of antibodies.

“People can have antibodies, but it doesn’t mean they are going to be immune,” Dr. Galit Alter, one of the study’s co-authors and a professor of medicine at Harvard Medical School, told the Journal. “The good news is most of the vaccines induce [antibody] levels way higher than these levels,” Dr. Alter added.

Scientists are still researching whether catching COVID-19 provides any form of lasting immunity.

Dr. Alter also told the Journal Elon Musk took a personal interest in the research and had the study’s authors brief himself and SpaceX executives on how vaccines and antibodies work.

SpaceX was able to repurpose medical facilities it had already set up before the pandemic, and recruited interns from nearby hospitals to help draw the volunteers’ blood. Out of 4,300 volunteers 120 who tested positive for COVID-19 had their blood carefully examined to see how many antibodies they’d produced. Out of this 120, 61% reported no symptoms.

Out of that 120-strong sample 92% were male and the median age was 31. The larger sample was 84.3% male with a median age of 32 – although the age range spanned from 18 to 71.

Elon Musk himself said he’d tested positive for coronavirus in November last year, and in the early months of the pandemic the billionaire repeatedly vented his frustration at lockdown measures calling them “fascist.” At one point he defied a shelter-in-place order to open his Tesla factory in Alameda County, California, – after which several employees tested positive for coronavirus.

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