The mRNA COVID-19 vaccine companies in the U.S. are already projected to rake in billions from the initial round of doses globally, with billions more projected for a booster market. But some analysts and experts view the need for boosters with caution.

"I don't think it's an annual market. It shouldn’t be," Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia, told Yahoo Finance.

Geoff Meacham, Bank of America Securities research analyst, and his colleagues said in a recent note that there are several reasons to believe an annual booster market is unlikely.

"There remains a lack of evidence that mutated strains cause more severe disease or significantly avoid vaccine protection against severe disease. There is also an increasing percentage of the population with some level of acquired immunity, either due to primary vaccination or infection. Additionally, a third dose in some populations may provide even more durable protection, further reducing the benefit of additional doses," according to the note.

Meanwhile, Omar Chane, a principal at PwC, said the need for boosters depends on the duration of immunity provided by current vaccines. And even then, Chane said, "If a booster is needed, it is still an open question on how often they will be required (e.g., every year, every two years, etc.), which would impact the market."

"For the next few years, it’s likely that various public health authorities will choose to institute some boosting policies purely from a risk mitigation perspective," he added.

It's why companies like Pfizer (PFE) and BioNTech (BNTX) are projected to split a $33.5 billion windfall for 2021, and something in the ballpark of $20 billion if a thriving booster market appears, which could also be true for Moderna (MRNA).

There is also debate about whether a new round of doses are true boosters or simply an additional shot in what will end up being a primary course of three doses for lasting protection.

If the latter is true, would it throw off booster market projections?

Probably not, according to a Wake Forest University health economist Tina Marsh Dalton.

The companies can still count on "the revenue of everyone that's aging into eligibility, so they are still going to have that constant baseline," she said.

Especially if the virus is around for awhile, and the authorization for younger kids comes through.

As Arnaud Bernaert, former Head of Global Health and Healthcare at the World Economic Forum, said, "I think this will not be the last booster. I think we are in for the long run."

Angry scientists

Meanwhile, some scientists are upset by the White House's decision to greenlight an additional dose for all adults in the U.S. in September.

The announcement by President Joe Biden and the White House COVID-19 Response Team pre-empted the regulatory process, which includes advisory panel meetings of the U.S. Centers for Disease Control and Prevention (CDC) and U.S. Food and Drug administration (FDA).

"We have seen, to date, no evidence" to suggest a need for additional protection, and that is something the CDC should have at least had some data on before the White House and Biden announced the need for boosters, Offit said.

The debate about whether boosters are needed basically considers the following: global needs, duration of protection, type of protection, circulating variants.

If the virus continues to circulate globally, with rich countries boosting and poorer countries unable to control the spread and eventually giving rise to more variants, it will be the equivalent of trying to put out a burning house with a fire extinguisher, Offit said.

"You can put out a small fire in the kitchen, but in terms of keeping the house from burning down, all you need is memory," he said, since a vaccinated person's B-cells have the ability to recall how to fight off the disease.

Booster or third dose?

Some experts believe the new dose falls under the definition of additional dose, as the Delta variant's prevalence as the dominant strain means the need to protect against a new virus altogether — and three mRNA shots would count as the primary course. Others believe this is the start of an annual or regular booster shot.

The nation's top public health agency has explained the difference between booster and additional doses. The latter is simply adding on to provide long-lasting protection. Boosters are given after initial protection is achieved.

Meacham said the key issue at the heart of the debate is a lack of understanding of basic immunology.

"It's totally normal for antibody titers to go down after 6 months, give or take, when you get a vaccine. That's the way the body works," he said.

Offit echoed a similar sentiment.

“Protection against severe illness should remain, I should think for a few years. Because all you need is immunological memory," he said.

Which is why Meacham added, "I think the main issue that you have to reconcile is will people accept living with COVID. As of now the answer is no."

The answer hinges on whether evidence emerges that memory of protection is enough, versus the presence of antibodies in a person.

"I would be surprised if you needed a yearly booster," Offit said. "The only virus that is done for is the flu."

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