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The world has been waiting for good news on Covid-19 vaccines. Monday it got a bunch of it.

A preliminary analysis of the race frontrunner, Pfizer-BioNTech’s mRNA vaccine, suggested it was 90% effective in preventing symptomatic Covid disease. While these are early findings — the trial is still ongoing — they suggest the vaccine could be very protective.


There’s another important caveat. We don’t yet have details about whether the vaccine blocked mainly mild cases, or if there is evidence that it seemed to prevent some severe infections, too.

Still, the early results are encouraging for the Pfizer-BioNTech partnership. But embedded in the announcement is broader good news for Covid-19 vaccine development. Here are four reasons for encouragement based on the early results, starting with the most important.

We are likely to have multiple successful Covid-19 vaccines.


The Pfizer vaccine targets the spike protein, the knobby protrusion on the SARS-CoV-2 virus that allows the virus to attach to and invade human cells, initiating infection.

In fact, all of the vaccines being developed by major manufacturers working with Operation Warp Speed, the U.S. government effort to fast-track vaccines, target the spike protein.

There have been at least theoretical concerns that this was the vaccine development equivalent of putting all our eggs in one basket. The interim Pfizer data suggests the basket is the right one.

“There was always a discussion: Is the spike protein the right target? Well, now we know it’s the right target,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told STAT on Monday. “So, it’s not only immediate good news, it really is optimistic about what’s going to roll out in the next several months with the other vaccines.”

That forecast applies globally. All the vaccines being developed with the help of the Coalition for Epidemic Preparedness Innovations — which has been funding research and production with the aim of producing vaccine for worldwide distribution — target the spike protein.

“We believe these interim results also increase the probability of success of other Covid-19 candidate vaccines which use a similar approach,” CEPI CEO Richard Hatchett said in a statement.

This is terrific news for mRNA vaccines.

The two frontrunners in the race to develop Covid vaccines are Pfizer and Moderna; both use a new vaccine production technology known as mRNA. (Other manufacturers, including vaccines giant Sanofi, are developing mRNA vaccines, but they are not as far along in the work.)

Research has been underway for years on this innovative approach to make vaccines, but to date no mRNA vaccine has been brought to market.

The platform offers huge promise, both in terms of how quickly a vaccine can be designed and how quickly batches can be made. But there are no givens in vaccine development. Until something is shown to work, you don’t know that it will.

Scientists can now design genetic material called mRNA to help us build immunity to certain viruses, including SARS-CoV-2, the coronavirus that causes Covid-19. Find out how mRNA vaccines work in this video. Hyacinth Empinado/STAT

Pfizer’s early results will likely have sparked celebrations too in the Cambridge, Mass., offices of Moderna.

“It validates the mRNA platform,” Fauci said. “You have every reason to believe, unless something strange happens, that Moderna will likely have similar results.”

That would be extra sweet news for Fauci. The vaccine construct Moderna is developing was created in NIAID’s vaccine research center.

We may be able to expect more from Covid-19 vaccines than we thought. That could help persuade people to be vaccinated.

It’s early and, as Fauci told STAT on Monday, we don’t want to get ahead of ourselves. Plus, it’s important to note that at this point, there’s no way to estimate how long protection from this or any Covid vaccine would last. The duration of protection will only become clear after the vaccines are in use for a while.

But there has been a fear with Covid vaccines that they might not be super protective. Many vaccines targeting pathogens that invade our respiratory tracts — think flu vaccine — don’t generate terrific immune responses.

The relatively low bar the Food and Drug Administration set for Covid vaccines was seen by many as lowering expectations. The FDA told manufacturers in guidance issued in June that it would accept a vaccine that reduces the risk of symptomatic Covid by 50%.

“This vaccine could be more effective than we ever hoped for from the first generation of Covid-19 vaccines,” Jeremy Farrar, director of the Wellcome Trust, said in a statement.

That could be very good news not just for people who get the Pfizer vaccine, if and when it gets cleared for use. It could also boost confidence in Covid vaccines.

As presidential politics have swirled around the development and approval of the Operation Warp Speed vaccines, polls have shown that the public was becoming wary of them.

If the early promise of the Pfizer vaccine holds, that could really help persuade people that getting vaccinated against the SARS-2 virus is worthwhile, Fauci said.

“Vaccine hesitancy diminishes proportionately inversely with the efficacy of a vaccine,” he said. “I think this is going to go a long way to diminishing the vaccine hesitancy that we see.”

Pfizer’s vaccine’s long-term prospects now look better.

Pfizer’s vaccine will almost certainly be the first to be authorized by the FDA. But it’s also going to be the hardest one to use.

The vaccine has to be shipped and stored at ultra-cold temperatures, -94 Fahrenheit (-70 Celsius). That requirement will limit where the vaccine can be used. Moderna’s mRNA vaccine must be stored at -4 F (-20 C), which is not ideal, but not quite as challenging.

Still, a vaccine that might be 90% efficacious becomes more attractive — regardless of distribution challenges.

Moncef Slaoui, co-chair of Operation Warp Speed, told STAT last week that the storage requirements have been a topic of discussion between the U.S. government and Pfizer. The Pfizer vaccine is not being developed as part of Operation Warp Speed, but the U.S. has pre-purchased 100 million doses of it, with an option to buy an additional 500 million more.

“There were tradeoffs in their case between the speed with which vaccine would be available and identifying the right formulation that would be stable,” Slaoui said.

“Both [Pfizer and Moderna] are working on improving the stability, the cold chain requirements to at least 2 C to 8 C degrees,” he said, referring to standard refrigerator temperature in Celsius. “And I am confident they will find solutions.”

Correction: An earlier version of this story misstated the temperature at which Moderna’s mRNA vaccine must be stored.

  • Great way forward through science. I am only concerned about the stability of the vaccine given the half life of mRNA molecules is too short. The logistics like storage at -70 deep freezers means it will be really tough for mass distribution at least in the developing and poorly equipped nations. Companies making -70 C deep freezers would be looking forward to big boom.
    Good luck

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