Pfizer COVID-19 Vaccine is 90% Effective in Early Results: Why We Need More Info

  • Preliminary results from Pfizer’s late-stage vaccine trial suggest the vaccine can prevent COVID-19.
  • This promising development comes as the United States reached another grim milestone of 10 million coronavirus cases, with over 238,000 deaths.
  • The company plans to seek emergency use authorization from the FDA this month.

Drugmaker Pfizer said on Monday that an early analysis of data from its late-stage coronavirus vaccine trial suggests that the vaccine can prevent COVID-19 in people who have not been exposed to the virus before.

This promising development comes as the United States reached another grim milestone of 10 million coronavirus cases, with over 238,000 deaths.

Worldwide, more than 1.2 million people have died of COVID-19.

The Pfizer vaccine has been tested on over 43,000 people, with no serious safety concerns observed, the company said in a news release.

In the phase 3 trial, people were randomly assigned to receive two doses of the vaccine — 28 days apart — or an inactive placebo. Participants did not know which group they were in.

Seven days after the second dose, the vaccine had an efficacy of over 90 percent, the company reported.

Dr. Sunil Sood, chair of pediatrics and an infectious disease specialist at Northwell Health’s Southside Hospital, says the preliminary results are very promising.

“This shows that most people who developed infection were placebo recipients,” he said, “and most of those who got the actual vaccine did not get infected.”

The company said it plans to seek emergency use authorization from the Food and Drug Administration (FDA) by the third week of November.

By then, researchers will have followed participants for an average of 2 months after their second dose, as recommended by the FDA.

The company also said in its release that it expects to produce up to 50 million doses of the vaccine in 2020 and up to 1.3 billion doses in 2021.

Many questions about vaccine remain

Dr. Carlos Malvestutto, an infectious disease expert at The Ohio State University Wexner Medical Center, says the interim results of Pfizer’s trial are very encouraging.

“Obviously, 90 percent protection is the level of protection that we would love to have for all vaccines,” he said.

If the efficacy seen during the interim analysis holds through the remainder of the trial, it will exceed the 50 percent efficacy target set by the FDA for coronavirus vaccines.

Ninety percent efficacy is also similar to the protection provided by other viral vaccines, such as HPV, chicken pox, and measles.

Some researchers, though, told Healthline that not enough data has been released for them to comment on the preliminary results.

Pfizer, which developed the vaccine in collaboration with German biotech company BioNTech, released the interim results in a news release, not a peer-reviewed medical journal.

The company plans to do a final analysis when it reaches 164 confirmed COVID-19 cases.

However, many questions about the vaccine still need to be answered.

David Verhoeven, PhD, a researcher with the Nanovaccine Institute and an assistant professor of veterinary microbiology and preventive medicine at Iowa State University, says the level of protection seen during the interim analysis looks good, but it’s not clear how long it will last.

“We know from natural [coronavirus] infection that immunity may wane in 4 to 6 months,” he said. “[If this happens with the vaccine], you will likely need yearly booster shots.”

Also unclear is whether the vaccine protects against severe disease, which increases the risk of dying from COVID-19.

“If researchers can show that people who are vaccinated and still get COVID-19 have milder disease, that would be a huge winner,” said Malvestutto.

For the interim analysis, researchers only looked at whether the vaccine prevented symptomatic coronavirus infection, which includes mild and moderate cases.

Given the recent surge in coronavirus cases in the United States, Malvestutto says researchers will likely see enough severe cases to know if the vaccine helps this group of people.

He says that we will also need longer-term data about the safety of the vaccine, even though Pfizer will meet the FDA’s minimum recommendations for assessing safety.

Researchers plan on following participants for 2 years after their second dose. The Centers for Disease Control and Prevention also routinely monitors the safety of vaccines approved by the FDA.

Pfizer’s vaccine was not developed as part of Operation Warp Speed, the U.S. government’s coronavirus vaccine effort.

However, the Trump administration did agree in July to buy at least 100 million doses. Under this arrangement, Americans would receive the vaccine free of charge.

Multiple vaccines needed to control pandemic

While Pfizer’s is the first vaccine to show promising results in a phase 3 trial, 10 other vaccines have reached this stage. These include a wide range of vaccine technologies.

Pfizer’s vaccine uses messenger RNA, or mRNA, to elicit an immune response in people who receive the vaccine. Moderna’s vaccine is also based on this technology.

This newer vaccine platform is being tested for use against other infectious diseases such as seasonal flu, Zika virus, and rabies, but none have been approved yet for use in people.

Other technologies being used against the coronavirus include vaccines based on a DNA platform, weakened or inactivated versions of the virus, viral protein subunits, virus-like particles, or delivering a coronavirus protein using another virus.

Some of these technologies are new, while others have been around for years.

“With both old and new technologies being used, our chance of getting several successful vaccines is actually very high,” said Sood.

Given the size of the pandemic, multiple vaccines may be needed.

“We’ll need more than one vaccine that has good protection and is safe and well tolerated,” said Malvestutto, “because that’s the only way we’re going to be able to really get control of this pandemic in a reasonable time.”

However, finding a safe and effective vaccine is just one hurdle that needs to be overcome.

Vaccines would still need to be manufactured and distributed. Pfizer’s and Moderna’s vaccines require ultra-cold storage, which adds another layer of complexity to distribution.

Convincing people to actually get vaccinated is another challenge.

An Axios-Ipsos survey from October found that only two-thirds of Americans said they would get a coronavirus vaccine if it had been approved by the FDA.

“You can have the most amazing vaccine,” said Malvestutto, “but if people don’t take it, then that’s obviously not going to help.”

One STAT-Harris poll, though, suggests that people may be more willing to be vaccinated if the vaccine has a higher efficacy.

But Sood says more work needs to done to convince people to get vaccinated, especially among hard-hit groups such as the Black and Latino communities.

“A lot of community action at the local grassroots level will be needed to explain the safety and efficacy of the vaccine, as well as the importance of getting this vaccine,” he said.

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