What Medical Experts Think About Pfizer's New COVID-19 Vaccine

Infectious disease pros share what makes them hopeful, what has them concerned and other takeaways from the coronavirus vaccine news.

Pfizer and partner BioNTech announced Monday that their coronavirus vaccine, a two-dose shot designed with a never-before-approved vaccine technology, is 90% effective.

The news pleasantly surprised the medical community, as many doctors were expecting the first-generation vaccines to only work in 50% to 60% of people.

Health experts agree these preliminary results are promising and exciting, but we still don’t have the full picture. We need much more data to understand which participants got sick and how severe their illness was. Researchers will also need to track the study participants in the months ahead to determine how the vaccine holds up over time.

“It is a win for science, but the battle is not over,” Daniel Fagbuyi, an emergency physician who served as a biodefense expert in the Obama administration, told HuffPost.

Here’s what experts think about the vaccine and the takeaways they want you to know.

The vaccine could be more effective than experts imagined.

According to the Pfizer team, those who got the vaccine were 90% less likely to contract the infection. This is much higher than what infectious disease experts predicted.

“These are very promising results, they’re greater than expectations — we thought this was likely to be around 50% to 60% efficacious in preventing infection, so everybody is surprised that these results are so good,” said Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security and an infectious disease expert.

This level of efficacy is in line with our best childhood vaccinations, like the measles and chicken pox vaccine. “That’s a big thing, that’s a big deal,” Fagbuyi said.

We’re using a brand-new vaccine technology.

The Pfizer vaccine was designed with a brand-new type of vaccine technology that uses messenger RNA (mRNA), which essentially teaches the body how to recognize and attack the coronavirus.

According to Adalja, we’ve never had a mRNA vaccine approved for any other condition, so this is a big first for the country.

Though the short-term safety data on this mRNA vaccine is robust and reassuring, researchers will need to continue following the study participants to see if anyone experiences adverse effects six months or a year after being vaccinated.

“This is great,” said Matthew Heinz, a hospitalist in Tucson, Arizona, who helped coordinate the country’s Ebola response under the Obama administration. “But we may not know what questions to even ask, just because this [technology] is very new.”

“These are very promising results, they’re greater than expectations.”

- Dr. Amesh Adalja, Johns Hopkins University

We don’t know how long the shot will last.

A huge unknown is how long the protection conferred from the vaccine will last.

“I think it’ll take some time to know whether or not we need boosters a year later, two years later — I think it’s too early to say,” Adalja said.

Heinz said people typically don’t have a particularly long-lasting immune response against most coronaviruses that cause the common cold, and it’s unclear how long people’s immune response to COVID-19 will last.

And, though some vaccines provide lifelong protection, the immunity conferred from others ― like the Bordetella pertussis vaccine ― wane as we age.

“There are just some [vaccines] that work just fine and then kind of stop working as well, through no action of ours,” Heinz said.

Mutations don’t seem to be a threat (yet).

While influenza strains mish and mash frequently, SARS-CoV-2 (the virus that causes COVID-19) is relatively stable. Yes, the coronavirus has mutated, but not in a major way.

“I do think the mutations that exist right now with this virus wouldn’t pose a problem for this vaccine, but it’ll be important to track,” Adalja said.

Experts agree that we’ll have to keep an eye on how the coronavirus mutates over time. If it doesn’t shift much, the vaccine could last a long time, but if it mutates dramatically there’s a chance Pfizer’s vaccine could become less effective, Heinz said.

The side effects are minor so far.

The most common side effects reported in the vaccine trial were aches and fevers, which Heinz said is on par with other safe vaccines routinely administered.

The influenza vaccine, for example, is known to give some people low-grade fevers, body aches or swelling where they were injected. The same goes with shots for hepatitis, polio and measles.

“A lot of vaccines can do that, frankly. If that’s the extent of it, that’s great,” Heinz said. These minor reactions happen ― you just dont want to see any serious adverse effects.

“It’ll probably be a good 12 months more or so before we can say that the general public is going to be able to relatively easily come across one of the [vaccines].”

- Dr. Matthew Heinz

Supplies of the vaccine will be limited.

We know the initial supply of a COVID-19 vaccine is going to be limited. There won’t be enough doses to go around, especially because the Pfizer vaccine requires two doses.

“They only have like 50 million doses available, for this year anyway … which basically means they can only vaccinate 20 to 25 million people in the States,” Fagbuyi said.

Pfizer hopes to have over a billion doses available sometime next year. In a population of approximately 330 million people, most Americans are going to have to wait to get vaccinated.

“It’ll probably be a good 12 months more or so before we can say that the general public is going to be able to relatively easily come across one of the [vaccines],” Heinz said.

It needs to be stored at frigid temperatures.

Experts also underscored one major logistical challenge: The Pfizer vaccine needs to be stored at very cold temperatures (we’re talking negative 94 degrees Fahrenheit).

Pfizer previously announced it plans on packing and shipping the vaccines in cases filled with dry ice. Whoever will be administering the vaccine — likely retail pharmacies or hospitals — will need to figure out where and how they’re going to properly store the vaccines.

Most facilities don’t have these tools on hand, so will need to either purchase a lot of dry ice (of which there could be shortages) or invest in on-site cooling units.

“The logistical nightmare is still there. It’s a long haul, it’s still a marathon,” Fagbuyi said.

“Does this vaccine protect against severe disease? That’s the million-dollar question.”

- Dr. Daniel Fagbuyi

We still need more data on the vaccine, like how it affects the severity of COVID-19 and how it impacts different populations.

Even through these preliminary results are promising, researchers are still waiting on a ton of data. Remember, the trials are not yet over and scientists have yet to see how the vaccine holds up in the months and years ahead.

Fagbuyi is most interested in learning about the people involved in the clinical trials who contracted the infection. Because a significant portion of COVID-19 cases are asymptomatic, it’s crucial to ensure the vaccine not only prevents infection but also reduces the severity of the illness and complications in at-risk people who do get sick.

“Does this vaccine protect against severe disease? That’s the million-dollar question,” Fagbuyi said.

It’s also not clear what the demographic breakdown is with Pfizer’s trials. According to Pfizer, 30% of U.S. participants were from racially and ethnically diverse backgrounds, but health experts would like to see specifically how well the vaccine worked in different types of people. Keep in mind, too, that the vaccine has not yet been tested on pregnant women or children either.

The clinical trials must reflect the diversity of the population. If they don’t, some of the findings may not be generalizable. You need young people, older adults, men, women and people of all races.

“Its important to have as much information as possible. You really want to get a representative population,” Heinz said.

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.