When the curtain finally closes on 2020, it'll go down as one of the wildest and most disruptive years on record. That's because the coronavirus disease 2019 (COVID-19) pandemic has completely upended societal norms and transformed the traditional work environment almost overnight.

However, there is hope that an end to the pandemic is near. That's because the healthcare stocks behind three of the four most-promising coronavirus vaccine candidates reported interim and/or final data from ongoing late-stage studies in November. Suffice it to say, efficacy and safety data from these data releases blew researchers' expectations out of the water.

But it's imperative that prospective consumers and investors understand that no two vaccines are alike. Each of the four most promising, late-stage candidates brings at least one key advantage and one sizable drawback to the table, relative to their peers. Let's take a closer look at where the strengths and weaknesses of these COVID-19 vaccine candidates lies.

A senior woman being administered a vaccine by a physician.

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Pfizer/BioNTech

Perhaps the most well-known vaccine is the Pfizer (NYSE:PFE)/BioNTech (NASDAQ:BNTX) candidate, BNT162b2. I saw well-known because it was recommended by a Food and Drug Administration (FDA) panel for emergency use on Dec. 10. It's also been approved for use in Canada and the United Kingdom. 

The biggest advantage: What's allowed BNT162b2 to stand out in a potentially crowded field of candidates is its efficacy. An update from Pfizer/BioNTech revealed a final vaccine effectiveness (VE) of 95%, which is the highest VE we've seen to date, in terms of COVID-19 prevention. Most researchers were expecting a VE of 50% to 60%, which is more in-line with what we see, on average, from influenza vaccines. A 95% VE could yield true pandemic-halting results.

It's also worth noting that the Pfizer/BioNTech vaccine will get the first crack at commercialization in a handful of markets. However, its first-mover advantage isn't expected to last long.

The biggest drawback: On the other hand, BNT162b2 could be an absolute nightmare to distribute. That's because it needs to be stored at close to minus 100 Fahrenheit during transport, which is well beyond the temperature range of most freezers found in pharmacies and hospitals. While solutions do exist (e.g., dry ice), getting the vaccine to its desired location won't be easy.

Multiple syringes lying atop a messy pile of cash.

Image source: Getty Images.

Moderna

Another high-profile COVID-19 vaccine candidate generating a lot of buzz is Moderna's (NASDAQ:MRNA) mRNA-1273. Moderna reported its interim analysis data just a week after Pfizer lifted the hood on its initial results, stoking hope in the U.S. and worldwide that an end to the pandemic is growing near. Having partnered with Lonza Group, Moderna aims to produce and distribute between 500 million and 1 billion vaccines in 2021.

The biggest advantage: A case could be made that Moderna's 94.1% VE, 100% VE against severe COVID-19 cases, or perhaps its status as the first to begin human clinical trials, are its biggest advantages. However, I'd pinpoint safety as Moderna's differentiating tool. The phase 3 COVE study featured very few grade 3 adverse events, with the most prominent being fatigue (9.7%) after the second dose. With two folks in the U.K. having allergic reactions to the Pfizer/BioNTech vaccine this past week, Moderna's mRNA-1273 may profile as the safest of the bunch. 

The biggest drawback: Comparatively, Moderna's vaccine is also the priciest of the group -- at least of those whose prices we know. The company's CEO, Stephane Bancel, told a German news publication in November that his company intends to charge $25 to $37 per dose, depending on how many doses a country buys. For context, that's between 28% and 90% higher than the Pfizer/BioNTech cost per dose of $19.50. It's not out of the question that this high price point costs Moderna orders.

A lab researcher holding a vial of blood in his left hand while reading from a clipboard in his right hand.

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AstraZeneca/Oxford

Though it hasn't received nearly as much media time as Pfizer/BioNTech and Moderna, the coronavirus vaccine candidate from AstraZeneca (NASDAQ:AZN) and Oxford University, AZD1222, is one of the three to have released interim or final efficacy data.

The biggest advantage: When buying coronavirus vaccines in bulk, price matters. AstraZeneca has pledged to sell its vaccine at cost, which equates to a variable cost of between $3 and $4 per dose. That's a massive dangling carrot that could have countries champing at the bit to purchase AZD1222. Put another way, countries may be able to purchase up to 12 doses of AZD1222 for every dose of mRNA-1273. 

The biggest drawback: The issue for the AstraZeneca/Oxford vaccine is that its efficacy wasn't overwhelming, as with the Pfizer/BioNTech and Moderna vaccines. AstraZeneca's interim analysis showed a combined VE from two dosing arms of 70%. That's still better than what was expected, but not jaw-dropping.

What's particularly odd about the AstraZeneca/Oxford COVID-19 vaccine is the wide variance in VE between its two dosing arms. Patients who received two full doses at least a month apart showed a 62% VE. Meanwhile, patients who were given a half-dose initially and a higher second dose at least a month later had a 90% VE. It's a bit puzzling to researchers, and it's quite possible this uninspiring VE hurts AZD1222's chances of being a hit. 

A half-emptied hourglass on a table next to a calendar.

Image source: Getty Images.

Johnson & Johnson

Lastly, the largest publicly traded healthcare company, Johnson & Johnson (NYSE:JNJ), intends to be a major player with its vaccine candidate JNJ-78436735 (also known as Ad26.COV2.S). Based on interim results from the company's phase 1/2a analysis (updated in October), its investigational vaccine led to detectable antibodies in 99% of participants, with 98% positive for neutralizing antibodies.

The biggest advantage: Aside from Johnson & Johnson's deep pockets, the single biggest advantage is that JNJ-78436735 is a single-dose treatment. If J&J's COVID-19 vaccine produces a VE that's relatively close to Moderna and Pfizer/BioNTech, you can all but guarantee that the U.S. and other countries will be breaking down the proverbial door to get their hands on it. 

The biggest drawback: The clear-cut downside of the Johnson & Johnson candidate is that it'll probably be the last of the four to reach distribution. Even after slashing its phase 3 trial volunteer count from 60,000 to 40,000 this past week -- a move that could be made due to rapidly rising case counts in the U.S. -- J&J isn't expected to unveil an interim analysis readout until January. It could be many months before Johnson & Johnson gets the green light to distribute its vaccine, assuming clinical success. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.