• Lea Kapur

Is There a “Best” Vaccine in the U.S.? A Deep Dive Into The Three Vaccines Approved in the U.S.

Updated: Sep 28

With three vaccines authorized by the federal government and distribution increasing, the end of the COVID-19 pandemic appears in sight. But, as you make your vaccination appointment, you may ask yourself, is there a best vaccine among the three? Should I hold out for the best one or get vaccinated now?

The three vaccines currently available are Pfizer-BioNtech, Moderna, and Johnson & Johnson/Janssen, according to the Center for Disease Control and Prevention (CDC). Both the Pfizer-BioNtech and Moderna vaccine are mRNA vaccines; if you have an allergy to mRNA vaccine types, Johnson & Johnson/Janssen is a suitable alternative, as it is a viral vector vaccine. The Pfizer-BioNTech vaccine is a two-shot vaccine. It is required for the shots to be given 21 days apart and in the muscle of the upper arm. The vaccine is safe for people ages 16 and older, according to the CDC. The Moderna vaccine is very similar to the Pfizer-BioNtech vaccine. It also requires two doses, but a 28-day interlude. It is given in the same part of the arm and is safe for people ages 18 and older, according to the CDC. The Johnson & Johnson vaccine differs from the other two vaccinations as only one shot is required. It is still given in the same part of the arm and is safe for people ages 18 and older, according to the CDC.


The vaccines are also similar in terms of symptoms of reported side effects and their onset. People have reported side effects at the site of vaccination and in the rest of the body. The side effects for the arm are pain, redness and swelling. For the body as a whole, tiredness, headaches, muscle pain, chills, fever and nausea have been reported. The side effects usually begin within a day or two after receiving the vaccines, but usually go away within the next couple of days and are moderate in nature. These side effects are completely benign and indicate that the body's immune system is producing a successful response to the virus in gaining immunity.


Another similarity between the vaccines is the possibility of protection against asymptomatic infection. Early evidence suggests that the Johnson & Johnson/Janssen vaccine may be able to “provide protection against asymptomatic infection, which is when a person is infected by the virus that causes COVID-19 but does not get sick.” Furthermore, a 2021 study conducted by researchers from Cambridge University indicated that the Pfizer-BioNTech vaccine is 94% effective against asymptomatic infection.


A major point of confusion is the difference between vaccine efficacy, vaccine effectiveness, and the different data points between the three vaccinations. Furthermore, there has been a question of whether the differences in data points are statistically significant enough to determine that one vaccine is better than another. Shelly McNeil, a doctor from the Canadian Center for Vaccinology, defines vaccine efficacy as the “[percent] reduction in incidence in a vaccinated group compared to an unvaccinated group under optimal conditions.” The keywords are “under optimal conditions.” The three vaccines were not tested under these conditions which makes efficacy predictions difficult. It is critical to note that all vaccine reduced serious or severe infection symptoms by 100%.


Carl Zimmer, a science writer from The New York Times, explains how the Johnson & Johnson/Janssen trials started months after both of the other two vaccines. “So by the time that Johnson & Johnson had a lot of recruits getting vaccinated, we were in the middle of an intense surge of Covid [...] [and that] vaccine developers have found [...] that if you run a trial when rates are really high, you might end up with an efficacy estimate that ends up being low. And that’s just because your volunteers are getting exposed to the virus more. [...] If rates are low, people just might not have the opportunity to get sick in the first place, and you don’t really put your vaccine to as much of a test.” Therefore, while the Pfizer-BioNTech vaccine has a 95% efficacy rate and the Moderna vaccine has an efficacy of 94.5%, these vaccines were tested under different conditions when compared to the Johnson & Johnson/Janssen vaccine. So, while the Johnson & Johnson/Janssen vaccine only has a 72% efficacy, this is likely a low efficacy estimate when compared to the other vaccine efficacy rate. This is due to the heightened COVID-19 surge during the trial date.


McNeil also defined vaccine effectiveness as the “ability of [a] vaccine to prevent outcomes of interest in the ‘real world.’” Once again, the different test conditions make it hard to directly compare the effectiveness of each vaccine. “Based on evidence from clinical trials, the Pfizer-BioNTech vaccine is 95% effective.” The Moderna vaccine has a similar effectiveness rate at 94.1%. Finally, Johnson & Johnson/Janssen has a lower effectiveness rate at 66.3%, but it is the difference in test conditions likely highly due to different test conditions.

Andrew Thomas, a chief clinical officer at The Ohio State University Wexner Medical Center, says it best — “the vaccine that’s best for you is likely the vaccine that’s available to you.” Do not wait around for a vaccine that “appears” better, the sooner you get vaccinated, the sooner you gain heightened protection from COVID-19 and life can slowly start to return to normal.