With two Covid-19 vaccines available in the United States—and another three major vaccine candidates potentially nearing FDA review—Americans may soon be tempted to pick and choose which vaccine they get. But that mindset might be misguided, according to public health experts.  

The U.S. Covid-19 vaccination scenario planning guide

More vaccines, more choices?

FDA has already issued emergency use authorizations (EUAs) for two Covid-19 vaccines: one produced by Moderna, a two-dose mRNA vaccine that in a clinical trial had shown a 94% efficacy rate against symptomatic infections, and another two-dose, mRNA vaccine by Pfizer and BioNTech, which in its own trial showed a 95% efficacy rate against symptomatic infections.

However, at least three more vaccine candidates are emerging as major players, The Atlantic reports, although—at first glance—they appear to have lower efficacy rates.

Those candidates include AstraZeneca's vaccine, which has already been approved in Britain and has reported an efficacy rate of 70%; Novavax's candidate, which has reported 89% efficacy in Britain but 49% efficacy in South Africa; and Johnson & Johnson's (J&J) candidate, which has reported an overall efficacy rate of 66% against moderate and severe infection, with an 85% efficacy rate against severe Covid-19.  

According to STAT News, at least one of those manufacturers, J&J, is on the cusp of seeking an EUA from FDA—and experts say if an EUA is granted, the vaccine could be a gamechanger for the country's vaccine rollout.

That's in part because J&J's candidate is far easier to store and distribute than the mRNA vaccines, The Atlantic reports. Specifically, J&J's candidate, like Novavax's and AstraZeneca's, can be stored at regular refrigerator temperatures, as opposed to the mRNA vaccines, which require special freezers to maintain subzero storage temperatures. In addition, J&J's vaccine candidate will be reviewed as a single-shot dose, making it far easier to distribute than Pfzier-BioNTech or Moderna's, both of which require two doses spaced at least three or four weeks apart.

But while experts praise the increasing variety of vaccines, and say those options can help facilitate the vaccine rollout, they have also voiced concern that the expanding array of options—and differing reports on efficacy rates, side effects, and more—could make people "want to pick their vaccine as if it were a piece of produce they could squeeze to find the choicest option," STAT News reports.

Which vaccine should you get?

Experts have unanimously encouraged people to get whichever vaccine is most readily available. "In the event that you have the choice to get vaccinated, I'd encourage you to take the vaccine that you're given," John Brooks, CMO of CDC's Covid-19 response, stated.  

Even so, Anthony Fauci, lead medical advisor to President Biden on the novel coronavirus pandemic, acknowledged the allure of Moderna and Pfizer-BioNTech vaccines. "If you woke up and you say, 'Well, go to the door on the left and you get 94 or 95 percent, go to the door on the right and you get 72 percent,' which door do you want to go to?" he asked.

But as Fauci and other experts explained, that's the wrong way to look at it: The efficacy rates available are not directly comparable, given that the drug manufacturers ran their studies in different countries, with differing protocols, and—perhaps most importantly—against a virus that has evolved over time.

Specifically, the Moderna and Pfizer-BioNTech vaccines appear to have been tested primarily against the original strain of the novel coronavirus, early in the pandemic, whereas J&J and Novavax's vaccine candidates were tested later, after several variants had emerged. These variants include B.1.351 in South Africa, which appears to make the virus more transmissible and more vaccine-resistant. 

"You have to recognize that Pfizer and Moderna had an advantage," William Schaffner, an infectious disease expert at Vanderbilt University, explained. "They did their clinical trials before the variant[s] … became very apparent. Johnson & Johnson was testing its vaccine not only against the standard strain, but they had the variants [too]."

Experts also say that, despite the differences in reported efficacy rates, all five vaccines appear to be highly effective—especially considering that FDA originally said it would authorize a vaccine at just 50% efficacy. Citing Novavax's 49% efficacy rate in South Africa, for instance, Kelly Moore, the deputy director of the Immunization Action Coalition, said, "Even that 50% range, given the severity of illness and death toll, would have been a game changer."

Further, all five of the vaccines appear to be very effective at preventing severe illness and fatalities. As Fauci put it, it's more critical to prevent severe cases of Covid-19 than to fend off "some aches and a sore throat"—and all the candidates seem well poised to do that. In fact, of the 75,000 patients who received the five major vaccine candidates in clinical trials—including in studies in the United Kingdom, Brazil, and South Africa—not a single one has died from Covid-19. And none of the candidates in J&J's latest clinical trials who received the vaccine became sick enough to require hospitalization.

"If you can prevent severe disease in a high percentage of individuals," Fauci said, "that will alleviate so much of the stress in human suffering and death in this epidemic that we're seeing, particularly now."

Separately, Francis Collins, director of the National Institutes of Health, pointed out that the vaccines' ability to stave off severe disease is comparable to that of flu shots, which may not always prevent infection but often make any potential infection less severe. "The same thing seems to be applying here, in a circumstance where this variant is clearly making it a little tougher to get the most vigorous response that you would want to have," he said. "But still, for severe disease, it's looking really good."

So, overall, if it came down to getting the J&J vaccine tomorrow versus receiving the Moderna or Pfizer-BioNTech vaccines a few weeks down the road, public health experts recommend getting "the one tomorrow," Schaffner said. "The virus is bad. You're risking three more weeks of exposure as opposed to getting protection tomorrow."

What does a (potentially) wide variety of vaccines mean for rollout?

According to experts, this potentially wider array of vaccines could further complicate an already difficult rollout—even as it facilitates overall access.

For instance, the J&J vaccine, if granted an EUA, would be far easier than the currently available vaccines in the United States to transport and administer, given its easier storage requirements and one-shot delivery—a benefit for rural populations and other "hard-to-reach" areas, according to Mitchel Rothholz, chief of staff at the American Pharmacists Association. In turn, it would be easier for health care providers to deliver within communities, rather than requiring people to come to clinics, hospitals, or other health care facilities.

On the flip side, if different vaccines show different efficacy levels, targeting them to different populations could create ethical concerns, STAT News reports. For example, if states were to distribute J&J's vaccine—if granted an EUA—primarily to rural areas, "there may be concerns that's inequitable," Marcus Plescia, CMO of the Association of State and Territorial Health Officials, said. "People in rural areas might feel like they're getting short shrift."

Julie Swann, the head of the department of industrial and systems engineering at North Carolina State University, recommended that providers start polling their communities on their vaccine preferences, arguing, "It would be a real mistake to distribute J&J solely based on infrastructure."

However, Swann and other experts noted that there may be other reasons to target specific vaccines to certain groups of people. For instance, as Swann hypothesized, perhaps officials would reserve the mRNA vaccines for high-risk people, while the J&J vaccine is distributed for more general populations.

Ultimately, however, speed is the most critical component of the rollout. "The sooner we can get people immunized, the better chance we have that this will not keep happening with more and more variants emerging because there's such a large population of viruses," Collins said (Joseph/Goldhill, STAT News, 1/29; Grady, New York Times, 1/31; Zhang, The Atlantic, 1/29).