The Food and Drug Administration is expected to issue an emergency use license (EUA) to Johnson & Johnson’s covid-19 vaccine soon, possibly as early as this weekend. That decision would make it the third vaccine to become available to Americans. So now is a good time to go through the similarities and differences between J & J’s vaccine and the two already out of Moderna and Pfizer / BioNTech.
The main similarity between all three is their high effectiveness in preventing life-threatening diseases from covid-19. In an FDA analysis of clinical trial data from approximately 40,000 volunteers released On Wednesday, J & J’s vaccine was found to be 77% effective in preventing serious to critical illness 14 days after vaccination and 85% in preventing serious to critical illness 28 days later. Overall, it was thought to be 66% effective in preventing moderate to severe illness for 14 days or more.
The top line numbers are not as impressive as what we saw in clinical trials with the mRNA vaccines developed by Moderna and Pfizer / BioNTech, both of which are more than 90% effective at preventing symptoms. But the most critical goal of any vaccine should be to keep people alive and free from serious complications from the targeted disease – a goal that J & J’s version seems to be achieving very well. In the clinical studies there were no covidrelated hospitalizations or deaths observed in vaccinated humans after 28 days. It is likely that none of these vaccines will be 100% effective in prevention hospitalizations or deaths, but all will significantly reduce the chance of it happening.
The J&J vaccine has its own clear benefits. This is because it is only one shot, unlike the two-dose, one-month schedule recommended for both mRNA vaccines. It is currently being investigated whether a second injection, taken two months later, can increase its effectiveness. But for now, it’s the one-shot version that people will be able to access first, assuming it’s been authorized by the FDA. It is also more stable and durable at higher temperatures, meaning it can be kept longer in a typical refrigerator and without the immediate worries of spoiling once it is taken out. (That said, Moderna’s and even Pfizer’s vaccine doesn’t seem to require ultra-cold storage as originally thought.)
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If you are concerned about the novelty of the mRNA technology behind the other vaccines (which for the sake of clarity, actually three decades old), the J&J vaccine can make you feel more comfortable because of its familiarity. It works through one castrated adenovirus (meaning it can’t make more of itself like normal) to carry the DNA for the coronavirus spike protein, the key the virus uses to invade cells. The fake virus invades a cell and prompts the body to mount an immune response specific to the spike protein – one that should train it against the real thing.
The use of viral vectors as a delivery system in medicine predates the mRNA method and has a longer track record of safety. Although, like the mRNA vaccines, this would be the first adenovirus-based vaccine to be widely used. Adenovirus vaccines have their possible limitations, such as pre-existing immunity to the virus used which could weaken the effectiveness of the vaccine. In the case of the J&J vaccine, it uses a type of adenovirus that infects humans less frequently, which is intended to get around those limitations. And because it has been tested in different parts of the world with similar success, that should allay concerns that its effectiveness will vary greatly from country to country.
The J&J vaccine can also win somewhat when it comes to potential side effects. The most common adverse reactions related to the vaccine were injection site pain (48.6%), headache (38.9%), fatigue (38.2%) and muscle pain (33.2%). In contrast, more than 84% of people who received the Pfizer / BioNTech vaccine experienced pain after the first or second injection, and 60% experienced fatigue. Potentially serious adverse events were rare for the J&J vaccine, and there was no difference in frequency between people receiving the vaccine or placebo, after accounting for possible covid-19 symptoms (0.4% in each group), which should further indicate its safety.
As with other vaccines, people under the age of 60 were more likely to experience symptoms at all, which is likely due to a stronger immune response beforehand. There was a possible but still rare risk of an allergic reaction to the vaccine, but only five patients in the study who received the vaccine had a reaction shortly after the injection, and none of them had a serious reaction known as anaphylaxis. (One patient in the placebo group had a response.)
In its review, the FDA stated that more data would need to be collected before it is clear whether an allergic reaction is a real risk from the vaccine. But it further endorsed the vaccine as safe and effective, stating that their analysis “supported a favorable safety profile without identifying specific safety concerns that would preclude the issuing of an EUA”.
Another consideration is that J & J’s vaccine has been tested in the US, South America and South Africa, at a time when important new variants of the coronavirus are emerging. The data suggests that the vaccine should still provide good, if somewhat reduced, protection against the variant first found in South Africa, probably the most troubling variant of all. And it can also provide some protection against asymptomatic infections, which is a good sign that it will reduce transmission.
On Thursday, the FDA’s Advisory Committee on Vaccines and Related Biologicals will meet to discuss the study data and make their recommendation whether to be licensed for emergency use or not. And if things go as expected, the FDA will approve it shortly after. Once authorized, J&J said they are ready to send nearly 4 million doses immediately. It is said that there will be 20 million doses available by the end of March – a timeline similar to Moderna / Pfizer’s early planned distribution. By then all three companies have promised to make a total of 240 million additional doses available to the public. Currently, there are an average of 1.4 million Americans per day vaccinated
In short, the road to mass vaccination is likely to become less bumpy over time, especially if you have other candidates as expected, have your picture taken later this year. And you shouldn’t worry too much about what specific vaccine to get when you finally qualify, as they will all protect you from the worst that covid-19 can do (although J & J’s vaccine may for some most convenient). More importantly, they will all help end this pandemic as soon as possible.