The Food and Drug Administration is expected to grant an emergency use authorization (USA) to Johnson & Johnson’s covid-19 vaccine soon, possibly as soon as this weekend. That decision would make it the third vaccine of its kind available to Americans. So this is as good a time as any to discuss the similarities and differences between the J&J vaccine and the two that have already come out of Moderna and Pfizer / BioNTech.
The most important similarity between the three is their high effectiveness in preventing fatal diseases from covid-19. In an FDA analysis of clinical trial data from about 40,000 volunteers published On Wednesday, the J&J vaccine was found to be 77% effective in preventing critical illness 14 days after vaccination and 85% effective in preventing critical critical illness 28 days later. Overall, it was considered 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 of mRNA vaccines developed by Moderna and Pfizer / BioNTech, which are more than 90% effective in preventing any symptoms. But the most important goal of any vaccine should be to keep people alive and free from serious complications of the target disease, a goal that J & J’s version seems to accomplish very well. In clinical trials, there was no covidityrelated hospitalizations or deaths observed in vaccinated persons after 28 days. None of these vaccines are likely to be 100% effective in preventing hospitalizations or deaths, but all will greatly reduce the chances of it occurring.
The J&J vaccine has its own clear benefits. That is, it is just one injection, as opposed to the two-dose schedule for a month recommended for any mRNA vaccine. Research is ongoing that tests whether a second injection, taken two months later, could increase its effectiveness. But for now, it’s the only version that people will have access to first, assuming it’s cleared by the FDA. It is also more stable and durable in warmer temperatures, which means it can be stored in a typical refrigerator for longer without the immediate concern of spoiling once it is removed. (That said, Moderna and even Pfizer’s vaccine don’t seem to need ultra-cold storage as originally thought.)
If you are concerned about the novelty of mRNA technology behind the other vaccines (which, to be clear, is actually three decades old), the J&J vaccine may make you more comfortable because of its familiarity. It works using a castrated adenovirus (which means it can’t make more of itself as usual) to carry the DNA of the coronavirus spike protein, the key the virus uses to invade cells. The dummy virus enters a cell and causes the body to generate an immune response specific to the spike protein, one that should train it against the real protein.
The use of viral vectors as a delivery system in medicine is older than the mRNA method and comes with a longer history of safety. Although, like mRNA vaccines, this would be the first adenovirus-based vaccine to have widespread use. Adenovirus vaccines have their potential limitations, such as pre-existing immunity to the virus used that could weaken the effectiveness of the vaccine. In the case of the J&J vaccine, a type of adenovirus is used that infects people less frequently, which is intended to avoid these limitations. And because it has been tested in different parts of the world, with similar success, that should ease concerns that its effectiveness will vary greatly from country to country.
The J&J vaccine may also win slightly when it comes to potential side effects. The most common vaccine-related adverse events were injection site pain (48.6%), headache (38.9%), fatigue (38.2%), and myalgia (33.2%). In contrast, more than 84% of people who received the Pfizer / BioNTech vaccine experienced pain around the injection site 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 who received the vaccine or placebo, after accounting for possible covid-19 symptoms (0.4% in each group ), which should also indicate your safety.
As with other vaccines, people under the age of 60 were more likely to experience any symptoms, which is likely due to a stronger initial immune response. There was a possible, but still rare, risk of an allergic reaction to the vaccine, but only five study patients who received the vaccine had a reaction shortly after the injection, and none experienced a serious reaction known as anaphylaxis. (One patient in the placebo group had a reaction.)
In its review, the FDA stated that more data should be collected before it is clear whether the allergic reaction is a real risk from the vaccine. But otherwise, he endorsed the vaccine as safe and effective, stating that his analysis “supported a favorable safety profile with no specific identified safety concerns that would preclude the issuance of an EUA.”
Another consideration is that the J&J vaccine was tested in the US, South America and South Africa, during a time when important new variants of the coronavirus have begun to appear. The data suggest that the vaccine should provide good, albeit slightly diminished, protection against the variant first found in South Africa, probably the most worrisome variant of all. And it may also offer some protection against asymptomatic infections, which is a great sign that it will reduce transmission.
On Thursday, the FDA’s Vaccines and Related Biologics Advisory Committee will meet to discuss the trial data and provide their recommendation for an emergency use authorization or not. And if things go as expected, the FDA will authorize it soon after. Once authorized, J&J has saying they will be ready to ship almost 4 million doses immediately. By the end of March, it is said to have 20 million doses available, a timeline similar to Moderna / Pfizer’s planned initial distribution. By then, all three companies have promised make 240 million more doses available to the public in total. Currently, 1.4 million Americans on average per day are being vaccinated.
In short, the road to mass vaccination is likely to become less bumpy over time, especially if other candidates enter the picture later this year as expected. And you don’t need to worry too much about which specific vaccine to get when you’re finally eligible, as they will all protect you from the worst COVID-19 can do (although the J&J vaccine might be the most convenient for some). Most importantly, everyone will help end this pandemic as soon as possible.