Is Johnson & Johnson’s Covid-19 vaccine a game changer?

Sam Fazeli, a Bloomberg Opinion contributor who covers the pharmaceutical industry for Bloomberg Intelligence, answered questions about Johnson & Johnson's one-dose Covid-19 vaccine. The pharmaceutical giant released promising early-stage trial data on its ability to fight the disease, expanding on results the company first published in September. The conversation has been edited and condensed.

Johnson & Johnson's vaccine will be another weapon in the fight against Covid-19. What do these findings say about how well it works and how it compares with others?

We won't know the efficacy of the vaccine for another couple of weeks — that's when the first results from late-stage, phase III trials will be reported — but the data from an earlier stage in the trial that was just published in a peer-reviewed article in the New England Journal of Medicine helps us make some predictions. The findings, looking at various aspects of the immune response after one or two doses, look better than the preliminary report from the same trial that we saw in September. After just one dose, the immune reaction looks similar to that seen with two doses of the Pfizer Inc.-BioNTech SE and Moderna Inc. vaccines, though it's important to note that different methods were used to measure antibody levels, so they are not directly comparable. What's also good is that the antibody response continued to remain strong and even improved up to 71 days after the first dose, while the effect in people older than 65 was pretty much the same as that seen in younger adults. Given all this, and the fact that the Pfizer vaccine had close to 90% efficacy in its phase III trial between the first and second dose, I am optimistic that J&J's phase III will also report very strong efficacy.

How does the J&J vaccine work?

J&J's vaccine uses the same type of "viral-vector" technology that's used in the shot developed by AstraZeneca Plc and the University of Oxford as well as Russia's Sputnik V vaccine. In all these cases, other viruses — typically adenoviruses that cause the common cold, either in humans or primates — are engineered to deliver the genetic material for the Sars-Cov-2's key "spike" protein instead. This causes the immune system to raise a response to the spike protein as well as other parts of the adenovirus vector that is used.

What's the timing? If it looks so good early on, can we expect approval soon?

While the immunological data look great, a large phase III trial is needed to figure out the efficacy of the vaccine in preventing disease and, perhaps even more important, its safety profile in a large diverse group of people. One important difference about the J&J trial is that its main goal is to determine how well the vaccine reduces the risk of moderate to severe disease. The other trials looked only at severe disease as a secondary outcome measure. So the J&J phase III trial will directly answer the question of how well severe disease was reduced.

Assuming the phase III data is positive, how will it factor into the vaccine rollout?

Many people should rightly rejoice if the J&J phase III trial reports as strong an efficacy as we expect it to. The shot will greatly help vaccination efforts and could be a game changer. It will be a single-shot vaccine that can be stored and transported at refrigerator temperatures unlike those of Pfizer-BioNTech and Moderna, which require various degrees of freezing. J&J has done global deals for an initial 900 million doses of the vaccine, plus a potential further 400 million doses under option. But J&J has already hit some production snags, according to the New York Times, with production unlikely to reach high volumes until April or May. So even if its profile makes it one of the best vaccines out there, we will still need all the other shots to help us beat this pandemic.    

Is a single shot really enough?

How long the protection lasts will not be known for a long time, but the 71-day antibody response cited above is promising and suggests a single dose is sufficient, at least in the near term. But there is an open question about whether a second dose would be better over the long term. In the data just published, a second dose 57 days after the first certainly boosted the immune response in young adults. So it's possible that a second shot will eventually be needed for longer-lasting protection. 

Is there any sense of how the J&J vaccine works against the variants that emerged in the U.K. and South Africa, which appear to be more transmissible?

The conventional wisdom for all of these vaccines is that even if there is an effect, it will be one of reduced efficacy, not total loss. A slow loss of efficacy would be expected over time anyway, just like our natural immune reaction to the versions of other coronaviruses that cause mild disease. The adenoviral-based vaccines like J&J's and Astra's are easily adaptable to the evolving virus. But a theoretical problem would be that if we do need updated versions, the immune reaction to the adenoviruses that are employed to carry the genetic material may limit their efficacy. We'll have to watch this.