With covid-19 cases once again rising in the U.S.—fueled by the emergence of the more transmissible Delta variant—even vaccinated people are understandably worried. This week, new preliminary research seemed to suggest that those given the Johnson & Johnson vaccine would have significantly less protection against Delta than past strains. But other recent research has been more encouraging, and some scientists aren’t so sure that added measures such as a booster shot are warranted for these people, at least not based on the evidence collected so far.
The study that sparked the latest concerns was released as a preprint paper Tuesday on the website bioRXiv and was conducted by researchers from New York University. The team collected blood samples from people vaccinated with either a two-dose mRNA covid-19 vaccine (Pfizer or Moderna) or the Johnson & Johnson single-dose, adenovirus-based vaccine at various time points (the latest being two to three months after vaccination). Then they introduced pseudo-viruses—engineered viral particles that don’t replicate but can be modified to look like other viruses—to these blood samples. They created different versions of faux coronavirus, made to resemble several of the variants that have now become widespread in the world, including Delta. The goal was to see how often people’s neutralizing antibodies specific to the original coronavirus, generated through vaccination, would respond to the replicas of these variants.
People given an mRNA vaccine seemed to produce moderately fewer neutralizing antibodies in response to the variants than the original coronavirus strain, though their overall levels remained high. In those given the J&J shot, however, “a significant fraction of vaccinated individuals” had much lower levels of neutralizing antibodies. In both their study and quotes to the media, the study authors expressed worry about their findings, arguing that people vaccinated with J&J would benefit from a booster shot.
The New York Times’ primary coverage of the research was careful to list its many limitations, namely that it was a small and preliminary study conducted in the lab and not necessarily reflective of the vaccine’s real-world performance. But even the NYT’s original headline (since changed) wasn’t very nuanced, all but declaring that one shot of the vaccine was ineffective against Delta. Thankfully, and as the NYT alludes to, there is reason to suspect that the situation isn’t so dire for the 12 million or so Americans who have received the J&J shot.
Just last week, another study was published in the New England Journal of Medicine, which similarly looked at the immune responses of those who took the J&J vaccine a month and then eight months later. Unlike the other study, they were also able to look at people’s T-cells specific to the coronavirus, a key cog of the immune system’s response to familiar germs. In this study, which also used pseudo-viruses, they only found a modest drop-off in the level of neutralizing antibodies to Delta and other variants, relative to the original strain. These levels also remained stable and sometimes even increased eight months after—evidence of the immune system’s ability to evolve over time by creating a wider range of antibodies that could be more responsive to future variants of a germ. People’s T-cell responses to the virus similarly remained strong over time. The durability and adaptability found in these vaccinated people’s immune systems, the authors argued, further showed that the J&J vaccine should remain a valuable aid in the fight against covid-19.
It should be noted that the NEJM study involved researchers affiliated with J&J, while the NYU study didn’t. And both studies are based on small sample sizes of volunteers, so neither should be taken as gospel on their own. But given the data so far, it’s premature to say that the J&J shot is ineffective against Delta. And it’s likely not enough to call for a widespread revaccination campaign for these one-shotters, according to Tim Lahey, an infectious diseases physician and medical ethicist.
“Lab findings—such as the level of antibodies elicited by a given vaccine against a given viral variant—are intriguing and worthwhile, but they don’t rise to the level of evidence we need to make confident clinical recommendations. They are hypothesis generating, not practice changing,” he told Gizmodo.
“To make a clinical recommendation, we need evidence that that change will improve outcomes we care about in the lives of real people,” he added. “Does using one vaccine over another, or adding a booster shot to an existing vaccine series, prevent hospitalization and/or save lives, or not? That’s the real question, and without it I think all the confident hypothesizing in the world can’t make it true.”
Some of this real-world data will be available soon enough. In South Africa, where the J&J vaccine is also widely used and Delta has become widespread, researchers are now studying vaccinated health care workers to see how often they still become sick with covid-19. Results from this research, called the Sisonke trial, are expected to come out sometime next month. Earlier this month, however, researchers with the Sisonke trial released a statement in response to growing cases of Delta in the country. They noted that while breakthrough infections were happening among those vaccinated with the J&J shot, so far their data showed that 94% of these cases were mild, while 2% were considered severe. Though the J&J shot has consistently been less effective at preventing any illness from covid-19 than the mRNA vaccines, it’s still been considered about as highly effective at preventing hospitalizations and deaths as the latter.
Of course, people should feel free to do what they think is best for themselves or their families. Some people, including scientists and doctors, have felt cautious enough to recommend a booster shot or to get a booster themselves following their own J&J shot. And there is evidence that mixing-and-matching different types of vaccines may amplify people’s immune response to the coronavirus. Right now, though, we should be a bit more careful about overturning our priors on what we know about the pandemic and the vaccines used to protect us from it, Lahey says.
“We are all so worn out from the epidemic and eager to pin down some sense of certainty. There are also lots of confident and knowledgeable people putting forward a number of well-intentioned theories,” he said. “This is just another time it makes sense to pause, take a deep breath, and insist that our patient care be founded on the same kind of airtight scientific evidence that led to the use of effective vaccines against covid-19 in the first place.”