Life post-pandemic is around the corner, but the spread of the highly transmissible Delta variant has thrown a wrench to the nation’s progress. The two mRNA vaccines by Pfizer and Moderna are effective at combating the variant, but the science is less clear on Johnson & Johnson’s one-shot wonder. Experts are now considering following up the single jab with a second dose of mRNA to produce a more robust, longer-lasting immune response against the troublesome variant.
Researchers have ascertained that though the Delta variant, first identified in India, doesn’t appear to be as deadly as other strains, it is the most contagious yet. It’s as much as 60 percent more transmissible than the Alpha variant discovered in the U.K., which itself was more contagious than the original strain of the virus. “Wherever it’s appeared, it spreads very rapidly,” John Moore, a vaccine expert at Weill Cornell Medicine, told Intelligencer. “Delta is taking over.”
In the United States, the variant now accounts for about 20 percent of new infections — a rate that has doubled in recent weeks. During a news conference last Tuesday, White House chief medical adviser Dr. Anthony Fauci said the strain, also known as B.1.617, is the “greatest threat” to the nation’s attempt to tame the pandemic.
Part of what makes Delta concerning is that it’s a fitter version of the original strain, making it more contagious and able to partly evade preexisting immunity. “It’s known to escape the antibody component of the immune response, which is the important part of your protection,” Michael Lin, a Stanford University biochemist, told Intelligencer. A study from Public Health England showed that Pfizer and Moderna, both mRNA vaccines, are doing well at protecting against the Delta variant, with roughly 88 percent effectiveness after the second dose.
But early research indicates that the single-shot, viral-vector Johnson & Johnson vaccine could offer less protection than the two-shot mRNA vaccines. Experts don’t yet have the published real-world data that would tease out just how effective the single-shot vaccine is versus the novel Delta variant, but “it’s probably a safe assumption that the Johnson & Johnson vaccine will lose a little bit of efficacy,” Lin added. “We wish we had exact data, but we can interpolate from what we’ve seen of how the shot responds with the Beta variant — it is very likely that the J&J vaccine will hold up pretty well but take a small hit in efficacy.”
Johnson & Johnson announced late Thursday preliminary data that demonstrates their generated a “strong neutralizing antibody response” to the Delta variant, with 85 percent effectiveness. “Current data for the eight months studied so far show that the single-shot Johnson & Johnson COVID-19 vaccine generates a strong neutralizing antibody response that does not wane; rather, we observe an improvement over time,” Mathai Mammen, global head at Johnson & Johnson, said in a statement.
The nation’s vulnerability to the Delta variant has prompted health experts to look into ways to build immunity. Johnson & Johnson is researching whether a two-dose regimen of their shot is more efficacious. An ongoing trial in the U.S. is looking into adding a single shot of Moderna RNA booster to the vaccine regiment of people who have already been immunized; the trial includes people that have already had the Pfizer, Moderna, or the Johnson & Johnson shot.
A booster strategy already under way overseas is to add the more-effective mRNA shot to the less-effective viral-vector shot. Many people in the U.K. who were vaccinated first with the AstraZeneca vaccine later got a second dose of an mRNA vaccine — mostly because of concerns over a rare vaccine-induced blood clot. An ongoing U.K. clinical trial is looking into different mix-and-match shots, including the AstraZeneca vaccine followed by an mRNA vaccine. Even German chancellor Angela Merkel received a Moderna shot after getting the first dose of AstraZeneca vaccine. In Canada, meanwhile, officials already recommend doing a first dose of AstraZeneca and a second dose with an mRNA vaccine, meaning Pfizer or Moderna. “Canada is taking the lead in terms of applying the most recent scientific understanding to how they administer vaccines,” Lin said.
To be clear, these scenarios outside of the U.S. involved the AstraZeneca shot, not Johnson & Johnson. But, according to Lin, given that the Johnson & Johnson one-shot jab works by a mechanism very similar to the AstraZeneca vaccine, since they’re both viral vectors, “a booster shot of mRNA would be very effective in increasing protection against all variants.”
“It’s hard to predict these things without data,” Soumya Swaminathan, the World Health Organization’s chief scientist, told Intelligencer in an email regarding booster shots for vector-vaccine recipients. “ She added that “it makes sense” that an additional dose of the vaccine would build up antibody levels and that “probably a booster will be beneficial,” but stressed the need to wait for more evidence.
A trio of studies released Monday bolstered evidence that vaccines are key for a return to normalcy and that a mix-and-match approach to vaccines shows promise, the New York Times reports. One (non-peer-reviewed) study, published in the Lancet, found that a mixed dosing schedule of the mRNA Pfizer and viral-vector AstraZeneca shots is safe and generates a strong immune response that can fend off the disease. Another study, published in the journal Nature, found that those who received the Pfizer and Moderna RNA vaccines may have strong, long-lasting immunity for years to come. Meanwhile, in a third study, researchers reported that a third dose of the AstraZeneca vaccine given more than six months after the second led to a substantial rise in antibodies.
Fauci told NPR earlier this month that the U.S. federal government is “preparing to boost people, but we don’t know at exactly what point we will have to do that. But we’re doing tests right now, clinical trials to determine various options for boosting people.”
In Lin’s view, many who accepted the one-shot Johnson & Johnson vaccine did so because they were told not to be picky and to take what’s available. “I think the public-health system owes these people a pathway to the same level of vaccination as the majority of people who received the mRNA vaccine,” he said.
For now, though, the CDC allows the mixing of the mRNA shots only in “exceptional situations.” Moore stressed we’re in a watch, wait, and planning phase regarding booster shots; the Delta variant is of biggest concern to those people who have not gotten any COVID-19 shot yet, be it the Johnson & Johnson shot or any other of the current crop of vaccines. “They’re going to get a rude awakening if Delta hits them,” Moore said. “You can run, but you can’t hide. Eventually the highly transmissible variant will find you.”
