Looks like the one-and-done COVID-19 might end up being two-and-through instead. Despite no evidence yet of a decline in protection from the Johnson & Johnson/Janssen vaccine as seen in the two mRNA vaccines, a new study shows a booster shot amplifies antibody production exponentially. That may have 14 million Americans trekking back to their local pharmacy for a second round — if they can find it:

In the midst of a delta variant surge, a new study finds that giving a booster dose of the Johnson & Johnson shot six months after primary vaccination results in a nine-fold increase of a crucial antibody response, according to a company press release.

Meanwhile, a prior study found that people vaccinated with the Johnson & Johnson vaccine still had a durable immune response at least eight months later, even without a booster.

Collectively, the findings could help inform the U.S. government’s recommendations about booster shots for the 14 million people who received the single-shot Johnson & Johnson vaccine.

While it’s good to know that a booster shot is safe, the question is whether it’s necessary. The decline in effectiveness against acute infection for the mRNA vaccines has been documented (although still robust against hospitalization and death). The data we have seen thus far on the J&J/Janssen vaccine suggests that the adenovirus-based vaccine holds up much better and longer even with a single shot:

Johnson & Johnson carried out its clinical trial before the Delta variant became widespread, leaving open the question of how well the vaccine worked against the highly contagious form of the virus. But in a study released earlier this month, South African researchers found that a single shot of the Johnson & Johnson vaccine was up to 95 percent effective against death from the Delta variant, and reduced the risk of hospitalization by 71 percent.

In its new study, Johnson & Johnson tracked 17 volunteers from last year’s clinical trial. Six months after vaccination, their level of antibodies had changed little.

That’s different than the pattern seen with the Moderna and Pfizer-BioNTech vaccines. Those shots initially produce higher levels of antibodies, but their levels then drop over several months.

Seventeen is hardly a conclusive study sample, of course, but we don’t have any data going the other way — showing any decline in effectiveness for J&J/Janssen. If that’s the case, are boosters necessary, even if they’re safe and “effective” in producing ninefold increases in antibody production? Antibody levels are the easiest immune response to measure, but it’s not the only immune response the body produces from infections or vaccines. T-cell response matters more and is the long-haul immunity that we hope all vaccines produce, not just those against COVID-19.

To put it in terms of the headline of this post: are we sure we really need two Death Stars if one is still fully armed and operational? Shouldn’t we focus more on getting the J&J/Janssen vaccine up to full production to get the unvaccinated covered with their first shot?

That brings us to another issue with the implications of this new study. The FDA and CDC all but destroyed the credibility of the J&J/Janssen vaccine, and then had to intervene when its production facility in the US turned out to be cross-contaminating it with the AstraZeneca vaccine. Where will the booster shots come from for the 14 million Americans who received their single-dose J&J/Janssen shot? How will those get distributed when they do get produced? I got mine nearly six months ago in Minnesota, but I’m now in Texas. I am certain that I won’t be the only person in that position, either.

As I have written before, I’m not opposed to getting a booster shot, which I assumed would eventually be necessary at some point. I’d like to make sure that it is necessary first, even though I’m relieved that it’s at least safe and provides a robust response. However, our public policy should be aimed at getting people to take their first shots of the J&J/Janssen vaccine rather than aiming at those who already have a robust immune response from their previous inoculation.