Why Johnson & Johnson’s one-shot Covid-19 vaccine is a game changer

One big reason to be excited about the new Johnson & Johnson vaccine for Covid-19, which was authorized by the Food and Drug Administration over the weekend for emergency use in the US: Unlike the Moderna and Pfizer vaccines already in use, it requires only one shot for full protection.

That’s a big deal. From a practical standpoint, it means that the new vaccine could really speed up America’s vaccination campaign — certainly more than another two-dose vaccine would. It also fixes a problem that’s long bedeviled medical treatments that require multiple doses: A lot of patients tend to drop off after the first appointment.

“Especially when you’re trying to think about a massive public health program like this vaccine rollout, a single-dose vaccine would have made it much, much simpler” if it were the first to get approval, Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, told me.

Some have been skeptical of the Johnson & Johnson vaccine because the reported data on its efficacy was lower than that from the Moderna and Pfizer vaccines. Initially, the vaccine was reported at 66 percent effectiveness against Covid-19, which paled in comparison to 90-plus percent for the other two authorized vaccines.

But in many ways, that’s looking at the wrong number. The vaccine’s effectiveness at preventing people from getting sick with symptoms is arguably much less important than the vaccine’s effectiveness against hospitalization and death. And there is the promising news: In trials, the Johnson & Johnson vaccine brings both of those down to zero. It squashes the biggest thing that made Covid-19 so threatening to people: its ability to kill.

Given the ongoing supply constraints and high demand, experts say people should get whichever vaccine is first available to them — that’s how we’ll beat Covid-19 as quickly as possible.

But for people who are bad at follow-up appointments (including me) and from a broader public health perspective where speeding and smoothing the vaccine rollout is crucial, the Johnson & Johnson vaccine and other one-shot inoculations are genuine game changers.