We know from laboratory studies that having a booster on top of the regular vaccine series dramatically increases the level of neutralizing antibodies that individuals have. And, at least preliminarily, that is translating into the incoming clinical evidence that it protects against infection and against disease to a significantly greater extent than does the initial vaccine series.

The central question is what do we want from these vaccines. If what we want from these vaccines is protection against serious illness—meaning the kind of illness that causes you to go to a doctor, go to the hospital, go to the intensive care unit—it looks for all the world like two doses of these mRNA vaccines, Pfizer, Moderna, protects against serious illness. However, protection against mild illness does not appear to be as good with two doses of vaccine against the omicron variant. So there you could argue that if you wanted to be protected additionally against mild or low/moderate illness, it makes sense to get a booster dose.

Some early studies—one in particular that just came out—seem to indicate that boosting is not providing the level of protection we’d like to see against omicron, and that people’s neutralizing antibodies are compromised in fighting off infection from the omicron variant. That said, neutralizing antibodies are not the whole picture. There are other components of the immune system, such as reactive T cells, memory B cells, that are important portions of it that may actually support a more effective immune response. We don’t know. That’s the answer right now. But we’re concerned.