There are several potential reasons that memory B cells produced by natural infection might be expected to outperform those produced by mRNA vaccines, the researchers say.
It is possible that the body responds differently to viruses that enter through the respiratory tract than those that are injected into our upper arms. Or perhaps an intact virus goads the immune system in a way that the lone spike protein represented by the vaccines simply cannot. Then again, maybe it’s that the virus persists in the naturally infected for weeks, giving the body more time to mount a robust response. The vaccine, on the other hand, is flushed out of the body mere days after triggering the desired immune response.
Regardless of the cause, the implications are clear. We can expect memory B cells to undergo limited volleys of evolution in response to mRNA vaccines, a finding that may have significant implications for the design and rollout of booster shots. A booster with the currently available mRNA vaccine would be expected to engage memory cells to produce circulating antibodies that are strongly protective against the original virus and somewhat less so against the variants, Nussenzweig says.