I'm sure this will be viewed as a "dumb" question about the boosters...

[hlthe2b]

2. When you say serum, that refers to serum antibody treatments. Vaccine are innocolations

of (in the case of mRNA vaccines) of a small bit of mRN developed to stimulate both your b-cells to produce antibodies and your T-cells to gear up a generalized protective response. Vaccine-induced immunity is relatively long-livd depending on the infectious agent to which it is targeted--obviously impacted by new variants emerging. The monoclonal antibody treatments (that appear to have confused you, confer no (zero) long term immunity but help fight an ongoing infection).

There is considerable doubt that the degree of reduction for Pfizer against DELTA shown by one pre-print and non peer-reviewed study is valid, but even if it is, receipt of either Pfizer or Moderna mRNA vaccine will stimulate a boosted immune response. Pfizer has data showing it increases at least 10x in otherwise healthy populations.

Boosted immune response will help against infection break-through but as you should know by now, the emphasis is on preventing severe disease and death. Both vaccines already do so, but that effectiveness should be boosted dramatically as well.