In term of protection. For starters, if vaccine effectiveness were holding, there would be no need for boosters.
A picture from a recent preprint of 600k veterans over 6 months shows troubling VE against infection curves. J&J VE against infection is gone. Pfizer curve is just 2 months behind, at 53% and dropping.
https://www.medrxiv.org/content/medrxiv/early/2021/10/14/202...
https://www.medrxiv.org/content/10.1101/2021.10.13.21264966v...
Fortunately VE against severe infection holds much better at 77% Pfizer for June-Sept 2021 time period. The clinical trials claimed 94%, so there is a drop there. Nobody knows what will be the VE against sever infection a year from now, and we appear to have decided to preemptively boost so we might never know.
https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7037e2-H.pdf
https://www.pfizer.com/news/press-release/press-release-deta...
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Alas, none of this takes in account future virus variants and their interaction with OAS. OAS means that building an immune response against the virus today will prove ineffective for a virus variant 10 years down the line. The worst known scenario was encountered with dengue fever. An excerpt from a 2011 paper summarizing the dengue situation:
"Original antigenic sin has the advantage that a response can be rapidly mobilized from memory. However, the downside is that in some cases, such as dengue, the response is dominated by inferior-quality antibody. In influenza, original antigenic sin has been shown to reduce the effectiveness of vaccination (13, 34, 51). In dengue, the effect of original antigenic sin has considerable bearing on vaccine strategies. Once a response has been established, it is unlikely that repeat boosting will be able to change its scope, meaning that balanced responses against the four virus serotypes will need to be established with the first vaccine dose."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3014204