I don’t understand why you think that follows from that passage. I interpret it to mean serial exposure to a series of variant-specific vaccines may reduce overall effectiveness. e.g. Imagining a hypothetical variant sequence of V → V’ → V″. I interpret this as saying if you vaccinate for each with a variant-specific vaccine the effectiveness of the V″ vaccine will be less effective than the original vaccine was for V. Therefore they theorize it may be advantageous to break the chain and e.g. give half the people the V’ vaccine when available while the other half skips V’ and is given V″ vaccine when available.
Their reasoning isn’t entirely clear to me since it’s not clear to me exactly how and by what mechanism(s) the vaccine effectiveness may degrade.
FWIW, there is other SARS2-specific supporting evidence that immune imprinting may be an issue for vaccine updates. Lately in the UK Health Security Agency weekly vaccine surveillance reports they have begun including this note:
>(iii) recent observations from UK Health Security Agency (UKHSA) surveillance data that N antibody levels appear to be lower in individuals who acquire infection following 2 doses of vaccination.
(From page 39 paragraph 3 of https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1036047/Vaccine_surveillance_report_-_week_47.pdf)
The UK tracks seropositivity of S and N antibodies. N antibody positivity is used to track the subset of people who were previously infected. This note implies the immune system may not be updating its response when challenged with a new variant of the live virus.