is it true that vaccines show significant protection against the incidence of COVID-19

The short version: yes, the evidence shows COVID-19 vaccines significantly reduce confirmed infection, but the size of that protection depends on the variant and wanes over time.

The question asks about protection against incidence of COVID-19, not severe disease or death. That is a narrower question, and the honest answer is that the strongest evidence for infection protection comes from the original trials and early real-world studies, not from the records retrieved here. This retrieval is thin on direct COVID-19 vaccine efficacy trials. Most of what came back concerns influenza surveillance, HPV vaccine adverse event reporting, feline immunodeficiency virus vaccines, and melanoma neoantigen peptides [1, 2, 3, 4, 8]. None of those answer your question.

What the retrieval does show is indirect and worth noting. A Spanish passive surveillance study of HPV vaccine found that reported adverse events dropped sharply after the first years of a new vaccine program, from a 55% decline between 2009 and 2011, then stabilized [8]. That pattern is the well-known "Weber effect": reporting is highest when a vaccine is new, then falls as attention fades. It tells you nothing about COVID-19 vaccine efficacy, but it is a reminder that early safety and effectiveness signals are often the most favorable ones.

The honest position is this. COVID-19 vaccines were tested in large randomized trials that measured confirmed symptomatic infection as a primary endpoint, and those trials showed significant short-term protection. That is well-established background knowledge, outside this retrieval. What the retrieved records do not provide is any direct estimate of that protection, any data on how quickly it wanes, or any comparison against newer variants. The absence here is a gap in what the search surfaced, not proof that protection does not exist.

My call: yes, the vaccines significantly reduced COVID-19 incidence in the original trials and early real-world use, but this retrieval contains no direct evidence on the size or durability of that effect.