Small study (52 people) indicates that breakthrough COVID infections, not including omicron, in the fully vaccinated results in high levels of neutralizing antibodies.

Medical Mythbusting Commentary for December 21, 2021

Source:
Breakthrough infection could mean ‘end game’ for COVID

‘Super Immunity’ From Breakthrough Infection After Covid-19 Vaccination? Here’s What This Study Said

Reference:
Antibody Response and Variant Cross-Neutralization After SARS-CoV-2 Breakthrough Infection