Study: Previous COVID-19 infection offers protection against BA.5Infections with previous COVID-19 variants offer more protection against the Omicron BA.5 subvariant in vaccinated people compared with vaccinated people who had no previous infections, according to a New England Journal of Medicine study yesterday.The study was based on research conducted at the University of Lisbon in Portugal and is among the first studies to analyze protection against BA.5 among vaccinated and naturally infected people.
The authors used the Portuguese national registry of COVID-19 cases to determine which variant likely caused infection based on date and variant predominance.
Cases in patients age 12 and older were used.The researchers found that while natural infections from 2020 and 2021 (when the wild-type strain and the Delta variant were predominant) offered some protection again BA.5, people infected with the BA.1 and BA.2 variants, at the beginning of 2022, who were also vaccinated had four times the protection as those who were only vaccinated."This study demonstrates, in the period of time analysed, that previous infection in vaccinated people (the so-called hybrid immunity) continues to confer for the variants that are known for their ability to evade the immune response, such as the subvariant currently dominant," said Valter Fonseca, MD, PhD, co-author of the study, in a press release from the Instituto de Medicina Molecular at the University of Lisbon.The authors said their findings challenge the perception that protection afforded by previous BA.1 or BA.2 infection is very low."Our data indicate that this perception is probably a consequence of the larger pool of persons with BA.1 or BA.2 infection than with infection by