Findings from Brazil, Sweden and the United Kingdom show that before the advent of Omicron, vaccination benefited even those who had had a bout of COVID-19.
. Peter Nordström, an epidemiologist at Umeå University in Sweden, says this dichotomy prompted him and his colleagues to perform another of the studies.
Although vaccination increases protection, Nordström thinks the immunity offered by infection alone is worthy of consideration. “Perhaps we should have immunity passports instead of vaccination passports. So you are considered immune — and less likely to transmit the disease — if you have been fully vaccinated, or you have had a documented previous infection,” he says.
Dan Kelly, an infectious-disease epidemiologist at the University of California, San Francisco, underscores that concern. Omicron is so different from the strains analysed in the studies that the findings might not apply to people who were infected with Omicron after being vaccinated. His advice to people who fall into this category: “Just be really careful.”