New York – Immunity gained after a natural infection is short-lived and remaining unvaccinated can increase the risk of getting re-infected with Covid-19, suggests a study published in the journal The Lancet Microbe. Lead author Jeffrey Townsend, Professor of Biostatistics at the Yale School of Public Health, said: “Re-infection can reasonably happen in three months or less. Therefore, those who have been naturally infected should get vaccinated. Previous infection alone can offer very little long-term protection against subsequent infections,” Townsend added. The team analysed known re-infection and immunological data from the close viral relatives of SARS-CoV-2 that cause “common colds” – along with immunological data from SARS-CoV-1 and Middle East Respiratory Syndrome. With evolutionary principles, the team was able to model the risk of Covid-19 re-infection over time.