London: People previously infected with the SARS-CoV-2 virus still benefit from vaccination against COVID-19, gaining 60 per cent to 94 per cent protection against reinfection, according to a study. The research, published in the journal PLOS Medicine, analysed infection and vaccination data from nationwide Danish registers. The data included all people living in Denmark who tested positive for the virus or were vaccinated between January 2020 and January 2022.
The researchers at Statens Serum Institut, Denmark, analysed more than 200,000 people who tested positive for SARS-CoV-2 during each of the Alpha, Delta and Omicron waves. Their findings show that for people with previous infections, vaccination offered up to 71 per cent protection against reinfection during the Alpha period, 94 per cent during the Delta period and 60 per cent during the Omicron period, with protection lasting up to nine months.
In our study we find a significant vaccine effectiveness against SARS-CoV-2 reinfection, and this shows the importance of vaccination also for those who might be protected by natural immunity," said Katrine Finderup Nielsen from Statens Serum Institut. These findings show vaccination protected people against SARS-CoV-2, over and above the protection offered by natural immunity during all three waves of variants.