KARACHI: Although people who recover from COVID-19 usually gain some immune defences against reinfection, they get additional protection from vaccines, especially against severe diseases, according to two studies published on Thursday in The Lancet Infectious Diseases.
In a study of 22,566 persons in Brazil who had recovered from COVID, researchers discovered that all four vaccinations are now in use – from Sinovac Biotech, AstraZeneca, Johnson & Johnson, and Pfizer/BioNTech – gave considerable extra protection. The effectiveness of the Sinovac CoronaVac vaccine against infection 14 days after completion ranged from 39.4 per cent to 64.8 per cent for the Pfizer/BioNTech doses. CoronaVac's effectiveness against hospitalisation or death was 81.3 per cent, while Pfizer/vaccine BioNTech's was 89.7 per cent.
The second study, which included data from more than 5 million people in Sweden, discovered that "hybrid immunity" resulting from a combination of past infection and one or two vaccination doses gave increased protection for at least nine months. Compared to natural immunity alone, "one-dose hybrid immunity was related with an extra 94 per cent lower risk of COVID-19 hospitalisation, and two-dose hybrid immunity was associated with an additional 90 per cent lower risk COVID-19 hospitalisation," the researchers wrote. Patients infected or reinfected with the Omicron variant were excluded from either study.
