HealthDay News — Seroprevalence to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) increased sharply in 2021, according to research published online Nov. 10 in PLOS Medicine.
Isabel Bergeri, from the World Health Organization in Geneva, and colleagues estimated the extent of population infection and seropositivity to SARS-CoV-2 two years into the pandemic by meta-analyzing SARS-CoV-2 seroprevalence studies. A total of 513 full texts reporting 965 distinct seroprevalence studies sampling 5,346,069 participants between January 2020 and April 2022 were included.
The researchers found that the global SARS-CoV-2 seroprevalence from infection or vaccination was 59.2 percent by September 2021. There was a sharp increase in overall seroprevalence in 2021, due to infection in some regions (e.g., 26.6 to 86.7 percent in December 2021 in Africa) and vaccination and infection in others (9.6 percent in June 2020 to 95.9 percent in December 2021 in European high-income countries [HICs]). Infection-induced seroprevalence increased to 47.9 and 33.7 percent in European and American HICs, respectively, after the emergence of omicron in March 2022. The risk for seroprevalence was lower for children aged 0 to 9 years and adults aged 60 years or older compared with adults aged 20 to 29 years. Stringent public health and social measures were associated with lower seroprevalence in a multivariable model.
“Our results show that seroprevalence has increased considerably over time, particularly from late 2021, due to mainly infection in some regions and vaccination in others,” the authors write. “Nevertheless, there is regional variation and over one-third of the global population are seronegative to the SARS-CoV-2 virus.”
Several authors disclosed financial ties to the pharmaceutical industry.