Global COVID-19 infection rates may far exceed previously reported cases because routine surveillance underestimates them, a World Health Organization-led study says. File Photo by Jim Ruymen/UPI | License Photo
Nov. 10 (UPI) -- Global COVID-19 infection rates may far exceed previously reported cases because routine surveillance underestimates them. That suggests a bigger global impact from the pandemic, a World Health Organization-led study released Thursday says.
An international research team conducted a new meta-analysis, which included a review of 965 population-based studies, to estimate the proportion of the global population with antibodies against SARS-CoV-2, the virus causing COVID-19.
Using this approach, the scientists calculated that global "seroprevalence" -- defined as the level of a pathogen in a population, as measured in blood serum -- increased to 59.2% by September 2021, up from 7.7% in June 2020.
In other words, although global seroprevalence rose considerably over time, more than one-third of the global population remain seronegative -- lacking antibodies to the virus.
The researchers said it's important to continue investing in such "serosurveillance" to better monitor the COVID-19 pandemic and prepare for potential emerging viruses.
According to the scientists, a basic understanding of the global scale of SARS-CoV-2 infection has been lacking because of "a predominance of asymptomatic infections, and uneven access to diagnostics" that routine surveillance cannot take into account.
Under the new analysis, the reviewed studies together covered a sample of 5.35 million participants, 41% of them from low- and middle-income countries, between January 2020 and April 2022.
Overall seroprevalence rose steeply in 2021 due to infection in some regions. It increased, for example, from 26.6% to 86.7% in Africa by December 2021, the researchers said in their paper.
And seroprevalence increased due to vaccination and infection in other regions, rising, for example, from 9.6% in June 2020 to 95.9% in December 2021 in European high-income countries.
After the emergence of the Omicron variant in March 2022, infection-induced seroprevalence rose to 47.9% in European high-income countries and up to 33.7% in high-income countries in the Americas, the investigators found.
The scientists acknowledged the study's limitations, such as underrepresentation of some countries in the data, and overrepresentation of other countries.