Counts of reported cases have been the key metric to monitoring the COVID-19 pandemic. However, since the beginning, it has been clear that reported cases represent only a fraction of all SARS-CoV-2 infections. Despite reported cases acting as the key metric for understanding the far-reaching implications of the COVID-19 pandemic, it has always been clear that these represent merely a portion of all SARS-CoV-2 infections. This interesting short review published on the Lancet uses a new approach to calculate the proposed global number of infections and includes combined data from reported cases, deaths, excess deaths attributable to COVID-19, hospitalizations, and seroprevalence surveys. The aim is to produce broader estimates while reducing biases inherent in them.  

“According to COVID-19 Cumulative Infection Collaborators findings, a staggering number of people, 3·39 billion (95% uncertainty interval 3·08–3·63) or 43·9% (39·9–46·9) of the global population, are estimated to have been infected one or more times between March 2020, and November 2021. Remarkably, this was before the highly transmissible Omicron (B.1.1.529) variant swept the globe. These estimates of total infections are wildly different from the number of reported cases, which stood at 254 million as of Nov 14, 2021. As such, one could argue that the proportion of the people ever infected is no longer a meaningful metric of population immunity. However, the same data streams to infer that cumulative incidence can be used to address more pressing epidemiological questions, such as- How severe are new variants? To what extent do the population’s historical infections—in terms of timing and variants—protect against infection and severe disease of new variants? Relatedly, how do layers of vaccine-induced and virus-induced immunity combine to confer protection to the population?”1

References

  1. Shioda, K., & Lopman, B. (2022). How to interpret the total number of SARS-CoV-2 infections. The Lancet, 399(10344), 2326–2327. https://doi.org/10.1016/s0140-6736(22)00629-8

Disclaimers

  • The material in these reviews is from various public open access sources, meant for educational and informational purposes only
  • Any personal opinions expressed are those of only the author(s) and are not intended to represent the position of any organization(s)
  • No official support by any organization(s) has been provided or should be inferred