643 million already infected by Covid-19 globally: Seroprevalence meta-analysis

A meta-analysis carried out by a team of international researchers revealed low seroprevalence of SARS-CoV-2 antibodies in the general public.

Since the beginning of the Covid-19 pandemic in December 2019, the highly infectious SARS-CoV-2 has infected more than 56.5 million people and claimed more than 1.35 million lives worldwide.

However, according to the study published in the journal medRxiv, the exact global prevalence of the SARS-CoV-2 infection seems to be higher than the reported prevalence.

Moreover, an increased prevalence of asymptomatic cases could be another important reason for such underestimated Covid-19 cases.

Methodology

For the study, the researchers included peer-reviewed articles, preprint articles, and other non-commercial/non-academic articles that were published between January 1 and August 28, 2020.

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A total of 338 seroepidemiological studies were analysed involving 2.3 million individuals from 50 countries.

They also employed various statistical analytical methods to identify demographic differences in seroprevalence.

Findings

The findings revealed that the SARS-CoV-2 antibody seroprevalence was as low as 3.2 per cent in the general population. Similarly, the seroprevalence was 5.4 per cent in at-risk populations (special populations).

As for frontline workers, anti-SARS-CoV-2 antibodies were detected in 6.3 per cent and 10 per cent of healthcare workers and essential non-healthcare workers respectively.

Compared to the general population, healthcare workers were 1.7 times more likely to be seropositive. Similarly, people with established contact exposure were also susceptible to develop anti-SARS-CoV-2 antibodies.

A comparatively lower seroprevalence was observed in high-income countries (3.4 per cent). Despite having a higher risk of SARS-CoV-2 transmission and poor Covid-19 prognosis, the number of studies conducted in low- and middle-income countries was low (25 per cent).

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On demographic characteristics, a higher seroprevalence is observed in people aged 18 to 64 years, compared to those ages 65 years and above.

White people were less likely to have anti-SARS-CoV-2 antibodies than black people and Asian people.

Notably, the authors of the study further pointed out that about 643 million people may have already been infected by the virus globally. This is much more than the reported Covid-19 cases (currently 56.5 million).

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