Success And Challenges In Mass Screening For Covid-19 Control: The Andorra Story
Once again, Andorra is setting a global standard for Covid-19 testing. The small European nation undertook a mass SARS-CoV-2 serological screening during its first wave, making it the first and most comprehensive seroprevalence study of its kind in the world, assessing the whole population of a country. This begs the question is testing enough to help control a pandemic?
Andorra is a small country in the Pyrenees that attracts millions of tourists, primarily for skiing and other outdoor activities. It has been severely impacted by the pandemic, as have its neighboring countries, Spain and France. The country has always had rigorous testing programs, among which was a nationwide distribution of rapid antigen tests to all residents over the age of six last December. Yet Andorra is proof that testing is not enough and needs to be followed up with efficient contact tracing and isolation.
All of Andorra’s population was invited to participate in the mass screening through television and social media advertisements. Almost 91 percent voluntarily participated in at least one of two cross-sectional serological surveys that were conducted in 59 drive-through or walk-through checkpoints in Andorra, using a fast serological test on a finger prick blood sample. The screening took place over the span of a little over three weeks in May 2020, with the second survey taking place four days after the end of the first. At the time, the country had been in lockdown since mid-March, with borders being heavily restricted, only allowing essential workers to enter from neighboring countries.
Overall seroprevalence was 11%, and was highest in older age groups, as well as seasonal workers and families with larger households. Researchers also recorded a decrease in seroprevalence between the two surveys, which they claim to be largely due to a decrease in antibodies in asymptomatic patients over time, as antibody levels decline early after infection and could have been at undetectable levels during the second survey.
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While the study does have some limitations, such as the fact that the epidemiological situation has drastically changed since the first wave, researchers are confident that the study helped pinpoint infection hotspots and will aid in the development of targeted measures to prevent SARS-CoV-2 spread in Andorra.
Andorra has accumulated over 17,000 cases per 100,000 people since the pandemic began. That is more than France and Spain combined, who have reported around 8,500 and 7,900 cases per 100,000 respectively. This does not mean that Andorra performed worse than its neighboring countries when trying to contain the virus, but rather that testing rates were much higher. When looking at the number of SARS-CoV-2 tests performed, Andorra carried out nearly 2,500 tests per 1,000 inhabitants. Comparatively, Spain has not yet reached 1,000 tests per 1,000 people. Andorra was thus left with a much better understanding of its infection rates, and was able to detect asymptomatic cases.
The strategy, however, was not successful as a Covid control tool. Andorra’s cumulative death count is very close to that of France’s and Spain’s, which had much less rigorous testing regimes, with about 164 deaths per 100,000 inhabitants. The amount of information that Andorra has accumulated and hopefully will continue to amass, has put the country in a better position to control future waves if a systematic program is put in place. Testing must be combined with efficient contact tracing and mandatory isolation. Countries that follow this program will not only know how the virus will spread among their population, but will be able to control it.