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The advantages of quick antigen tests

Testing of people infected by SARS-CoV-2 and tracking of contacts allows more appropriate public health precautions to be put in place, but is usually insufficient to inhibit the virus’ spreading. Amongst existing diagnostic methods, PCR testing is the benchmark, but is limited by the capacities of laboratories, the cost of the test, and the waiting time for results, usually more than 24 hours. On the other hand, antigen tests are more adapted to mass testing since they can be manufactured in huge quantities, are inexpensive and give a result in less than 30 minutes. However, they are much less sensitive and only allow around 70% of infections to be detected. Slovakian researchers and scientists at the London School of Hygiene and Tropical Medicine have evaluated the impact of mass rapid-testing, carried out in Slovakia, on the transmission of the virus across the country.

Slovakia carried out several mass antigen test operations in October and November 2020: a pilot study over 4 regions, then a national campaign, and then a second campaign 7 days later in the most affected regions. In total, more than 5 million rapid antigen tests were performed.

The proportion of positive cases was around 4% in the localised pilot operation, 1% in the national campaign that followed and 0,6% in the second regional campaign. The highest rates of infection were observed in young people and in less-populated regions. Whereas the growth rate of the epidemic was at more than 4% per day before the mass-testing initiatives, the reduction in the number of infections was estimated to be 91% over 3 weeks in the 4 regions that participated in the pilot campaign and in the national campaign. In the 41 regions that participated only in the national campaign, the reduction was 81% in 2 weeks. It must be noted, however, that it is difficult to separate the effects of mass testing from other sanitary measures  put in place during this period. However, by way of comparison, the month-long UK lockdown in November led to a reduction in the number of infections of only 30%.

In conclusion, the combination of mass-testing campaigns, of isolation of infected individuals and of a contact tracking system in Slovenia led to a drastic reduction in the epidemic’s incidence. Rapid antigen testing, although less sensitive than PCR tests, provided numerous advantages for mass-testing.

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