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Research suggests limited risk of COVID-19 transmission from mass gatherings

Rod Tucker
29 June, 2021  

Data suggests limited rates of COVID-19 transmission from mass-gathering events involving thousands of people.

A research programme established to determine the extent of COVID-19 transmission with both indoor and outdoor events without social distancing has been published by the UK government. Many mass gathering events such as music festivals, theatres and both indoor and outdoor sporting events were cancelled because of the risk of COVID-19 transmission. As a result, a primary aim of the research, which was conducted on behalf of the UK government, was to obtain an evidence base of the risks associated with COVID-19 transmission at large public events and to hopefully reassure members of the public that it was safe to return to such large-scale events. The first phase of the research consisted of nine pilot events running across multiple days in April and May 2021 and in a variety of outdoor and indoor venues. Each of the pilot sites examined variations in the seating, standing and the structure of the audience and participant numbers. The data captured by researchers was not restricted to transmission of COVID-19 but included monitoring of ventilation, analysis of carbon dioxide and crowd density as a proxy for airborne transmission, observing and analysing crowd behaviour, interviews and surveys with participants. Events included the World Snooker Championship, with 10,147 individuals seated indoors at which social distancing was required for the first five days but dropped for the final although face coverings were mandated at all times. Several football matches were also included and whilst the crowds were outdoors, as with the indoor events, face coverings were required. However, for some events such as one held at a nightclub over two consecutive evenings, with over 3000 people, no social distancing or face coverings were required. Similarly, an outdoor music festival with just over 6000 people there was no requirement for either social distancing or face covering. In addition, all participants were required to have a negative lateral flow test result within 36 hours of the event to be permitted to enter the venue. In addition, PCR testing prior to the event was a voluntary rather than mandatory requirement though it could also be undertaken on the day of the event. Moreover, participants were posted a home PCR test to be used five days later were also used to identify subsequent cases.

Findings
The results showed that there was limited evidence of COVID-19 transmission across all events with only 28 PCR-positive test results recorded, with 11 considered potentially infected before the event. Nevertheless, there were some important caveats with the data. Firstly, the return rate of PCR tests was low, ranging from 8% to 74% before the event to 13% to 66% post-event, hence limiting the estimate of infectivity rates. A further limitation of the data was the during the period of the pilot study estimates of infection rates in the community were low and prior to the emergence of the Delta COVID-19 variant of concern. An operational learning from the pilot was that the current contact tracing infrastructure is not designed for testing at events with large numbers of people.

Although the early results from the pilot are encouraging and inline with other studies and suggest that during mass gathering events there appears to be limited COVID-19 transmission, it should be emphasised that the data are limited because it was based on only a small number who returned their PCR test results.

Events research programme 2021