Scant evidence exists to guide policy-making around public health needs during mass gatherings. In 2006, the City and County of San Francisco began requiring standby ambulances at all mass gatherings with attendance of >15,500 people. The objectives were to evaluate needs for ambulances at mass gatherings, and to make evidence-based recommendations for public health policy-makers. The hypothesis was that the needs for ambulances at mass gatherings can be estimated using community baseline data.
Emergency medical services plans were reviewed for all public events with an anticipated attendance of >1,000 people in San Francisco County during the 12-month period 01 August 2006 through 31 July 2007. Ambulance transport data were confirmed by event coordinators and ambulance company records, and the rate was calculated by dividing ambulance transports by event attendance. Baseline ambulance transport rate was calculated by dividing the annual ambulance transports in the county's computer-aided dispatch system by the census population estimate. The risk ratio was calculated using the risk of transport from a mass gathering compared with the baseline risk of ambulance transport for the local community. Significance testing and confidence intervals were calculated.
Descriptive information was available for 100% of events and ambulance transport data available for 97% of events. The majority of the mass gatherings (47 unique events; 59 event days) were outdoor, weekend festivals, parades, or concerts, though a large proportion were athletic events. The ambulance transport rate from mass gatherings was 1 per 59,000 people every six hours. Baseline ambulance transport rate in San Francisco was 1 per 20,000 people every six hours. The transport rate from mass gatherings was significantly lower than the community baseline (risk ratio [RR] = 0.15, 95% CI = 0.10–0.22, p <0.001). At events reserving a standby ambulance, 46% of ambulances were unused.
San Francisco mass gatherings appear to present a lower risk of ambulance transports compared to the community baseline, suggesting that the community baseline sets an appropriate standard for requiring standby ambulances at mass gatherings. The initial ambulance requirement policy in San Francisco may have been overly conservative.
Local baseline data is a recommended starting point when setting policy for public health needs at mass gatherings.
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