Preventing SARS-CoV-2 superspreading events with antiviral intranasal sprays

Introduction

Superspreading events are known to disproportionally contribute to onwards transmission of epidemic and pandemic viruses. Preventing infections in a small number of high-transmission settings is therefore an attractive public health goal.

Methods

We use deterministic and stochastic mathematical modelling to quantify the impact of intranasal sprays in containing outbreaks at a confirmed superspreading event (the 2020 SARS-CoV-2 outbreak at the Diamond Princess cruise ship) and a conference event that led to extensive transmission.

Results

In the Diamond Princess cruise ship case study, there exists a 7–14-day window of opportunity for widespread prophylactic intranasal spray usage to significantly impact the number of infections averted. Given an immediate response to a known SARS-CoV-2 outbreak, alongside testing and social distancing measures, prophylactic efficacy and coverage greater than 65% could reduce the average number of infections by over 90%. In the conference case study, in the absence of additional public health interventions, analyses suggest much higher prophylactic efficacy and coverage is required to achieve a similar outcome on a population level. However, prophylactic use can halve an individual’s probability of being infected, and significantly reduce the probability of developing a severe infection.

Conclusions

At a known potential superspreading event, early use of intranasal sprays can complement quarantining measures and significantly suppress a SARS-CoV-2 outbreak, even at suboptimal coverage. At a potential superspreading event of short duration, intranasal sprays can reduce individuals’ risk of infection, but in the absence of other interventions, they cannot prevent all infections or all onwards community transmission.

Plain language summary

Where crowds are in close contact in closed spaces, respiratory viruses like coronavirus spread easily. At such events, superspreading may occur: one person transmitting the virus to many other event-goers, fuelling the epidemic or pandemic. We used mathematical modelling to predict whether antiviral nose sprays which act immediately can prevent such superspreading events. We found that early use of nose sprays can suppress a SARS-CoV-2 outbreak, even if not everybody is treated with the nose spray, as long as people are also tested and use social distancing if infected. At a conference where people do not quarantine, it is more difficult to prevent spreading of the virus altogether with nose sprays alone. However, at an individual level, people who take the nose spray have lower chance of getting infected with the virus.