The effectiveness of non-pharmaceutical interventions in containing epidemics: a rapid review of the literature and quantitative assessment

Jane Cheatley; Sabine Vuik; Marion Devaux; Stefano Scarpetta; Mark Pearson; Francesca Colombo; Michele Cecchini

There is limited data on the effectiveness of contact tracing and quarantine. Evidence that is available is largely based on modelling studies, which suggest quarantine decreases the peak case load, the attack rate and would also delay the peak. Household quarantine is potentially the most effective measure to reduce attack rates in the community, but only if compliance is high (Rashid et al., 2015[5] ). Voluntary or self-isolation of infected people is moderately effective. For instance, voluntary quarantine of households with an infected individual may delay the peak of influenza by two to 26 days, and reduce the peak daily attack rate from 1.9% to 1.5%, or even down to 0.1%, depending on the associated interventions (e.g. such as treating infected people and applying prophylaxis to their households the day after the symptoms start, school closure) (Ferguson et al., 2006[14] ). Modelling work simulating the isolation of cases and contacts in the case of the COVID-19 pandemic concluded that about 70% of cases had to be traced to successfully contain the outbreak, assuming a reproduction number of 2.5 (Hellewell et al., 2020[29] ). Implementation of contact tracing and quarantine measures bears economic costs, and is associated with psychological, legal, and ethical issues. First, contact tracing requires substantial resources to sustain after the early phase of the epidemic since the number of infected people and contacts grow exponentially. While there is no obvious rationale for a routine use of contact tracing in the general population, it may be adapted in some circumstances (e.g. if there was an infected person on an aircraft) (Fong et al., 2020 [31] ). In addition, isolation is likely to cause distress and mental health problems, requiring additional services such as creating support lines and advice, helping people create plans, encouraging messages and calls and maintaining some routine (Lunn et al., 2020 [32] ).