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New study co-authored by CU Boulder economist evaluates the costs and benefits of stricter social distancing policies when a U.S. vaccine arrival is imminent

To reduce total number of deaths, strict social distancing policies are still best, new from three economists suggests. 

That is only because the COVID-19 vaccines have been created and distributed quickly in the United States. If the vaccines had taken longer to develop, however, a looser public policy might have made more sense, they also found.

Alessandro Peri

The authors, who include Alessandro Peri, assistant professor of economics at the University of Colorado Boulder, evaluate different social-distancing policies, including the , which recommends striving to attain herd immunity quickly by forgoing much social-distancing. 

The research appeared in , a journal published by the University of California Giannini Foundation of Agricultural Economics and found that, particularly when people expect an early vaccine arrival, a policy promoting quick herd immunity leads to much higher combined economic and mortality costs, compared to the optimal social-distancing policy.

Since the COVID-19 pandemic hit last year, policymakers have faced difficult choices: Which social distancing policies should be implemented, and how long should they remain in place? 

While stricter policies reduce the spread of the virus and thus decrease initial mortality and the costs associated with increased cases of infection in the present, they also have both economic and social costs over time, the researchers say. 

How these policies affect society also depends on estimates of “vaccine arrival,” the time to develop and widely distribute a vaccine to the extent that social distancing policy is no longer needed.

To evaluate the costs and benefits of stringent social distancing policy with varying estimates for vaccine arrival time, the researchers used a modified version of a mathematical model used widely in epidemiology, the Susceptible-Infected-Recovered (SIR) model. 

The researchers suggest that optimism generated by an early vaccine arrival works well with strict social distancing. But they say mathematical models such as SIR “can discipline our attempt to answer such questions, helping to distinguish internally consistent and empirically grounded analysis from a merely plausible story.”

This model assesses the population as a network of individuals who start as initially susceptible. It then shows how the individuals within the population move from infected to recovered within the bounds of parameters such as different social-distancing policies, and it forecasts how these choices affect the population as a whole. 

These models help assess the benefits of reducing infection in the present with the risk of having more susceptible people in the future because these people did not move from “infected” to “recovered” early in the model. 

Modeling the different policy and vaccine arrival scenarios led the researchers to conclude that the optimal policy in the current U.S. context involves a stricter social distancing policy, since vaccines have arrived much sooner than previously expected and are now being distributed.

The paper also evaluates proposals to move quickly to herd immunity by allowing those less vulnerable to the disease to have no restrictions. The economic and mortality costs under that policy are compared to the costs under both an optimal uniform policy (where all are subject to the same social distancing policy) and an optimal targeted policy (where different risk groups face different social distancing requirements). 

The authors determined that if the vaccine arrival were still two years out, the optimal uniform policy only slightly outperforms the proposal that seeks rapid herd immunity by dropping most social distancing requirements. 

However, they found that for a vaccine that arrives within six months of an outbreak, the economic and mortality costs of moving quickly to herd immunity exceed the cost under either optimal uniform or optimal targeted policy by $3 trillion—with an estimated 520,000 more deaths from those 65 years old and over and 380,000 deaths of the less vulnerable group, under 65. 

Peri’s co-authors are Terrence Iverson, associate professor of economics at Colorado State University, and Larry Karp, professor of agricultural and resource economics at the University of California, Berkeley.