Although the difficulties posed from developing efficacious vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may seemingly be surmounted, the next difficult task will be to effectively distribute the vaccine and convince sufficient numbers of individuals to be vaccinated in order for herd immunity to be successful. This comment was published in The Lancet.

There are currently several dozen candidate vaccines for coronavirus disease 2019 (COVID-19) in clinical trials, 10 of which are in phase 3 and anticipate releasing preliminary results by the end of 2020. Widespread distribution may begin in mid to late 2021, given positive results. For any successful vaccination plan to be effective, the development of a distribution structure is needed alongside a program which encourages participation.

The comment authors speculated about which individuals should be targeted vaccine recipients, following front-line workers. Is the goal of the COVID-19 vaccination program to minimize net mortality or to maximize years of life gained?

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Using data from the United Kingdom, the authors estimated that prioritizing individuals aged 70 years or older would save more lives than targeting adults aged 50-70 years. The authors recommended governments to prioritize mortality minimization during the short term. However, if the vaccine supply is not sufficient to protect the population for a minimum of 1 year, it remains unclear whether an older population would be the most prudent primary recipients.

Much about the SARS-CoV-2 vaccination program is poorly understood, including the time it will take to manufacture sufficient supply or how long immunity will last after vaccination.

Regardless, the distribution of vaccines will likely be a slow process due to manufacturing time. The authors estimated that a large proportion of the population must be vaccinated during the first year in order for herd immunity to be achieved and to protect against continued SARS-CoV-2 infections.

The comment authors concluded that if countries do not reach a sufficiently high proportion of vaccinated individuals, SARS-CoV-2 will become endemic at low levels and will likely peak during colder months.


Anderson RM, Vegvari C, Truscott J, Collyer BS. Challenges in creating herd immunity to SARS-CoV-2 infection by mass vaccination. Lancet. 2020;396(10263):1614-1616. doi:10.1016/S0140-6736(20)32318-7.