Single dose of the vaccine may be better than nothing at all

Researchers from Yale School of Public Health used a previously published model of a COVID-19 vaccination program to quantify the speed-versus-efficacy tradeoff of vaccination deployment. The model accounted for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), COVID-19 disease severity, and recovery or vaccination leading to protective immunity. According to the authors’ analysis, a 2-dose vaccination strategy would impose steep clinical and epidemiologic costs in the context of ongoing pandemic response. Depending on the duration of protection conferred, a single-dose vaccine with 55% effectiveness may confer greater population benefit than a 95%-effective vaccine requiring two doses.

Authors from the University of Washington and Fred Hutchinson Cancer Research Center suggest that speed is essential for controlling the COVID-19 pandemic and offer four rationales supporting their conclusion:

• Doubling the vaccine coverage with a single dose compared with a 2-dose regimen will accelerate pandemic control because even lack of complete protection on an individual level is likely to lower transmission rates enough to stop epidemic growth;
• Providing effective protection for as many people as possible is more ethical because it distributes the scarce commodity more justly;
• A single-dose vaccine approach could mitigate the higher incidence of many vaccine-associated adverse events seen with the second dose;
• And administering a vaccine that is only partly protective may reduce risky behavior such as doffing masks or eliminating social distancing.

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