Francisco Perez-Arce, Ph.D., from the USC Center for Economic and Social Research in Washington, D.C., and colleagues examined short-term changes in mental distress following receipt of the first dose of the COVID-19 vaccine in participants from the Understanding America Study. Surveys were conducted at regular intervals between March 10, 2020, and March 31, 2021, and the analysis included those participating in at least two waves.

The researchers found that people who were vaccinated between December 2020 and March 2021 reported decreased mental distress levels in the surveys conducted after receiving the first dose. The average effect of receiving the vaccine was equivalent to 4 percent of the standard deviation of the four-item Patient Health Questionnaire scores, a reduction in 1 percentage point (4 percent reduction from the baseline level) in the probability of being at least mildly depressed, and of 0.7 percentage points (15 percent reduction from the baseline level) in the probability of being severely depressed.

"Getting the first dose of COVID-19 resulted in significant improvements in mental health, beyond improvements already achieved since mental distress peaked in the spring of 2020," the authors write.

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