Publication date: Aug 01, 2023

Although mRNA coronavirus disease 2019 (COVID-19) vaccines have been reported for high effectiveness against symptoms, it remains unclear whether post-vaccination infections are less symptomatic than infections in vaccine-naive individuals. We included patients with COVID-19 diagnosed by polymerase chain reaction tests during Japan’s alpha and delta variant epidemics. COVID-19 symptoms at approximately 4 weeks were compared based on COVID-19 vaccination status. In total, 398 cases (372 symptomatic and 26 asymptomatic; 286 unvaccinated, 66 vaccinated with one dose, and 46 with two doses) were analyzed. The most common symptoms were fever (78. 4%), fatigue (78. 4%), cough (74. 4%), loss of taste or smell (62. 8%), and headache (59. 8%). Post-vaccination infections were significantly less likely to be symptomatic. Possible confounder-adjusted odds ratios of two vaccine doses against fatigue, dry eyes and mouth, insomnia, fever, shortness of breath, unusual muscle pains, and loss of taste or smell were 0. 18 (95% confidence interval [CI]: 0. 09-0. 38), 0. 22 (95% CI: 0. 08-0. 59), 0. 33 (95% CI: 0. 14-0. 80), 0. 31 (95% CI: 0. 15-0. 63), 0. 36 (95% CI: 0. 16-0. 76), 0. 40 (95% CI: 0. 19-0. 82), and 0. 44 (95% CI: 0. 22-0. 87), respectively. Post-vaccination infections after two mRNA COVID-19 vaccine doses show milder and fewer symptoms than infections in unvaccinated patients, highlighting the effectiveness of vaccination.

Semantics

Original Article