Impact of vaccination on SARS-CoV-2 infections and long COVID symptoms: a cross-sectional study in China

Following the adjustment of the dynamic zero-COVID-19 strategy, China has witnessed a rapid increase in COVID-19 cases. However, the relationship between diverse vaccination statuses and the spectrum of symptom presentation, disease severity, and long-term post-COVID conditions remains to be fully understood. This study aimed to assess the impact of vaccination on the incidence of SARS-CoV-2 infections, the manifestation of acute symptoms, and the occurrence of long-term symptoms post-infection within the context of China's revised pandemic prevention and control measures. This study investigated 6,572 participants from the Yichang COVID-19 Antibody Longitudinal Survey (YC-CALS) in March 2023, focusing on demographic and health-related information, including vaccination history, infection status, and symptomatology. Univariate and multivariate analysis methods were used to determine the correlations between vaccination status and COVID-19 outcomes. Among the surveyed participants, 85.91% reported positive for SARS-CoV-2. Of those who were positive, 96.79% experienced at least one common symptom, with fever (79.34%), cough (62.56%), and fatigue (60.59%) being the most reported symptoms. Despite the high incidence of symptoms, only 2.05% of those who tested positive needed hospitalization. Importantly, symptoms such as palpitations, chest pain, and shortness of breath persisted beyond 90 days in certain individuals. Booster shots significantly reduced the risk of specific symptoms including dyspnea, eye soreness and fatigue, and gastrointestinal discomfort (P < 0.05). Vaccination beyond 12 months significantly increased symptoms such as decreased sense of smell, palpitations, and chest distress (P < 0.05). Additionally, the study found a positive correlation between the timing of vaccination and the development of long COVID symptoms, with individuals vaccinated more than 12 months prior exhibiting a higher likelihood of enduring symptoms such as fatigue (OR = 1.218, P = 0.023) and headache dizziness (OR = 1.244, P = 0.038) for over one month. The findings highlight the critical importance of vaccination in controlling the spread of COVID-19 and reducing symptoms and disease prognosis, providing important insights for future vaccine policy.