Abstract
BACKGROUND: Vaccination is one of the best ways to control the SARS-CoV-2 outbreak. In Taiwan, healthcare workers were prioritized for vaccination, but the effectiveness of these vaccines for them remains unclear. Thus, it's essential to examine their neutralizing antibodies after prime-boost vaccinations. METHODS: In this prospective observational study, 514 healthcare workers from Chang Gung Memorial hospitals in Taiwan were included between 19 March 2021 and 21 August 2021. The two doses of COVID-19 vaccines were either a match or a mixing of AZD1222 and mRNA-1273, e.g. AZD1222 + AZD1222 (n = 406), mRNA-1273 + mRNA-1273 (n = 62), and AZD1222 + mRNA-1273 (n = 46). Blood specimens were drawn after two doses of vaccines, defined as post-vaccine days [median 34.00 days and interquartile range (IQR) 29.00-42.00 days], and examined for the neutralizing antibodies via SARS-CoV-2 neutralization kits. The results were analyzed as a percentage of inhibition based on the negative control. RESULTS: After 2 vaccination doses, subjects with AZD1222 + mRNA-1273 (median 97.15%, IQR 96.06-98.06%) and mRNA-1273 + mRNA-1273 (median 97.47%, IQR 96.75-97.89%) exhibited higher neutralizing antibodies than those receiving AZD1222 + AZD1222 vaccines (median 71.28%, IQR 49.39-89.70%) (the percentage was referred to inhibition of surrogate virus). The post-vaccination days negatively impacted the neutralizing antibodies, except for the mRNA-1273 + mRNA-1273 group. The presence of fever, headache, and myalgia after the second dosage was reflected in the higher neutralizing antibodies (median of no fever 76.00% vs. fever 97.00%, p < 0.0001; median of no headache 76.00% vs. headache 95.00%, p < 0.0001; median of no myalgia 75.50% vs. myalgia 96.00%, p < 0.0001). The subjects with underlying diseases, including hypertension and cancer showed lower neutralizing antibodies (median of no hypertension 81.00% vs. hypertension 56.00%, p = 0.0029; median of no cancer 81.00% vs. cancer 56.00%, p = 0.0143). CONCLUSION: Heterologous prime-boost vaccines (AZD1222 + mRNA-1273) and two doses of mRNA vaccines are recommended. For future directions, we need to investigate the effectiveness of the vaccination against new SARS-CoV-2 variants.