A total of 311 participants, including 107 patients with solid tumor and 204 healthy volunteers who received 2 doses of CoronaVac were recruited from National Cancer Institute of Thailand between 2020-2021. Blood samples were collected after second dose of CoronaVac for 15 days and the neutralizing antibody (NAb) titers were detected using live-virus neutralization.SARS-CoV-2 antibody positivity was detected in 77 (72%) patients and 199 (97.5%) healthy volunteers. Antibody positivity rate was lowest (67.2%) in patients who received chemotherapy, followed by patients with post-treatment (74.2%) and patients who planned to start treatment (91.7%). Our study highlights a low degree of neutralization-afforded protection mounted by CoronaVac in cancer patients when compared with healthy volunteers, especially patients who received chemotherapy. Further booster doses, heterologous or otherwise, beyond the conventional two-dose regimen might be needed for recipients of CoronaVac to maintain a long-term anamnestic response.
