Comparing hybrid and regular COVID-19 vaccine-induced immunity against the Omicron epidemic
Lei Huang, Francisco Tsz Tsun Lai, Vincent Ka Chun Yan, Franco Wing Tak Cheng, Ching Lung Cheung, Celine Sze Ling Chui, Xue Li, Eric Yuk Fai Wan, Carlos King Ho Wong, Ivan Fan‐Ngai Hung, Chak Sing Lau, Ian Chi Kei Wong, Esther W. Chan
Abstract
Evidence on the effectiveness of COVID-19 vaccines among people who recovered from a previous SARS-CoV-2 infection is warranted to inform vaccination recommendations. Using the territory-wide public healthcare and vaccination records of over 2.5 million individuals in Hong Kong, we examined the potentially differential risk of SARS-CoV-2 infection, hospitalization, and mortality between those receiving two homologous doses of BNT162b2 or CoronaVac versus those with a previous infection receiving only one dose amid the Omicron epidemic. Results show a single dose after a SARS-CoV-2 infection is associated with a lower risk of infection (BNT162b2: adjusted incidence rate ratio [IRR] = 0.475, 95% CI: 0.410-0.550; CoronaVac: adjusted IRR = 0.397, 95% CI: 0.309-0.511) and no significant difference was detected in the risk of COVID-19-related hospitalization or mortality compared with a two-dose vaccination regimen. Findings support clinical recommendations that those with a previous infection could receive a single dose to gain at least similar protection as those who received two doses without a previous infection.