Impact of COVID-19 Vaccination on Healthcare Worker Infection Rate and Outcome during SARS-CoV-2 Omicron Variant Outbreak in Hong Kong

Abstract

Immune escape is observed with SARS-CoV-2 Omicron (Pango lineage B.1.1.529), the predominant circulating strain worldwide. A booster dose was shown to restore immunity against Omicron infection; however, real-world data comparing mRNA (BNT162b2; Comirnaty) and inactivated vaccines’ (CoronaVac; Sinovac) homologous and heterologous boosting are lacking. A retrospective study was performed to compare the rate and outcome of COVID-19 in healthcare workers (HCWs) with various vaccination regimes during a territory-wide Omicron BA.2.2 outbreak in Hong Kong. During the study period from 1 February to 31 March 2022, 3167 HCWs were recruited, and 871 HCWs reported 746 and 183 episodes of significant household and non-household close contact. A total of 737 HCWs acquired COVID-19, all cases of which were all clinically mild. Time-dependent Cox regression showed that, compared with two-dose vaccination, three-dose vaccination reduced infection risk by 31.7% and 89.3% in household contact and non-household close contact, respectively. Using two-dose BNT162b2 as reference, two-dose CoronaVac recipient had significantly higher risk of being infected (HR 1.69 p < 0.0001). Three-dose BNT162b2 (HR 0.4778 p< 0.0001) and two-dose CoronaVac + BNT162b2 booster (HR 0.4862 p = 0.0157) were associated with a lower risk of infection. Three-dose CoronaVac and two-dose BNT162b2 + CoronaVac booster were not significantly different from two-dose BNT162b2. The mean time to achieve negative RT-PCR or E gene cycle threshold 31 or above was not affected by age, number of vaccine doses taken, vaccine type, and timing of the last dose. In summary, we have demonstrated a lower risk of breakthrough SARS-CoV-2 infection in HCWs given BNT162b2 as a booster after two doses of BNT162b2 or CoronaVac.

Infection of healthcare workers despite a high vaccination rate during the fifth wave of COVID-19 due to Omicron variant in Hong Kong

“…Nosocomial infection of nine HCWs was only reported in a COVID-19 outbreak in late 2020 [ 18 ]. In this study, about one-fourth of HCWs were infected in our hospital and the proportion was comparable to a private hospital of 600-bed in Hong Kong [ 28 ]. It is important to explore if the infection control measures remained appropriate to protect our HCWs.…”

“…The impact of COVID-19 vaccination on HCW infections during circulation of the SARS-CoV-2 Omicron variant has been reported previously. Using the two-dose BNT162b2 regimen as reference, two-dose CoronaVac recipients had a significantly higher risk of infection, whereas three-dose BNT162b2 and two-dose CoronaVac plus BNT162b2 booster regimens were associated with a lower risk of infection [ 28 ].…”

The Impact of Vaccination Among Hospitalized Patients with the Diagnosis of COVID-19

“…The results of a retrospective study that evaluated the rate and outcome of COVID-19 in healthcare workers with various vaccination regimens during the omicron BA.2.2 outbreak in Hong Kong showed that using two-dose Comirnaty as a reference, two-dose CoronaVac recipients had a significantly higher risk of being infected (HR=1.69, p <0.0001). Three-dose Comirnaty (HR=0.4778, p <0.0001) and two-dose CoronaVac + Comirnaty booster (HR=0.4862, p =0.0157) were associated with a lower risk of infection ( 27 , 28 ).…”

Estimation of the Effectiveness of a Tighter, Reinforced Quarantine for the Coronavirus Disease 2019 (COVID-19) Outbreak: Analysis of the Third Wave in South Korea

“…It is possible that extended and strictly enforced quarantine restrictions may place a significant financial, social, and emotional strain on the general population once the universal immunization program has been completed [ 24 , 25 , 26 ]. In light of the fact that a number of research papers have demonstrated that COVID-19 infections can be avoided by receiving vaccinations at the appropriate intervals [ 27 , 28 ], in order to effectively combat this viral illness, it is necessary to take into account the degree to which individuals have developed an immunity to COVID-19 [ 24 ].…”