Safety and Immunogenicity of a Booster Vaccination by CoronaVac or BNT162b2 in Previously Two-Dose Inactivated Virus Vaccinated Individuals with Negative Neutralizing Antibody.

COVID-19 has swept across the globe since 2019 and repeated waves of infection have been caused by different variants of the original SARS-CoV-2 (wild type), with the Omicron and Delta variants having dominated recently. Vaccination is among the most important measures in the absence of widespread use of antivirals for prevention of morbidity and mortality. Inactivated virus vaccine has been abundantly used in many countries as the primary two-dose regimen. We aim to study the safety and immunogenicity of CoronaVac (three-dose inactivated virus vaccine) and the BNT162b2 (two-dose inactivated virus vaccine followed by an mRNA vaccine) booster. Both CoronaVac and BNT162b2 boosters are generally safe and have good immunogenicity against the wild type SARS-CoV-2 and the Delta variant with the majority having neutralizing antibodies (NAb) on day 30 and day 90. However, the BNT162b2 booster is associated with a much higher proportion of positive NAb against the Omicron variant. Only 8% of day 30 and day 90 samples post CoronaVac booster have NAb against the Omicron variant. In addition, more BNT162b2 booster recipients are having positive T-cell responses using interferon gamma release assay. In places using inactivated virus vaccine as the primary two-dose scheme, the heterologous mRNA vaccine booster is safe and more immunogenic against the Omicron variant and should be considered as a preferred option during the current outbreak.

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

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.

Evaluation of the performance of a modified Acute Physiology and Chronic Health Evaluation (APACHE II) scoring system for critically ill patients in emergency departments in Hong Kong.

INTRODUCTION: Numerous prognostic predictive models have been developed for critically ill patients, many of which are primarily designed for use in intensive care units. The objective of this study was to evaluate the accuracy of a modified Acute Physiology and Chronic Health Evaluation (APACHE II) scoring system in predicting the mortality for critically ill patients managed in emergency department (ED) resuscitation rooms in Hong Kong. METHOD: A multi-centre, prospective study was conducted for patients managed in the resuscitation rooms of the EDs of four major hospitals, including one university teaching hospital. The primary outcome measure was 14 day all-cause mortality and the secondary outcome measure was the length of stay in hospital. RESULTS: Of 867 patients recruited between 4 and 30 April 2004, 106 (12.2%) patients died. The modified APACHE II score was found to be significantly higher in non-survivors compared to survivors (mean+/-S.D.: 21.2+/-7.7 versus 14.4+/-7.1, p<0.001). The area under the curve for modified APACHE II in predicting mortality was 0.743 (95% CI, 0.696-0.790). CONCLUSION: The modified APACHE II score is only a moderate predictor of mortality for critically ill patients managed in the resuscitation rooms of EDs in Hong Kong. A more ED specific scoring method is required.

A loophole in international quarantine procedures disclosed during the SARS crisis.

This study describes a loophole in the international quarantine system during the recent Asian severe acute respiratory syndrome (SARS) outbreak. Specifically, that of travelers disguising symptoms of respiratory tract infection at international airports, in order to board aircraft to return to their home countries-notwithstanding the infection risks this involves to others. High medical fees for treatment to non-residents in epidemic areas were found to be the main cause for this behaviour. This phenomenon revealed a loophole in the control mechanisms of international quarantine procedures, letting travelers carrying a highly contagious virus slip by undetected and causing possible multi-country outbreaks of communicable diseases. Clinical evidence collected from medical records at medical centers can highlight this oversight.

Aeromedical evacuation of injured hikers in Hong Kong.

BACKGROUND: Hiking is a very popular sport in Hong Kong. Serious injuries can sometimes occur in the remote areas not accessible to roads. Aeromedical evacuation service is run by the Government Flying Service (GFS) with emergency physicians and nurses as volunteers in Hong Kong. In this paper we describe the profile and outcome of injured hikers rescued by the GFS. METHODS: In this retrospective review, nature of the complaints, medical team composition, vital signs, clinical assessment and diagnosis on site were collected from the GFS medical record. Demographic data, final diagnoses and outcomes of the patients were retrieved from emergency department (ED) and hospital discharge records. RESULTS: A total of 275 cases were recruited for the 3-year period from January 2003 to December 2005. The mean age of the group was 39 years (range 1-83) with more males (159, 58%) than females. Heat illnesses, injuries and medical problems each constituted about one third of the cases. Lower limb injuries accounted for nearly half of the injuries. About 30% of the rescued hikers did not register to be seen at the ED. Only 48 hikers (17.5%) required admission and four were admitted to intensive/coronary care units for heat stroke and acute coronary syndrome. Five cases of pre-hospital cardiac arrest were recorded. CONCLUSION: Most hikers evacuated by the GFS did not suffer from serious conditions. GFS should still be prepared for the occasional cases that require advanced life support.