Risk of air and surface contamination during application of different noninvasive respiratory support for patients with COVID-19.

OBJECTIVES: We compared the risk of environmental contamination among patients with COVID-19 who received high-flow nasal cannula (HFNC), noninvasive ventilation (NIV), and conventional oxygen therapy (COT) via nasal cannula for respiratory failure. METHODS: Air was sampled from the hospital isolation rooms with 12 air changes/hr where 26 patients with COVID-19 received HFNC (up to 60 l/min, n = 6), NIV (n = 6), or COT (up to 5 l/min of oxygen, n = 14). Surface samples were collected from 16 patients during air sampling. RESULTS: Viral RNA was detected at comparable frequency in air samples collected from patients receiving HFNC (3/54, 5.6%), NIV (1/54, 1.9%), and COT (4/117, 3.4%) (P = 0.579). Similarly, the risk of surface contamination was comparable among patients receiving HFNC (3/46, 6.5%), NIV (14/72, 19.4%), and COT (8/59, 13.6%) (P = 0.143). An increment in the cyclic thresholds of the upper respiratory specimen prior to air sampling was associated with a reduced SARS-CoV-2 detection risk in air (odds ratio 0.83 [95% confidence interval 0.69-0.96], P = 0.027) by univariate logistic regression. CONCLUSION: No increased risk of environmental contamination in the isolation rooms was observed in the use of HFNC and NIV vs COT among patients with COVID-19 with respiratory failure. Higher viral load in the respiratory samples was associated with positive air samples.

Omicron BA.1-specific T-cell responses in adults vaccinated with CoronaVac or BNT162b2 in Hong Kong: an observational cohort study.

BACKGROUND: The primary aim of using vaccines in public health responses to SARS-CoV-2 variants of concern is to reduce incidence of severe disease, for which T-cell responses are essential. There is a paucity of data on vaccine-induced T-cell immunity to omicron (B.1.1.529). We aimed to compare SARS-CoV-2 omicron BA.1-specific T-cell responses in adults vaccinated with CoronaVac or BNT162b2. METHODS: For this observational cohort, we recruited adults (aged ≥18 years) from three vaccination centres in Hong Kong. We included participants from four cohorts (cohort 1: participants who received two doses of either BNT162b2 or CoronaVac, cohort 2: participants who received two doses and a booster, cohort 3: participants who received two doses and a booster and had a breakthrough omicron infection, and cohort 4: participants who had a previous non-omicron infection and subsequently received one dose of vaccine). People with confirmed history of COVID-19 at recruitment were excluded from cohort 1 and cohort 2. We collected blood samples before vaccination (for cohort 1 and 2), 1-month following vaccination (for all cohorts), and during convalescence for cohort 3 and 4) and determined the proportion of IFNγ+CD4+ and IFNγ+CD8+ T cells in peripheral blood against SARS-CoV-2 using flow cytometry with peptide pools of SARS-CoV-2 wild type or omicron BA.1. The primary outcome was proportion of CD4+ and CD8+ T cells against SARS-CoV-2 1 month after exposure (ie, vaccination or breakthrough infection). FINDINGS: Overall, between May 21, 2020, and Aug 31, 2021, we recruited 659 participants (231 [35%] men and 428 [65%] women). Of these participants, 428 were included in cohort 1 (214 [50%] received BNT162b2 and 214 [50%] received CoronaVac); 127 in cohort 2 (48 [38%] received all BNT162b2, 40 [31%] received all CoronaVac, and 39 [31%] received two CoronaVac and a booster with BNT162b2); 58 in cohort 3, and 46 in cohort 4 (16 [35%] received CoronaVac and 30 [65%] received BNT162b2). Vaccine-induced T-cell responses to the wild-type and omicron BA.1 variants were generally similar in adults receiving two doses of either CoronaVac (CD4+ cells p=0·33; CD8+ cells p=0·70) or BNT162b2 (CD4+ cells p=0·28; CD8+ cells p=1·0). Using a peptide pool of all structural proteins for stimulation, BNT162b2 induced a higher median frequency of omicron-specific CD4+ T cells in adults younger than 60 years (CD4+ cells 0·012% vs 0·010%, p=0·031; CD8+ cells 0·003% vs 0·000%, p=0·055) and omicron-specific CD8+ T cells in people aged 60 years or older (CD4+ cells 0·015% vs 0·006%, p=0·0070; CD8+ cells 0·007% vs 0·000%, p=0·035). A booster dose of either BNT162b2 or CoronaVac after two doses of CoronaVac boosted waning T-cell responses, but T-cell responses did not exceed those at 1 month after the second dose (CoronaVac CD4+ p=0·41, CD8+ p=0·79; BNT162b2 CD4+ p=0·70 CD8+ p=0·80). INTERPRETATION: The evidence that mRNA and inactivated vaccines based on the ancestral SARS-CoV-2 virus elicited T-cell responses to SARS-CoV-2 omicron variants might explain the high observed vaccine effectiveness against severe COVID-19 shown by both types of vaccine, despite great differences in neutralising antibody responses. The use of either vaccine can be considered if the primary aim is to reduce severity and death caused by the new omicron subvariants; however, BNT162b2 is preferable for adults older than 60 years. FUNDING: The Health and Medical Research Fund Commissioned Research on the Novel Coronavirus Disease and S H Ho Foundation.

Respiratory admissions before and during the COVID-19 pandemic with mediation analysis of air pollutants, mask-wearing and influenza rates.

BACKGROUND AND OBJECTIVE: Decline in hospitalizations for various respiratory diseases has been reported during the COVID-19 pandemic, but what led to such an observation is uncertain. METHODS: This was a territory-wide, retrospective cohort study involving all public hospital admissions in Hong Kong from 1 January 2017 to 31 December 2020. Hospital admissions for respiratory diseases, including asthma, COPD and non-COVID pneumonia, were assessed. COVID-related admissions were excluded from this study. The time of commencement of the pandemic was taken from the fourth week of January 2020. The associations between air pollutant levels, influenza and mask-wearing rates with hospital admissions were assessed by mediation analyses. RESULTS: There were altogether 19,485, 78,693 and 238,781 admissions for asthma, COPD and non-COVID pneumonia from January 2017 to December 2020. There was a marked reduction in hospital admissions of asthma, COPD and non-COVID pneumonia (37%, 36% and 12% decrease in average daily admissions, respectively) during the COVID-19 pandemic compared to before. Air pollutant levels and influenza rate were decreased while mask-wearing rate was increased. Collinearity of mask-wearing rates and pandemic year was observed. For COPD, NO2 , SO2 , PM10 and influenza rates (4%, 11%, 4% and 4% of the total effect, respectively), while for non-COVID pneumonia, PM10 and influenza rates (11% and 52%, respectively) had significant mediation effect on changes in hospital admissions before and during the COVID-19 pandemic. CONCLUSION: During the COVID-19 pandemic, a decrease in air pollutant levels and influenza rate had mediation effect on the reduction in hospitalizations of COPD and non-COVID pneumonia.

Comparison of the immunogenicity of BNT162b2 and CoronaVac COVID-19 vaccines in Hong Kong.

BACKGROUND AND OBJECTIVE: Few head-to-head evaluations of immune responses to different vaccines have been reported. METHODS: Surrogate virus neutralization test (sVNT) antibody levels of adults receiving either two doses of BNT162b2 (n = 366) or CoronaVac (n = 360) vaccines in Hong Kong were determined. An age-matched subgroup (BNT162b2 [n = 49] vs. CoronaVac [n = 49]) was tested for plaque reduction neutralization (PRNT) and spike-binding antibody and T-cell reactivity in peripheral blood mononuclear cells. RESULTS: One month after the second dose of vaccine, BNT162b2 elicited significantly higher PRNT50 , PRNT90 , sVNT, spike receptor binding, spike N-terminal domain binding, spike S2 domain binding, spike FcR binding and antibody avidity levels than CoronaVac. The geometric mean PRNT50 titres in those vaccinated with BNT162b2 and CoronaVac vaccines were 251.6 and 69.45, while PRNT90 titres were 98.91 and 16.57, respectively. All of those vaccinated with BNT162b2 and 45 (91.8%) of 49 vaccinated with CoronaVac achieved the 50% protection threshold for PRNT90. Allowing for an expected seven-fold waning of antibody titres over 6 months for those receiving CoronaVac, only 16.3% would meet the 50% protection threshold versus 79.6% of BNT162b2 vaccinees. Age was negatively correlated with PRNT90 antibody titres. Both vaccines induced SARS-CoV-2-specific CD4+ and CD8+ T-cell responses at 1 month post-vaccination but CoronaVac elicited significantly higher structural protein-specific CD4+ and CD8+ T-cell responses. CONCLUSION: Vaccination with BNT162b2 induces stronger humoral responses than CoronaVac. CoronaVac induces higher CD4+ and CD8+ T-cell responses to the structural protein than BNT162b2.