Higher correlation between neutralizing antibodies and surrogate neutralizing or binding antibodies in COVID-19 patients than vaccine recipients

This study determined the seropositive rates and levels of antibodies to severe acute respiratory syndrome coronavirus-2 in 50 patients and 108 vaccinees using microneutralization test (MNT), surrogate virus neutralization test (sVNT), chemiluminescent microparticle immunoassay (CMIA), and electrochemiluminescence immunoassay (ECLIA). MNT, as the reference method, employed living clade S and Delta viruses to measure neutralizing (NT) antibodies, while sVNT employed wild type strain and Delta receptor-binding domains (RBD) as the test antigens to measure sVNT antibodies. CMIA and ECLIA employed only one version of RBD to measure the binding antibodies. Our study performed S gene sequencing of the test virus to exclude undesired mutants that might lead to changes in antibody levels in MNT assay. We showed that spike protein amino acid sequences of our Delta virus contained 13 amino acid changes, with 3 related to the reduced neutralization. The MNT assay showed a significant reduction in seropositive rates and antibody levels in the patients' sera when the Delta variant replaced clade S as the test virus. In contrast, the seropositive rates determined by sVNT assay using wild type strain RBD and Delta RBD were non-significantly different, suggesting that sVNT assay could not identify the difference between the antigenicity of wild type RBD and Delta RBD. Furthermore, the correlation between the levels of NT and sVNT antibodies was moderate with the patients' sera but modest with the post-vaccination sera. The seropositive rates in the patients, as determined by CMIA or ECLIA, were not different from the MNT assay using clade S, but not Delta, as the test virus. In all analyses, the correlations between the antibody levels measured by MNT and the other 3 assays were modest to moderate, with the r-values of 0.3500-0.7882.

First Round of External Quality Assessment Scheme for SARS-CoV-2 Laboratories During the COVID-19 Pandemic in Thailand

The emergence of SARS-CoV-2 necessitated the rapid deployment of tests to diagnose COVID-19. To monitor the accuracy of testing across the COVID-19 laboratory network in Thailand, the Department of Medical Sciences under the Ministry of Public Health launched a national external quality assessment (EQA) scheme using samples containing inactivated SARS-CoV-2 culture supernatant from a predominant strain in the early phase of the Thailand outbreak. All 197 laboratories in the network participated; 93% (n=183) of which reported correct results for all 6 EQA samples. Ten laboratories reported false-negative results, mostly for samples with low viral concentrations, and 5 laboratories reported false-positive results (1 laboratory reported false positives and false negatives). An intralaboratory investigation of 14 laboratories reporting incorrect results revealed 2 main causes of error: (1) RNA contamination of the rRT-PCR reaction and (2) poor-quality RNA extraction. Specific reagent combinations were significantly associated with false-negative reports. Thailand's approach to national EQA for SARS-CoV-2 can serve as a roadmap for other countries interested in implementing a national EQA program to ensure laboratories provide accurate testing results, which is crucial in diagnosis, prevention, and control strategies. A national EQA program can be less costly and thus more sustainable than commercial EQA programs. National EQA is recommended to detect and correct testing errors and provide postmarket surveillance for diagnostic test performance.

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves

This study determined the presence of anti-SARS-CoV-2 antibodies in 4964 individuals, comprising 300 coronavirus disease-19 (COVID-19) prepandemic serum samples, 142 COVID-19 patients, 2113 individuals at risk due to their occupations, 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, and 553 Thai citizens returning after spending extended periods of time in countries with a high disease prevalence. We recruited participants between May 2020 and May 2021, which spanned the first two epidemic waves and part of the third wave of the COVID-19 outbreaks in Thailand. Their sera were tested in a microneutralization and a chemiluminescence immunoassay for IgG against the N protein. Furthermore, we performed an immunofluorescence assay to resolve discordant results between the two assays. None of the prepandemic sera contained anti-SARS-CoV-2 antibodies, while antibodies developed in 88% (15 of 17) of the COVID-19 patients at 8–14 days and in 94–100% of the patients between 15 and 60 days after disease onset. Neutralizing antibodies persisted for at least 8 months, longer than IgG antibodies. Of the 2113 individuals at risk due to their occupation, none of the health providers, airport officers, or public transport drivers were seropositive, while antibodies were present in 0.44% of entertainment workers. Among the 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, seropositivity was present in 1.9, 1.5, and 7.5% of the Bangkok residents during the three epidemic waves, respectively, and in 1.3% of the Chiang Mai people during the first epidemic wave. The antibody prevalence varied between 6.5 and 47.0% in 553 Thai people returning from high-risk countries. This serosurveillance study found a low infection rate of SARS-CoV-2 in Thailand before the emergence of the Delta variant in late May 2021. The findings support the Ministry of Public Health’s data, which are based on numbers of patients and contact tracing.

Nasopharyngeal SARS-CoV-2 Viral Load Response among COVID-19 Patients Receiving Favipiravir

We retrospectively studied nasopharyngeal SARS-CoV-2 viral load in the COVID-19 patients who were hospitalized between 13 January and 1 April 2020. Quantitative real-time reverse transcription-PCR were conducted with primers and probes targeting the ORF1ab and N genes. All patients were classified as Group 1: Received favipiravir + chloroquine or hydroxychloroquine + lopinavir/ritonavir or darunavir/ritonavir for 5-10 days, Group 2: Received chloroquine or hydroxychloroquine + lopinavir/ritonavir or darunavir/ritonavir for 5-10 days and Group 3: no anti-viral medication. Of 115 patients, 38 (33%), 54 (47%), and 23 (20%) patients were in Group 1, 2, and 3, respectively. Median (IQR) baseline viral loads at days 0 of Group 1, 2, and 3 were 7.2 (6.0-8.1), 6.9 (5.8-7.8), and 6.9 (5.8-7.6) log₁₀ copies/mL, respectively. The reductions of mean viral loads at day 3 from baseline were 2.41, 1.38,and 2.19 log₁₀ copies/mL in the corresponding groups (P <0.05). There were no differences in reductions of mean viral loads from baseline among three groups at days 5 and 10 (P >0.05). By multiple logistic regression analysis, receiving favipiravir was associated with nasopharyngeal viral load reduction at three days (P=0.001). Significant nasopharyngeal SARS-CoV-2 viral load reduction was achieved in the COVID-19 patients who received favipiravir-containing regimen.

Identification of a Novel Pathogen Using Family-Wide PCR: Initial Confirmation of COVID-19 in Thailand

In resource-limited countries, early detection of novel pathogens is often challenging, due to financial and technical constraints. This study reports the efficacy of family-wide polymerase chain reaction (PCR) in screening, detecting, and identifying initial cases of the novel SARS-CoV-2 in Thailand. Respiratory secretions were collected from suspected individuals traveling from Wuhan, China to Thailand at the beginning of January 2020. Family-wide PCR assays yielded positive results for coronavirus in one traveler within 12 h on January 8, 2020. Nucleotide sequences (290 bp) showed 100% similarity to SARS-CoV-2. The whole genome sequence was further characterized by Next Generation Sequencing (NGS) for confirmation. Combining family-wide PCR, as a rapid screening tool, with NGS, for full genome characterization, could facilitate early detection and confirmation of a novel pathogen and enable early containment of a disease outbreak.

Early transmission patterns of coronavirus disease 2019 (COVID-19) in travellers from Wuhan to Thailand, January 2020

We report two cases of coronavirus disease 2019 (COVID-19) in travellers from Wuhan, China to Thailand. Both were independent introductions on separate flights, discovered with thermoscanners and confirmed with RT-PCR and genome sequencing. Both cases do not seem directly linked to the Huanan Seafood Market in Hubei but the viral genomes are identical to four other sequences from Wuhan, suggesting early spread within the city already in the first week of January.

The safety of etomidate for emergency rapid sequence intubation of pediatric patients

OBJECTIVE

To determine whether pediatric patients given etomidate for rapid sequence intubation (RSI) in the ED develop clinically important hypotension or adrenal insufficiency.

METHODS

Retrospective review of 100 consecutive patients younger than age 10 years given etomidate for RSI in the ED at two academic medical centers. Data were abstracted from ED and in-patient medical records. Clinically important hypotension was defined as a decrease in systolic blood pressure (BP) measurement to below one standard deviation (SD) of mean normal for age. Clinically important adrenal insufficiency was defined as the need for exogenous corticosteroid replacement for suspected adrenal insufficiency at any time during hospitalization.

RESULTS

BP measurements before and within 20 minutes after etomidate administration for RSI were recorded on 84 intubations (84%). The mean change in BP between pre-intubation and post-intubation measurements was a decrease of 1 mmHg (95% CI: -6 mm Hg to +7 mm Hg, P = 0.83). When expressed as a percentage of normal BP for age, the mean change in BP was a decrease of 1% (95% CI: -7% to +6%, P = 0.82). Four patients (4.8%; 95% CI: 1.3-11.7%) had a systolic BP decrease to below one SD of mean normal for age. Fourteen patients received corticosteroids during hospitalization, but none (0/99, 95% CI: 0-3.7%) for suspected adrenal insufficiency.

CONCLUSIONS

We found no evidence of clinically important adrenocorticoid suppression and a low incidence of clinically important hypotension when using etomidate for emergent pediatric RSI. Because other induction agents may also result in hypotension, prospective comparison studies are needed to further evaluate the safety of etomidate in this patient population.