A clinical trial of a whole-virus H5N1 vaccine derived from cell culture

BACKGROUND

Widespread infections of avian species with avian influenza H5N1 virus and its limited spread to humans suggest that the virus has the potential to cause a human influenza pandemic. An urgent need exists for an H5N1 vaccine that is effective against divergent strains of H5N1 virus.

METHODS

In a randomized, dose-escalation, phase 1 and 2 study involving six subgroups, we investigated the safety of an H5N1 whole-virus vaccine produced on Vero cell cultures and determined its ability to induce antibodies capable of neutralizing various H5N1 strains. In two visits 21 days apart, 275 volunteers between the ages of 18 and 45 years received two doses of vaccine that each contained 3.75 microg, 7.5 microg, 15 microg, or 30 microg of hemagglutinin antigen with alum adjuvant or 7.5 microg or 15 microg of hemagglutinin antigen without adjuvant. Serologic analysis was performed at baseline and on days 21 and 42.

RESULTS

The vaccine induced a neutralizing immune response not only against the clade 1 (A/Vietnam/1203/2004) virus strain but also against the clade 2 and 3 strains. The use of adjuvants did not improve the antibody response. Maximum responses to the vaccine strain were obtained with formulations containing 7.5 microg and 15 microg of hemagglutinin antigen without adjuvant. Mild pain at the injection site (in 9 to 27% of subjects) and headache (in 6 to 31% of subjects) were the most common adverse events identified for all vaccine formulations.

CONCLUSIONS

A two-dose vaccine regimen of either 7.5 microg or 15 microg of hemagglutinin antigen without adjuvant induced neutralizing antibodies against diverse H5N1 virus strains in a high percentage of subjects, suggesting that this may be a useful H5N1 vaccine. (ClinicalTrials.gov number, NCT00349141.)

Safety and Immunogenicity of a Tetravalent Dengue Vaccine Candidate in Healthy Children and Adults in Dengue-Endemic Regions: A Randomized, Placebo-Controlled Phase 2 Study

BACKGROUND

A safe, effective tetravalent dengue vaccine is a global health priority. The safety and immunogenicity of a live attenuated, recombinant tetravalent dengue vaccine candidate (TDV) were evaluated in healthy volunteers from dengue-endemic countries.

METHODS

This multicenter, double-blind, phase 2 study was conducted in Puerto Rico, Colombia, Singapore, and Thailand. During stage I, 148 volunteers aged 1.5-45 years were sequentially enrolled into 4 age-descending groups and randomized at a ratio of 2:1 to receive TDV or placebo. In stage II (group 5), 212 children aged 1.5-11 years were randomized at a ratio of 3:1 to receive TDV or placebo. Participants received a subcutaneous injection of TDV or placebo on days 0 and 90 and were followed for analysis of safety, seropositivity, and neutralizing antibodies to DENV-1-4.

RESULTS

Injection site pain, itching, and erythema (mostly mild) were the only solicited adverse events more frequently reported with TDV than with placebo in all age groups. After 2 TDV doses, seropositivity was >95% in all 5 groups for DENV-1-3 and 72.7%-100% for DENV-4; geometric mean titers ranged from 582 to 1187 for DENV-1, from 582 to 1187 for DENV-2, from 196 to 630 for DENV-3, and from 41 to 210 for DENV-4 among the 5 groups.

CONCLUSIONS

TDV was well tolerated and immunogenic in volunteers aged 1.5-45 years, irrespective of prevaccination dengue exposure.

Epidemiology and clinical outcome of enterococcal bacteraemia in an acute care hospital

OBJECTIVE

To determine the epidemiology and clinical outcome of enterococcal bacteraemia in an acute care hospital.

MATERIALS AND METHODS

This is a retrospective study on enterococcal bacteraemia in an acute hospital from January 1999 to June 2001. Patients' clinical case notes were reviewed and their demographic, clinical and microbiological data were recorded.

RESULTS

A total of 42 patients (25 males and 17 females) were included in the study, their mean age was 74.8+/-10.9 years. The majority of them had underlying diabetes mellitus and neurological disease. Seventeen patients required intensive care. Sources of enterococcal bacteraemia were identified in 21 cases (urinary tract, 13 patients; hepatobiliary, five; cardiovascular, two and soft tissues, one patient). Eighteen patients had prior invasive procedures. All the Enterococcus species isolated were vancomycin-susceptible; however, eight were ampicillin-resistant and 13 had high-level gentamicin resistance. Shock, disseminated intravascular coagulopathy, acute renal failure and cardiorespiratory arrest occurred in 42% of the cases. Antibiotics were prescribed appropriately in 31 patients and seven deaths were recorded. Of the 11 patients who received inappropriate therapy, six deaths were recorded. Inappropriate antibiotic therapy was associated with mortality. The mortality rate was 31%. Only one patient had a relapse of enterococcal bacteraemia from urinary tract infection secondary to underlying ureteric stricture. There were no vancomycin resistant cases.

CONCLUSION

Urinary tract infection was the most common source of enterococcal bacteraemia. Appropriate antibiotics were essential in treating bacteraemia to reduce mortality. Vancomycin-resistant Enterococcus was not detected. The presence of comorbid conditions and invasive procedures in patients with enterococcal bacteraemia were found in 86 and 71% of patients, respectively.

A phase II randomized study to determine the safety and immunogenicity of the novel PIKA rabies vaccine containing the PIKA adjuvant using an accelerated regimen

BACKGROUND

Human Rabies infection continues to be potentially fatal despite the availability of post-exposure prophylaxis with rabies vaccine. The PIKA Rabies vaccine adjuvant is a TLR3 agonist and has been shown to be safe and immunogenic in clinical phase I studies.

METHODS

We conducted a phase II, open label, randomized study in healthy adults to assess the safety and immunogenicity of the PIKA rabies vaccine under an accelerated regimen. 126 subjects were randomized into two groups: control vaccine classic regimen ("control-classic") and PIKA vaccine accelerated regimen ("PIKA-accelerated"). Subjects were followed up for safety and rabies virus neutralizing antibodies (RVNA).

RESULTS

Both the control and PIKA vaccines were generally well tolerated. 57.6% of subjects in the PIKA vaccine group, compared with 43.8% of subjects in the control-classic group, achieved the target RVNA titer of ≥0.5 IU/mL by Day 7. All subjects achieved the target RVNA titer by Day 14. The RVNA geometric mean titer at Day 7 was 0.60 IU/ml in the PIKA vaccine group and 0.39 IU/ml in the control-classic group. At Day 14, the RVNA geometric mean titer was 18.25 IU/ml in the PIKA-accelerated group and 19.24 IU/ml in the control-classic group. The median time taken to reach the target RVNA titer level of ≥0.5 IU/mL was 7.0 days (95% CI: 7.0-42.0 days) in the PIKA-accelerated group and 14.0 days (95% CI: 7.0-42.0 days) in the control-classic group.

CONCLUSION

The accelerated regimen using the investigational PIKA Rabies vaccine was well-tolerated and demonstrated non-inferior immunogenicity compared to the classic regimen using the commercially available vaccine in healthy adults. Clinical trial registry: The study was registered with clinicaltrials.gov (NCT02956421).

Performance of an automated chemiluminescence SARS-CoV-2 IG-G assay

INTRODUCTION

We describe our evaluation of the Abbott SARS-CoV-2 IgG assay on the Architect immunoassay analyser.

METHODS

We assessed assay precision, sensitivity, specificity, positive/negative predictive values (PPV/NPV), cross-reactivity (influenza/dengue/hepatitis B and C/rheumatoid factor/anti-nuclear/double-stranded DNA/syphilis) and sample throughput in samples from real-time polymerase chain reaction (RT-PCR) positive patients/healthcare workers (HCWs)/pre-pandemic samples. We compared the cut-off indexes (COIs) between all control samples (HCWs and pre-pandemic) to generate an optimised COI limit for reactivity.

RESULTS

The assay specificity was 99.8% (n = 980) and sensitivity was 45.9-96.7% (n = 279). When tested ≥ 14 days post-positive RT-PCR (POS), the PPV/NPV was 96.4%/99.8%. The difference between the COIs of HCWs/pre-pandemic samples was small (0.01, p < 0.0001). There was minimal cross-reactivity with other antibodies. A lower COI limit for reactivity (≥0.55, using the 99th percentile COI of our controls and ROC analysis) improved diagnostic sensitivity, especially at 0-6 days POS (45.9-55.8%), with a small decrease in specificity (98.9%). The assay throughput was 100 samples in 70 min.

CONCLUSION

The Abbott SARS-CoV-2 IgG assay shows excellent performance in patients ≥ 14 days POS. The difference between the COIs of HCWs and pre-pandemic samples was numerically small. A lower COI limit improves assay sensitivity with a slight decrease in specificity.

Atypical SARS in geriatric patient

We describe an atypical presentation of severe acute respiratory syndrome (SARS) in a geriatric patient with multiple coexisting conditions. Interpretation of radiographic changes was confounded by cardiac failure, with resolution of fever causing delayed diagnosis and a cluster of cases. SARS should be considered even if a contact history is unavailable, during an ongoing outbreak.

Melioidosis complicated by pericarditis

Melioidosis is a bacterial infection caused by the Gram-negative bacillus Burkholderia pseudomallei. We report an unusual case of melioidosis that presented as a pyrexia of unknown origin complicated by pericardial effusion. Our patient received a 6-week course of intravenous antibiotics, followed by 8 months of oral antibiotics, and made a complete recovery. This report illustrates the diagnostic and therapeutic challenge that clinicians may encounter when faced with this potentially fatal infection.

Extended-spectrum beta-lactamases in clinical isolates of Escherichia coli and Klebsiella spp. in a Singapore hospital: clinical spectrum

INTRODUCTION

The rising prevalence of extended-spectrum beta-lactamases in gram-negative bacillary pathogens is an important clinical problem resulting from the extensive use of broad-spectrum antibiotics. The emergence of the extended-spectrum beta-lactamases increases the possibility that traditional, empiric antimicrobial regimens may be ineffective. The aims of this study are: to determine the epidemiologic characteristics and clinical outcome of patients diagnosed with infection caused by Klebsiella spp. and Escherichia coli producing extended-spectrum beta-lactamases; to define a subgroup of patients who may benefit from early, empiric therapy; and to determine the local antibiotic sensitivity pattern in order to improve antibiotic utilisation in our hospital.

MATERIALS AND METHODS

A 4-month retrospective review of patients hospitalised in Changi General Hospital between November 2000 and February 2001 who were diagnosed with infection caused by isolates of Klebsiella spp. or Escherichia coli producing extended-spectrum beta-lactamases.

RESULTS

During the study period, 44 % of Klebsiella spp. and 16.1 % of Escherichia coli isolates were reported as producers of the extended-spectrum beta-lactamases. Sixty-eight patients were assessed to have clinically significant infection caused by 75 isolates. Most of them were elderly, had multiple medical problems and were recently treated with beta-lactam antibiotics. There was a trend toward better outcome in patients who received adequate initial, empiric therapy.

CONCLUSION

Patients with infections caused by extended-spectrum beta-lactamase producing Enterobacteriaceae have certain identifiable, common clinical characteristics. In our institution, only carbapenems remain effective against all isolates of Klebsiella spp. or Escherichia coli producing extended-spectrum beta-lactamases. Further research is necessary to define a group of patients who can benefit from an early, broad-spectrum, empiric therapy.

Evaluation of intensive care unit-acquired urinary tract infections in Singapore

INTRODUCTION

Urinary tract infections remain one of the most frequently encountered acquired complications in an intensive care unit (ICU). The objective of this study was to determine the incidence, risk factors, microbial sensitivity patterns, and clinical outcomes of patients with UTIs acquired during their admission to an ICU in an acute care hospital in Singapore.

MATERIALS AND METHODS

This was a 14-week prospective study. All ICU patients > or =18 years who remained in the ICU for > or =48 hours were eligible for this study. Patients were reviewed daily and the presence of an ICU-acquired UTI was identified via urinary microscopic examination or culture results. Other data collected included patient demographics, ICU admission criteria, concomitant illnesses, presence of invasive lines, microbial sensitivity and treatment outcomes.

RESULTS

Thirty-fi ve (13.7%) cases of ICU-acquired UTI occurred in 256 separate ICU admissions. The most common micro-organisms isolated were Candida spp. (34%). Female gender and prior exposure to antibiotics were independent risk factors for developing an ICU-acquired UTI (P <0.01). Both mean length of ICU stay and duration of catheterisation were significantly longer for patients with ICU-acquired UTI (P <0.001). The mortality rate of patients with ICU-acquired UTIs (12.1%) was slightly higher than those without (9.9%).

CONCLUSIONS

The incidence of ICU-acquired UTIs was similar to figures reported for nosocomial UTIs from the previous studies. Significant risk factors for developing an ICU-acquired UTI were female gender and history of antibiotic exposure prior to ICU admission. The insignificant link between ICU-acquired UTI and mortality requires further investigation in larger cohorts.

Reflections on COVID-19: A Literature Review of SARS-CoV-2 Testing

Although the Coronavirus disease 2019 (COVID-19) pandemic has ended, there are still many important lessons we can learn, as the pandemic profoundly affected every area of laboratory practice. During the pandemic, extensive changes to laboratory staffing had to be implemented, as many healthcare institutions required regular screening of all healthcare staff. Several studies examined the effectiveness of different screening regimens and concluded that repeated testing, even with lower sensitivity tests, could rival the performance of gold-standard RT-PCR testing in the detection of new cases. Many assay evaluations were performed both in the earlier and later periods of the pandemic. They included both nucleocapsid/spike antibodies and automated antigen assays. Early in the pandemic, it was generally agreed that the initial nucleocapsid antibody assays had poor sensitivity when used before 14 days of disease onset, with total or IgG antibodies being preferred over the use of IgM. Spike antibody assays gradually replaced nucleocapsid antibody assays, as most people were vaccinated. Spike antibodies tracked the rise in antibodies after vaccination with mRNA vaccines and became invaluable in the assessment of vaccine response. Studies demonstrated robust antibody secretion with each vaccine dose and could last for several months post-vaccination. When antigen testing was introduced, they became effective tools to identify affected patients when used serially or in an orthogonal fashion with RT-PCR testing. Despite the numerous findings during the pandemic period, research in COVID-19 has slowed. To this day it is difficult to identify a true neutralizing antibody test for the virus. An appropriate antibody level that would confer protective immunity against the plethora of new variants remains elusive. We hope that a summary of events during the pandemic could provide important insights to consider in planning for the next viral pandemic.

Localised outbreak of Falciparum malaria in Singapore

Malaria is primarily an imported disease in Singapore. Local outbreaks are uncommon. We describe a localised outbreak of three patients with Falciparum malaria, which we believe to be locally acquired. There was one fatality due to severe disease and late presentation. Malaria should be considered as a cause of febrile illness as the likelihood of cure depends on early detection and treatment.

Influenza A H1N1 (2009): clinical spectrum of disease among adult patients admitted to a regional hospital in Singapore

INTRODUCTION

The worldwide spread of Influenza A H1N1 (2009) has proceeded at an unprecedented rate, with the World Health Organization rapidly raising its influenza pandemic alert to phase six. We describe the disease spectrum of H1N1 (2009) to aid the triaging and identification of patients at risk.

METHODS

This is a retrospective chart review of all confirmed H1N1 (2009) cases admitted to our institution between June and September 2009.

RESULTS

The disease severity of the 153 patients studied was classified as mild (n is 75), moderate (n is 55) and severe (n is 23). 81 patients were female. The median age was 26 years. While comorbidities were more prevalent among patients with moderate-severe illness, 47.4 percent reported no pre-existing illness. Presenting complaints of breathlessness, tachycardia, low-pulse oximetry, higher leukocyte counts and C-reactive protein with low albumin levels were more commonly noted in moderate-severe illness (p-value less than 0.001). All patients received oseltamivir at a median of four days from illness onset. 18 required intensive care unit admission, with the majority (94.4 percent) within the first 24 hours of hospitalisation. The overall mortality rate was 4.6 percent. Median lengths of hospitalisation were four and nine days for moderate and severe cases, respectively.

CONCLUSION

While the majority of H1N1 (2009) patients have mild illness, a subgroup can become critically ill. Prior good health is not necessarily a good discriminator against severe illness. The presence of dyspnoea, tachycardia and desaturation at triage should heighten the index of suspicion for H1N1 (2009)-related complications.

Dapsone hypersensitivity syndrome masquerading as a viral exanthem: three cases and a mini-review

INTRODUCTION

We report 3 cases of dapsone hypersensitivity syndrome due to anti-malarial chemoprophylactic treatment with maloprim, in military servicemen, presenting like a viral exanthem.

CLINICAL PICTURE

Three male military recruits presented with fever and rash, 6 to 8 weeks after commencing on weekly doses of maloprim.

TREATMENT

A course of topical and systemic corticosteroids and oral antihistamines were started.

OUTCOME

All cases showed gradual resolution of fever, rash and eventual normalisation of liver function test.

CONCLUSION

A high index of suspicion was required before this uncommon syndrome can be recognised. Early institution of corticosteroid therapy and discontinuation of maloprim are the mainstays of treatment.

A case of right loin pain: septic ovarian vein thrombosis due to Campylobacter fetus bacteraemia

INTRODUCTION

Septic ovarian venous thrombosis is an uncommon condition. Diagnosis is often not immediately apparent clinically and there are many that mimic this condition. We described an unusual case of septic ovarian vein thrombosis associated with Campylobacter fetus (C. fetus) bacteraemia.

CLINICAL PICTURE

A 46-year-old female presented with fever and acute right loin pain. Right ovarian venous thrombosis was demonstrated on sonography and confirmed with computed tomography and magnetic resonance imaging. C. fetus was isolated from the blood.

TREATMENT AND OUTCOME

The patient was given antibiotics and anticoagulation therapy with good response.

CONCLUSION

Septic ovarian vein thrombosis should be considered as a differential diagnosis in female patients presenting with fever associated with lower abdominal pain. C. fetus bacteraemia also predisposes to thrombophlebitis, including septic ovarian vein thrombosis. When they are diagnosed in a timely manner and treated appropriately, the response is good and potential serious complications, including thromboembolism, and death could be averted. Radiological imaging is useful in the diagnostic work-up of this condition.