Analysis suggests high efficacy for single dose of Pfizer-BioNTech vaccine

An analysis by Canadian researchers suggests that a single dose of the Pfizer-BioNTech COVID-19 vaccine is highly efficacious, according to a letter published yesterday in the New England Journal of Medicine (NEJM).

Results from the phase 3 trial of the Pfizer-BioNTech vaccine, published in NEJM on Dec 31, 2020, suggested the efficacy after the first dose of the two-dose vaccine was 52.4%, based on data collected during the first 2 weeks after the first shot to before the second shot. The overall efficacy after two doses was 94.8%.

But in their analysis of trial data submitted to the US Food and Drug Administration by Pfizer and BioNTech, researchers with the British Columbia Centre for Disease Control and the Institut National de Santé Publique du Québec found that data collected starting 2 weeks after the first shot to before the second shot indicate the efficacy of the first dose was 92.6%. The researchers suggest the initial efficacy analysis was lower because immunity was still mounting in vaccine recipients during the first 2 weeks after the first shot.

"With such a highly protective first dose, the benefits derived from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are offered at least one dose," the authors wrote.

In a response, trial investigators said that alternative dosing regimens of the Pfizer-BioNTech vaccine have not been evaluated, and that the decision to implement alternative regimens lies with health authorities.
Feb 17 N Engl J Med letter

Study highlights heart damage 1 month after severe COVID-19

More than half of patients with severe COVID-19 and elevated levels of a key marker of heart muscle damage after hospital release showed signs of damage to the heart a month later, a study today in the European Heart Journal finds.

Led by researchers from University College London, the study involved cardiac magnetic resonance imaging (MRI) of 148 COVID-19 patients who had elevated troponin levels, indicating heart damage, and who had required ventilatory support before being released from one of six London hospitals at least a month before. One in three had required mechanical ventilation.

Imaging showed inflammation of the heart muscle (26% of patients), scarring or dead heart tissue (54%), restricted blood supply to the heart (22%), or both inflammation and ischemia (6%). Eight percent showed signs of ongoing heart inflammation.

Co-author Marianna Fontana, MD, PhD, of University College London said in a European Society of Cardiology press release that elevated troponin levels are linked to worse COVID-19 outcomes and that patients with severe infections often have other heart-related medical conditions such as diabetes, high blood pressure, and obesity.

"During severe COVID-19 infection, however, the heart may also be directly affected," Fontana said. "Unpicking how the heart can become damaged is difficult, but MRI scans of the heart can identify different patterns of injury, which may enable us to make more accurate diagnoses and to target treatments more effectively."

The researchers noted that the heart damage seen on imaging may have preceded COVID-19 or have occurred as a result of infection. "While we detected only a small amount of ongoing injury, we saw injury to the heart that was present even when the heart's pumping function was not impaired and might not have been picked up by other techniques," Fontana said. "In the most severe cases, there are concerns that this injury may increase the risks of heart failure in the future, but more work is needed to investigate this further."

The authors said that the findings can also help researchers find ways of preventing heart injury in severely ill COVID-19 patients and detecting and treating blood clots associated with the virus.
Feb 18 Eur Heart J study
Feb 17 European Society of Cardiology press release

High mortality found in hospitalized COVID-19 patients with diabetes

Updated results from a study of hospitalized COVID-19 patients with diabetes shows 1 in 5 died within 28 days of hospitalization, French researchers reported yesterday in Diabetologia.

The updated results from the CORONADO (Coronavirus SARS-CoV-2 and Diabetes Outcomes) study, which evaluated outcomes in diabetic French patients hospitalized for COVID-19 from Mar 10 through Apr 10, 2020, show that among 2,796 patients, 577 (20.6%; 95% confidence interval [CI], 19.2% to 22.2%) died within 28 days of hospitalization and 1,404 (50.2%; 95% CI, 48.3% to 52.1%) were discharged from the hospital. Results presented in May 2020 showed that 10% of patients who had diabetes and COVID-19 died within 7 days of hospitalization.

The patients were mostly male (63.7%), with a mean age of 69.7 years, and the vast majority had type 2 diabetes (88.2%). Microvascular and macrovascular diabetic complications were found in 44.2% and 38.6% of patients, respectively.

In multivariable models, younger age, routine metformin therapy, and longer symptom duration were positively associated with hospital discharge, while history of microvascular complications, anticoagulant routine therapy, shortness of breath on admission, abnormal levels of liver enzymes, and higher white blood cell counts and C-reactive protein levels were associated with a lower chance of discharge and a higher risk of death. Patients receiving routine treatment with insulin and statins also had a higher risk of death.

The study authors said establishing prognostic factors for hospital discharge and death in diabetic COVID-19 patients could help clinicians better manage this population and use hospital resources accordingly.
Feb 7 Diabetologia study