Front-line

Parisians marked dusk on the first day of their coronavirus lockdown this week by stepping out on their balconies and throwing open their windows to cheer and applaud the front-line fighting of doctors and nurses of the virulent viral enemy that has upended life around the world.

"Gifts from the heart" is the theme of Jill Biden's first Christmas as first lady, and she has filled the historic home with tributes to those who have inspired her over the past year: front-line workers who soldiered through the pandemic, service members who gave their lives, and members of her family and those of previous presidents.

The bacillus Calmette-Guérin (BCG) vaccine for tuberculosis causes front-line immune cells to make long-lasting biological “marks” on their DNA, changing how they read genetic instructions for fighting off viruses, the researchers say.