Proving you’ve been vaccinated against COVID-19 when you travel is becoming increasingly complex. How do the new set of vaccine passport apps work, and what are some of the tips and tricks to ensure that you have proof of your vaccination status when you need to? Here’s what you need...
The best method scientists have to understand with confidence how something affects something else is a randomized, controlled trial. Think of the tests currently under way to find a vaccine for COvID-19. They take a long time because the drug companies with trial va...
根据第三段"The best method scientists have to understand with confidence how something affects something else is a randomized,controlled trial.Think of the tests currently under way to find a vaccine for CO...