AstraZeneca faces difficult questions about its vaccine

Washington: The announcement this week that a cheap, easy-to-make coronavirus vaccine appeared to be up to 90% effective was greeted with jubilation. “Get yourself a vaccaccino,” a British tabloid celebrated, noting that the vaccine, developed by AstraZeneca and the University of Oxford, costs less than a cup of coffee. But since unveiling the preliminary results, AstraZeneca has acknowledged a key mistake in the vaccine dosage received by some study participants, adding to questions