By LAURAN NEERGAARD and MATTHEW PERRONE
Americans age 50 and older can get a second COVID-19 booster if it’s been at least four months since their last vaccination. The Food and Drug Administration on Tuesday authorized an extra dose of the Pfizer or Moderna vaccine for that age group and for certain younger people with severely weakened immune systems. The Centers for Disease Control and Prevention later recommended the extra shot as an option but stopped short of urging that those eligible rush out and get it right away. The move comes at a time of great uncertainty. COVID-19 cases have dropped to low levels after the winter surge of the super-contagious omicron variant.