Calculating an upper limit for numdays

  • Even if the NUMDAYS is null we can still calculate an upper limit for it based on the last date of the month
  • subtract the VAX_DATE from last date of month to get an upper limit for the value of numdays
  • why does this help?
    • often in vaccine safety calculations, a risk window – which is the number of days till first symptom onset – of up to 42 days is used in many calculations
    • which means even the highest possible value for the NUMDAYS upper limit is valid for these calculations