THERE  WAS A CROWDSOURCED VACCINE,   
  THAT COULD BE  CREATED REGIONALLY BY  
    MOST   PHARMACEUTICAL  COMPANIES    
   WITHOUT  MUCH EFFORT,  AND IT  WAS   
    ESTIMATED  THAT   IT  HAD  SAVED    
       TENS     OF      MILLIONS.       
                                        
 BUT IT WAS NOT OFFICIALLY RECOGNIZED  BY 
 THE  WORLD  HEALTH  ORGANIZATION, AND AS 
 SUCH  DID NOT  GIVE  WHAT THE SANCTIONED 
 (AND   UNOBTAINABLE)   ONES   DID:   THE 
 SUBSKIN  CHIP  THAT WOULD LET  YOU ENTER 
       (OR      LEAVE)     CITIES.      
                                        
  AND THAT'S WHY, EVENTUALLY, WE WOULD  
  CREATE  OUR OWN  CHIPS.  THEY  WERE   
  LARGER THAN THE OFFICIAL ONES, AND A  
   LITTLE   UNSTABLE,   AND   NEEDED    
   MAINTENANCE.  BUT   THEY   WORKED!   
  OR, THEY WOULD  WORK TOGETHER WITH A  
  LITTLE SOMETHING  TO MAKE THE  GUARD  
     LOOK    THE    OTHER     WAY.      
                                      
                                      
                                          
   BUT THE SCANNER SHOWED GREEN, SO...