Perhaps you should try some spelling variations:
vaccine research » medicine research
option research » opinion research, action research, optics research
multi option » multi location, multi population, multi ratios
anti vaccine » ant vaccine, active vaccine, aids vaccine
july 2006 » july 2008, july 2007, july 2009

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( multi option research : july 2006 ) or ( anti vaccine research : july 2006 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( multi option research : july 2006 ) OR ( anti vaccine research : july 2006 )).
• Adding a wildcard symbol may retrieve word variants: (( multi option research : july 2006 ) or ( anti vaccine research : july 2006 ))*.