Perhaps you should try some spelling variations:
vaccine research » medicine research
multiple options » multiple locations, multiple positions, multiple solutions
options research » actions research, optics research, operations research
anti vaccine » ant vaccine, active vaccine, aids vaccine
july 2007 » july 2008, july 2013, july 2012

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( anti vaccine research : july 2007 ) or ( multiple options research : july 2007 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( anti vaccine research : july 2007 ) OR ( multiple options research : july 2007 )).
• Adding a wildcard symbol may retrieve word variants: (( anti vaccine research : july 2007 ) or ( multiple options research : july 2007 ))*.