Perhaps you should try some spelling variations:
national research » educational research
vaccine research » medicine research
meet vaccine » media vaccine, ant vaccine, mr vaccine
july 2009 » july 2008, july 2007, july 2019
july 2011 » july 2013, july 2015, july 2019
july 2012 » july 2013

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( meet vaccine research : ((july 2009) OR (july 2011)) ) or ( sub national research : july 2012 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( meet vaccine research : ((july 2009) OR (july 2011)) ) OR ( sub national research : july 2012 )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( meet vaccine research : ((july 2009) OR (july 2011)) ) or ( sub national research : july 2012 ))".
• Adding a wildcard symbol may retrieve word variants: (( meet vaccine research : ((july 2009) OR (july 2011)) ) or ( sub national research : july 2012 ))*.