Perhaps you should try some spelling variations:
"ant vaccine research : july 2009" » "ant medicine research : july 2009", "a vaccine research : july 2009", "aids vaccine research : july 2009", "dna vaccines research : july 2009", "ant vaccine research : july 2008", "ant vaccine research : july 2007", "ant vaccine research : july 2019"
"anti vaccine research : july 2012" » "anti medicine research : july 2012", "active vaccine research : july 2012", "aids vaccine research : july 2012", "a vaccine research : july 2012", "anti vaccine research : july 2013"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("ant vaccine research : july 2009") OR ("anti vaccine research : july 2012"))~.
• Removing quotes may allow a broader search: (( ant vaccine research : july 2009 ) or ( anti vaccine research : july 2012 ))~.
• Adding a wildcard symbol may retrieve word variants: (("ant vaccine research : july 2009") or ("anti vaccine research : july 2012"))*.